Xavier Hernandez
2016-Apr-21 12:34 UTC
[Gluster-users] disperse volume file to subvolume mapping
Can you try a 'gluster volume rebalance v0 start force' ? On 21/04/16 14:23, Serkan ?oban wrote:>> Has the rebalance operation finished successfully ? has it skipped any files ? > Yes according to gluster v rebalance status it is completed without any errors. > rebalance status report is like: > Node Rebalanced files size Scanned > failures skipped > 1.1.1.185 158 29GB 1720 > 0 314 > 1.1.1.205 93 46.5GB 761 > 0 95 > 1.1.1.225 74 37GB 779 > 0 94 > > > All other hosts has 0 values. > > I double check that files with '---------T' attributes are there, > maybe some of them deleted but I still see them in bricks... > I am also concerned why part files not distributed to all 60 nodes? > Rebalance should do that? > > On Thu, Apr 21, 2016 at 1:55 PM, Xavier Hernandez <xhernandez at datalab.es> wrote: >> Hi Serkan, >> >> On 21/04/16 12:39, Serkan ?oban wrote: >>> >>> I started a gluster v rebalance v0 start command hoping that it will >>> equally redistribute files across 60 nodes but it did not do that... >>> why it did not redistribute files? any thoughts? >> >> >> Has the rebalance operation finished successfully ? has it skipped any files >> ? >> >> After a successful rebalance all files with attributes '---------T' should >> have disappeared. >> >> >>> >>> On Thu, Apr 21, 2016 at 11:24 AM, Xavier Hernandez >>> <xhernandez at datalab.es> wrote: >>>> >>>> Hi Serkan, >>>> >>>> On 21/04/16 10:07, Serkan ?oban wrote: >>>>>> >>>>>> >>>>>> I think the problem is in the temporary name that distcp gives to the >>>>>> file while it's being copied before renaming it to the real name. Do >>>>>> you >>>>>> know what is the structure of this name ? >>>>> >>>>> >>>>> Distcp temporary file name format is: >>>>> ".distcp.tmp.attempt_1460381790773_0248_m_000001_0" and the same >>>>> temporary file name used by one map process. For example I see in the >>>>> logs that one map copies files part-m-00031,part-m-00047,part-m-00063 >>>>> sequentially and they all use same temporary file name above. So no >>>>> original file name appears in temporary file name. >>>> >>>> >>>> >>>> This explains the problem. With the default options, DHT sends all files >>>> to >>>> the subvolume that should store a file named 'distcp.tmp'. >>>> >>>> With this temporary name format, little can be done. >>>> >>>>> >>>>> I will check if we can modify distcp behaviour, or we have to write >>>>> our mapreduce procedures instead of using distcp. >>>>> >>>>>> 2. define the option 'extra-hash-regex' to an expression that matches >>>>>> your temporary file names and returns the same name that will finally >>>>>> have. >>>>>> Depending on the differences between original and temporary file names, >>>>>> this >>>>>> option could be useless. >>>>>> 3. set the option 'rsync-hash-regex' to 'none'. This will prevent the >>>>>> name conversion, so the files will be evenly distributed. However this >>>>>> will >>>>>> cause a lot of files placed in incorrect subvolumes, creating a lot of >>>>>> link >>>>>> files until a rebalance is executed. >>>>> >>>>> >>>>> >>>>> How can I set these options? >>>> >>>> >>>> >>>> You can set gluster options using: >>>> >>>> gluster volume set <volname> <option> <value> >>>> >>>> for example: >>>> >>>> gluster volume set v0 rsync-hash-regex none >>>> >>>> Xavi >>>> >>>> >>>>> >>>>> >>>>> >>>>> On Thu, Apr 21, 2016 at 10:00 AM, Xavier Hernandez >>>>> <xhernandez at datalab.es> wrote: >>>>>> >>>>>> >>>>>> Hi Serkan, >>>>>> >>>>>> I think the problem is in the temporary name that distcp gives to the >>>>>> file >>>>>> while it's being copied before renaming it to the real name. Do you >>>>>> know >>>>>> what is the structure of this name ? >>>>>> >>>>>> DHT selects the subvolume (in this case the ec set) on which the file >>>>>> will >>>>>> be stored based on the name of the file. This has a problem when a file >>>>>> is >>>>>> being renamed, because this could change the subvolume where the file >>>>>> should >>>>>> be found. >>>>>> >>>>>> DHT has a feature to avoid incorrect file placements when executing >>>>>> renames >>>>>> for the rsync case. What it does is to check if the file matches the >>>>>> following regular expression: >>>>>> >>>>>> ^\.(.+)\.[^.]+$ >>>>>> >>>>>> If a match is found, it only considers the part between parenthesis to >>>>>> calculate the destination subvolume. >>>>>> >>>>>> This is useful for rsync because temporary file names are constructed >>>>>> in >>>>>> the >>>>>> following way: suppose the original filename is 'test'. The temporary >>>>>> filename while rsync is being executed is made by prepending a dot and >>>>>> appending '.<random chars>': .test.712hd >>>>>> >>>>>> As you can see, the original name and the part of the name between >>>>>> parenthesis that matches the regular expression are the same. This >>>>>> causes >>>>>> that, after renaming the temporary file to its original filename, both >>>>>> files >>>>>> will be considered to belong to the same subvolume by DHT. >>>>>> >>>>>> In your case it's very probable that distcp uses a temporary name like >>>>>> '.part.<number>'. In this case the portion of the name used to select >>>>>> the >>>>>> subvolume is always 'part'. This would explain why all files go to the >>>>>> same >>>>>> subvolume. Once the file is renamed to another name, DHT realizes that >>>>>> it >>>>>> should go to another subvolume. At this point it creates a link file >>>>>> (those >>>>>> files with access rights = '---------T') in the correct subvolume but >>>>>> it >>>>>> doesn't move it. As you can see, this kind of files are better >>>>>> balanced. >>>>>> >>>>>> To solve this problem you have three options: >>>>>> >>>>>> 1. change the temporary filename used by distcp to correctly match the >>>>>> regular expression. I'm not sure if this can be configured, but if this >>>>>> is >>>>>> possible, this is the best option. >>>>>> >>>>>> 2. define the option 'extra-hash-regex' to an expression that matches >>>>>> your >>>>>> temporary file names and returns the same name that will finally have. >>>>>> Depending on the differences between original and temporary file names, >>>>>> this >>>>>> option could be useless. >>>>>> >>>>>> 3. set the option 'rsync-hash-regex' to 'none'. This will prevent the >>>>>> name >>>>>> conversion, so the files will be evenly distributed. However this will >>>>>> cause >>>>>> a lot of files placed in incorrect subvolumes, creating a lot of link >>>>>> files >>>>>> until a rebalance is executed. >>>>>> >>>>>> Xavi >>>>>> >>>>>> >>>>>> On 20/04/16 14:13, Serkan ?oban wrote: >>>>>>> >>>>>>> >>>>>>> >>>>>>> Here is the steps that I do in detail and relevant output from bricks: >>>>>>> >>>>>>> I am using below command for volume creation: >>>>>>> gluster volume create v0 disperse 20 redundancy 4 \ >>>>>>> 1.1.1.{185..204}:/bricks/02 \ >>>>>>> 1.1.1.{205..224}:/bricks/02 \ >>>>>>> 1.1.1.{225..244}:/bricks/02 \ >>>>>>> 1.1.1.{185..204}:/bricks/03 \ >>>>>>> 1.1.1.{205..224}:/bricks/03 \ >>>>>>> 1.1.1.{225..244}:/bricks/03 \ >>>>>>> 1.1.1.{185..204}:/bricks/04 \ >>>>>>> 1.1.1.{205..224}:/bricks/04 \ >>>>>>> 1.1.1.{225..244}:/bricks/04 \ >>>>>>> 1.1.1.{185..204}:/bricks/05 \ >>>>>>> 1.1.1.{205..224}:/bricks/05 \ >>>>>>> 1.1.1.{225..244}:/bricks/05 \ >>>>>>> 1.1.1.{185..204}:/bricks/06 \ >>>>>>> 1.1.1.{205..224}:/bricks/06 \ >>>>>>> 1.1.1.{225..244}:/bricks/06 \ >>>>>>> 1.1.1.{185..204}:/bricks/07 \ >>>>>>> 1.1.1.{205..224}:/bricks/07 \ >>>>>>> 1.1.1.{225..244}:/bricks/07 \ >>>>>>> 1.1.1.{185..204}:/bricks/08 \ >>>>>>> 1.1.1.{205..224}:/bricks/08 \ >>>>>>> 1.1.1.{225..244}:/bricks/08 \ >>>>>>> 1.1.1.{185..204}:/bricks/09 \ >>>>>>> 1.1.1.{205..224}:/bricks/09 \ >>>>>>> 1.1.1.{225..244}:/bricks/09 \ >>>>>>> 1.1.1.{185..204}:/bricks/10 \ >>>>>>> 1.1.1.{205..224}:/bricks/10 \ >>>>>>> 1.1.1.{225..244}:/bricks/10 \ >>>>>>> 1.1.1.{185..204}:/bricks/11 \ >>>>>>> 1.1.1.{205..224}:/bricks/11 \ >>>>>>> 1.1.1.{225..244}:/bricks/11 \ >>>>>>> 1.1.1.{185..204}:/bricks/12 \ >>>>>>> 1.1.1.{205..224}:/bricks/12 \ >>>>>>> 1.1.1.{225..244}:/bricks/12 \ >>>>>>> 1.1.1.{185..204}:/bricks/13 \ >>>>>>> 1.1.1.{205..224}:/bricks/13 \ >>>>>>> 1.1.1.{225..244}:/bricks/13 \ >>>>>>> 1.1.1.{185..204}:/bricks/14 \ >>>>>>> 1.1.1.{205..224}:/bricks/14 \ >>>>>>> 1.1.1.{225..244}:/bricks/14 \ >>>>>>> 1.1.1.{185..204}:/bricks/15 \ >>>>>>> 1.1.1.{205..224}:/bricks/15 \ >>>>>>> 1.1.1.{225..244}:/bricks/15 \ >>>>>>> 1.1.1.{185..204}:/bricks/16 \ >>>>>>> 1.1.1.{205..224}:/bricks/16 \ >>>>>>> 1.1.1.{225..244}:/bricks/16 \ >>>>>>> 1.1.1.{185..204}:/bricks/17 \ >>>>>>> 1.1.1.{205..224}:/bricks/17 \ >>>>>>> 1.1.1.{225..244}:/bricks/17 \ >>>>>>> 1.1.1.{185..204}:/bricks/18 \ >>>>>>> 1.1.1.{205..224}:/bricks/18 \ >>>>>>> 1.1.1.{225..244}:/bricks/18 \ >>>>>>> 1.1.1.{185..204}:/bricks/19 \ >>>>>>> 1.1.1.{205..224}:/bricks/19 \ >>>>>>> 1.1.1.{225..244}:/bricks/19 \ >>>>>>> 1.1.1.{185..204}:/bricks/20 \ >>>>>>> 1.1.1.{205..224}:/bricks/20 \ >>>>>>> 1.1.1.{225..244}:/bricks/20 \ >>>>>>> 1.1.1.{185..204}:/bricks/21 \ >>>>>>> 1.1.1.{205..224}:/bricks/21 \ >>>>>>> 1.1.1.{225..244}:/bricks/21 \ >>>>>>> 1.1.1.{185..204}:/bricks/22 \ >>>>>>> 1.1.1.{205..224}:/bricks/22 \ >>>>>>> 1.1.1.{225..244}:/bricks/22 \ >>>>>>> 1.1.1.{185..204}:/bricks/23 \ >>>>>>> 1.1.1.{205..224}:/bricks/23 \ >>>>>>> 1.1.1.{225..244}:/bricks/23 \ >>>>>>> 1.1.1.{185..204}:/bricks/24 \ >>>>>>> 1.1.1.{205..224}:/bricks/24 \ >>>>>>> 1.1.1.{225..244}:/bricks/24 \ >>>>>>> 1.1.1.{185..204}:/bricks/25 \ >>>>>>> 1.1.1.{205..224}:/bricks/25 \ >>>>>>> 1.1.1.{225..244}:/bricks/25 \ >>>>>>> 1.1.1.{185..204}:/bricks/26 \ >>>>>>> 1.1.1.{205..224}:/bricks/26 \ >>>>>>> 1.1.1.{225..244}:/bricks/26 \ >>>>>>> 1.1.1.{185..204}:/bricks/27 \ >>>>>>> 1.1.1.{205..224}:/bricks/27 \ >>>>>>> 1.1.1.{225..244}:/bricks/27 force >>>>>>> >>>>>>> then I mount volume on 50 clients: >>>>>>> mount -t glusterfs 1.1.1.185:/v0 /mnt/gluster >>>>>>> >>>>>>> then I make a directory from one of the clients and chmod it. >>>>>>> mkdir /mnt/gluster/s1 && chmod 777 /mnt/gluster/s1 >>>>>>> >>>>>>> then I start distcp on clients, there are 1059X8.8GB files in one >>>>>>> folder >>>>>>> and >>>>>>> they will be copied to /mnt/gluster/s1 with 100 parallel which means 2 >>>>>>> copy jobs per client at same time. >>>>>>> hadoop distcp -m 100 http://nn1:8020/path/to/teragen-10tb >>>>>>> file:///mnt/gluster/s1 >>>>>>> >>>>>>> After job finished here is the status of s1 directory from bricks: >>>>>>> s1 directory is present in all 1560 brick. >>>>>>> s1/teragen-10tb folder is present in all 1560 brick. >>>>>>> >>>>>>> full listing of files in bricks: >>>>>>> https://www.dropbox.com/s/rbgdxmrtwz8oya8/teragen_list.zip?dl=0 >>>>>>> >>>>>>> You can ignore the .crc files in the brick output above, they are >>>>>>> checksum files... >>>>>>> >>>>>>> As you can see part-m-xxxx files written only some bricks in nodes >>>>>>> 0205..0224 >>>>>>> All bricks have some files but they have zero size. >>>>>>> >>>>>>> I increase file descriptors to 65k so it is not the issue... >>>>>>> >>>>>>> >>>>>>> >>>>>>> >>>>>>> >>>>>>> On Wed, Apr 20, 2016 at 9:34 AM, Xavier Hernandez >>>>>>> <xhernandez at datalab.es> >>>>>>> wrote: >>>>>>>> >>>>>>>> >>>>>>>> >>>>>>>> Hi Serkan, >>>>>>>> >>>>>>>> On 19/04/16 15:16, Serkan ?oban wrote: >>>>>>>>>>>> >>>>>>>>>>>> >>>>>>>>>>>> >>>>>>>>>>>> >>>>>>>>>>>> I assume that gluster is used to store the intermediate files >>>>>>>>>>>> before >>>>>>>>>>>> the reduce phase >>>>>>>>> >>>>>>>>> >>>>>>>>> >>>>>>>>> >>>>>>>>> Nope, gluster is the destination for distcp command. hadoop distcp >>>>>>>>> -m >>>>>>>>> 50 http://nn1:8020/path/to/folder file:///mnt/gluster >>>>>>>>> This run maps on datanodes which have /mnt/gluster mounted on all of >>>>>>>>> them. >>>>>>>> >>>>>>>> >>>>>>>> >>>>>>>> >>>>>>>> >>>>>>>> I don't know hadoop, so I'm of little help here. However it seems >>>>>>>> that >>>>>>>> -m >>>>>>>> 50 >>>>>>>> means to execute 50 copies in parallel. This means that even if the >>>>>>>> distribution worked fine, at most 50 (much probably less) of the 78 >>>>>>>> ec >>>>>>>> sets >>>>>>>> would be used in parallel. >>>>>>>> >>>>>>>>> >>>>>>>>>>>> This means that this is caused by some peculiarity of the >>>>>>>>>>>> mapreduce. >>>>>>>>> >>>>>>>>> >>>>>>>>> >>>>>>>>> >>>>>>>>> Yes but how a client write 500 files to gluster mount and those file >>>>>>>>> just written only to subset of subvolumes? I cannot use gluster as a >>>>>>>>> backup cluster if I cannot write with distcp. >>>>>>>>> >>>>>>>> >>>>>>>> All 500 files were created only on one of the 78 ec sets and the >>>>>>>> remaining >>>>>>>> 77 got empty ? >>>>>>>> >>>>>>>>>>>> You should look which files are created in each brick and how >>>>>>>>>>>> many >>>>>>>>>>>> while the process is running. >>>>>>>>> >>>>>>>>> >>>>>>>>> >>>>>>>>> >>>>>>>>> Files only created on nodes 185..204 or 205..224 or 225..244. Only >>>>>>>>> on >>>>>>>>> 20 nodes in each test. >>>>>>>> >>>>>>>> >>>>>>>> >>>>>>>> >>>>>>>> >>>>>>>> How many files there were in each brick ? >>>>>>>> >>>>>>>> Not sure if this can be related, but standard linux distributions >>>>>>>> have >>>>>>>> a >>>>>>>> default limit of 1024 open file descriptors. Having a so big volume >>>>>>>> and >>>>>>>> doing a massive copy, maybe this limit is affecting something ? >>>>>>>> >>>>>>>> Are there any error or warning messages in the mount or bricks logs ? >>>>>>>> >>>>>>>> >>>>>>>> Xavi >>>>>>>> >>>>>>>>> >>>>>>>>> On Tue, Apr 19, 2016 at 1:05 PM, Xavier Hernandez >>>>>>>>> <xhernandez at datalab.es> >>>>>>>>> wrote: >>>>>>>>>> >>>>>>>>>> >>>>>>>>>> >>>>>>>>>> >>>>>>>>>> Hi Serkan, >>>>>>>>>> >>>>>>>>>> moved to gluster-users since this doesn't belong to devel list. >>>>>>>>>> >>>>>>>>>> On 19/04/16 11:24, Serkan ?oban wrote: >>>>>>>>>>> >>>>>>>>>>> >>>>>>>>>>> >>>>>>>>>>> >>>>>>>>>>> >>>>>>>>>>> I am copying 10.000 files to gluster volume using mapreduce on >>>>>>>>>>> clients. Each map process took one file at a time and copy it to >>>>>>>>>>> gluster volume. >>>>>>>>>> >>>>>>>>>> >>>>>>>>>> >>>>>>>>>> >>>>>>>>>> >>>>>>>>>> >>>>>>>>>> I assume that gluster is used to store the intermediate files >>>>>>>>>> before >>>>>>>>>> the >>>>>>>>>> reduce phase. >>>>>>>>>> >>>>>>>>>>> My disperse volume consist of 78 subvolumes of 16+4 disk each. So >>>>>>>>>>> If >>>>>>>>>>> I >>>>>>>>>>> copy >78 files parallel I expect each file goes to different >>>>>>>>>>> subvolume >>>>>>>>>>> right? >>>>>>>>>> >>>>>>>>>> >>>>>>>>>> >>>>>>>>>> >>>>>>>>>> >>>>>>>>>> >>>>>>>>>> If you only copy 78 files, most probably you will get some >>>>>>>>>> subvolume >>>>>>>>>> empty >>>>>>>>>> and some other with more than one or two files. It's not an exact >>>>>>>>>> distribution, it's a statistially balanced distribution: over time >>>>>>>>>> and >>>>>>>>>> with >>>>>>>>>> enough files, each brick will contain an amount of files in the >>>>>>>>>> same >>>>>>>>>> order >>>>>>>>>> of magnitude, but they won't have the *same* number of files. >>>>>>>>>> >>>>>>>>>>> In my tests during tests with fio I can see every file goes to >>>>>>>>>>> different subvolume, but when I start mapreduce process from >>>>>>>>>>> clients >>>>>>>>>>> only 78/3=26 subvolumes used for writing files. >>>>>>>>>> >>>>>>>>>> >>>>>>>>>> >>>>>>>>>> >>>>>>>>>> >>>>>>>>>> >>>>>>>>>> This means that this is caused by some peculiarity of the >>>>>>>>>> mapreduce. >>>>>>>>>> >>>>>>>>>>> I see that clearly from network traffic. Mapreduce on client side >>>>>>>>>>> can >>>>>>>>>>> be run multi thread. I tested with 1-5-10 threads on each client >>>>>>>>>>> but >>>>>>>>>>> every time only 26 subvolumes used. >>>>>>>>>>> How can I debug the issue further? >>>>>>>>>> >>>>>>>>>> >>>>>>>>>> >>>>>>>>>> >>>>>>>>>> >>>>>>>>>> >>>>>>>>>> You should look which files are created in each brick and how many >>>>>>>>>> while >>>>>>>>>> the >>>>>>>>>> process is running. >>>>>>>>>> >>>>>>>>>> Xavi >>>>>>>>>> >>>>>>>>>> >>>>>>>>>>> >>>>>>>>>>> On Tue, Apr 19, 2016 at 11:22 AM, Xavier Hernandez >>>>>>>>>>> <xhernandez at datalab.es> wrote: >>>>>>>>>>>> >>>>>>>>>>>> >>>>>>>>>>>> >>>>>>>>>>>> >>>>>>>>>>>> >>>>>>>>>>>> Hi Serkan, >>>>>>>>>>>> >>>>>>>>>>>> On 19/04/16 09:18, Serkan ?oban wrote: >>>>>>>>>>>>> >>>>>>>>>>>>> >>>>>>>>>>>>> >>>>>>>>>>>>> >>>>>>>>>>>>> >>>>>>>>>>>>> >>>>>>>>>>>>> Hi, I just reinstalled fresh 3.7.11 and I am seeing the same >>>>>>>>>>>>> behavior. >>>>>>>>>>>>> 50 clients copying part-0-xxxx named files using mapreduce to >>>>>>>>>>>>> gluster >>>>>>>>>>>>> using one thread per server and they are using only 20 servers >>>>>>>>>>>>> out >>>>>>>>>>>>> of >>>>>>>>>>>>> 60. On the other hand fio tests use all the servers. Anything I >>>>>>>>>>>>> can >>>>>>>>>>>>> do >>>>>>>>>>>>> to solve the issue? >>>>>>>>>>>> >>>>>>>>>>>> >>>>>>>>>>>> >>>>>>>>>>>> >>>>>>>>>>>> >>>>>>>>>>>> >>>>>>>>>>>> >>>>>>>>>>>> Distribution of files to ec sets is done by dht. In theory if you >>>>>>>>>>>> create >>>>>>>>>>>> many files each ec set will receive the same amount of files. >>>>>>>>>>>> However >>>>>>>>>>>> when >>>>>>>>>>>> the number of files is small enough, statistics can fail. >>>>>>>>>>>> >>>>>>>>>>>> Not sure what you are doing exactly, but a mapreduce procedure >>>>>>>>>>>> generally >>>>>>>>>>>> only creates a single output. In that case it makes sense that >>>>>>>>>>>> only >>>>>>>>>>>> one >>>>>>>>>>>> ec >>>>>>>>>>>> set is used. If you want to use all ec sets for a single file, >>>>>>>>>>>> you >>>>>>>>>>>> should >>>>>>>>>>>> enable sharding (I haven't tested that) or split the result in >>>>>>>>>>>> multiple >>>>>>>>>>>> files. >>>>>>>>>>>> >>>>>>>>>>>> Xavi >>>>>>>>>>>> >>>>>>>>>>>> >>>>>>>>>>>>> >>>>>>>>>>>>> Thanks, >>>>>>>>>>>>> Serkan >>>>>>>>>>>>> >>>>>>>>>>>>> >>>>>>>>>>>>> ---------- Forwarded message ---------- >>>>>>>>>>>>> From: Serkan ?oban <cobanserkan at gmail.com> >>>>>>>>>>>>> Date: Mon, Apr 18, 2016 at 2:39 PM >>>>>>>>>>>>> Subject: disperse volume file to subvolume mapping >>>>>>>>>>>>> To: Gluster Users <gluster-users at gluster.org> >>>>>>>>>>>>> >>>>>>>>>>>>> >>>>>>>>>>>>> Hi, I have a problem where clients are using only 1/3 of nodes >>>>>>>>>>>>> in >>>>>>>>>>>>> disperse volume for writing. >>>>>>>>>>>>> I am testing from 50 clients using 1 to 10 threads with file >>>>>>>>>>>>> names >>>>>>>>>>>>> part-0-xxxx. >>>>>>>>>>>>> What I see is clients only use 20 nodes for writing. How is the >>>>>>>>>>>>> file >>>>>>>>>>>>> name to sub volume hashing is done? Is this related to file >>>>>>>>>>>>> names >>>>>>>>>>>>> are >>>>>>>>>>>>> similar? >>>>>>>>>>>>> >>>>>>>>>>>>> My cluster is 3.7.10 with 60 nodes each has 26 disks. Disperse >>>>>>>>>>>>> volume >>>>>>>>>>>>> is 78 x (16+4). Only 26 out of 78 sub volumes used during >>>>>>>>>>>>> writes.. >>>>>>>>>>>>> >>>>>>>>>>>> >>>>>>>>>> >>>>>>>> >>>>>> >>>> >>
Serkan Çoban
2016-Apr-21 13:19 UTC
[Gluster-users] disperse volume file to subvolume mapping
Same result. Also checked the rebalance.log file, it has also no reference to part files... On Thu, Apr 21, 2016 at 3:34 PM, Xavier Hernandez <xhernandez at datalab.es> wrote:> Can you try a 'gluster volume rebalance v0 start force' ? > > > On 21/04/16 14:23, Serkan ?oban wrote: >>> >>> Has the rebalance operation finished successfully ? has it skipped any >>> files ? >> >> Yes according to gluster v rebalance status it is completed without any >> errors. >> rebalance status report is like: >> Node Rebalanced files size Scanned >> failures skipped >> 1.1.1.185 158 29GB 1720 >> 0 314 >> 1.1.1.205 93 46.5GB 761 >> 0 95 >> 1.1.1.225 74 37GB 779 >> 0 94 >> >> >> All other hosts has 0 values. >> >> I double check that files with '---------T' attributes are there, >> maybe some of them deleted but I still see them in bricks... >> I am also concerned why part files not distributed to all 60 nodes? >> Rebalance should do that? >> >> On Thu, Apr 21, 2016 at 1:55 PM, Xavier Hernandez <xhernandez at datalab.es> >> wrote: >>> >>> Hi Serkan, >>> >>> On 21/04/16 12:39, Serkan ?oban wrote: >>>> >>>> >>>> I started a gluster v rebalance v0 start command hoping that it will >>>> equally redistribute files across 60 nodes but it did not do that... >>>> why it did not redistribute files? any thoughts? >>> >>> >>> >>> Has the rebalance operation finished successfully ? has it skipped any >>> files >>> ? >>> >>> After a successful rebalance all files with attributes '---------T' >>> should >>> have disappeared. >>> >>> >>>> >>>> On Thu, Apr 21, 2016 at 11:24 AM, Xavier Hernandez >>>> <xhernandez at datalab.es> wrote: >>>>> >>>>> >>>>> Hi Serkan, >>>>> >>>>> On 21/04/16 10:07, Serkan ?oban wrote: >>>>>>> >>>>>>> >>>>>>> >>>>>>> I think the problem is in the temporary name that distcp gives to the >>>>>>> file while it's being copied before renaming it to the real name. Do >>>>>>> you >>>>>>> know what is the structure of this name ? >>>>>> >>>>>> >>>>>> >>>>>> Distcp temporary file name format is: >>>>>> ".distcp.tmp.attempt_1460381790773_0248_m_000001_0" and the same >>>>>> temporary file name used by one map process. For example I see in the >>>>>> logs that one map copies files part-m-00031,part-m-00047,part-m-00063 >>>>>> sequentially and they all use same temporary file name above. So no >>>>>> original file name appears in temporary file name. >>>>> >>>>> >>>>> >>>>> >>>>> This explains the problem. With the default options, DHT sends all >>>>> files >>>>> to >>>>> the subvolume that should store a file named 'distcp.tmp'. >>>>> >>>>> With this temporary name format, little can be done. >>>>> >>>>>> >>>>>> I will check if we can modify distcp behaviour, or we have to write >>>>>> our mapreduce procedures instead of using distcp. >>>>>> >>>>>>> 2. define the option 'extra-hash-regex' to an expression that matches >>>>>>> your temporary file names and returns the same name that will finally >>>>>>> have. >>>>>>> Depending on the differences between original and temporary file >>>>>>> names, >>>>>>> this >>>>>>> option could be useless. >>>>>>> 3. set the option 'rsync-hash-regex' to 'none'. This will prevent the >>>>>>> name conversion, so the files will be evenly distributed. However >>>>>>> this >>>>>>> will >>>>>>> cause a lot of files placed in incorrect subvolumes, creating a lot >>>>>>> of >>>>>>> link >>>>>>> files until a rebalance is executed. >>>>>> >>>>>> >>>>>> >>>>>> >>>>>> How can I set these options? >>>>> >>>>> >>>>> >>>>> >>>>> You can set gluster options using: >>>>> >>>>> gluster volume set <volname> <option> <value> >>>>> >>>>> for example: >>>>> >>>>> gluster volume set v0 rsync-hash-regex none >>>>> >>>>> Xavi >>>>> >>>>> >>>>>> >>>>>> >>>>>> >>>>>> On Thu, Apr 21, 2016 at 10:00 AM, Xavier Hernandez >>>>>> <xhernandez at datalab.es> wrote: >>>>>>> >>>>>>> >>>>>>> >>>>>>> Hi Serkan, >>>>>>> >>>>>>> I think the problem is in the temporary name that distcp gives to the >>>>>>> file >>>>>>> while it's being copied before renaming it to the real name. Do you >>>>>>> know >>>>>>> what is the structure of this name ? >>>>>>> >>>>>>> DHT selects the subvolume (in this case the ec set) on which the file >>>>>>> will >>>>>>> be stored based on the name of the file. This has a problem when a >>>>>>> file >>>>>>> is >>>>>>> being renamed, because this could change the subvolume where the file >>>>>>> should >>>>>>> be found. >>>>>>> >>>>>>> DHT has a feature to avoid incorrect file placements when executing >>>>>>> renames >>>>>>> for the rsync case. What it does is to check if the file matches the >>>>>>> following regular expression: >>>>>>> >>>>>>> ^\.(.+)\.[^.]+$ >>>>>>> >>>>>>> If a match is found, it only considers the part between parenthesis >>>>>>> to >>>>>>> calculate the destination subvolume. >>>>>>> >>>>>>> This is useful for rsync because temporary file names are constructed >>>>>>> in >>>>>>> the >>>>>>> following way: suppose the original filename is 'test'. The temporary >>>>>>> filename while rsync is being executed is made by prepending a dot >>>>>>> and >>>>>>> appending '.<random chars>': .test.712hd >>>>>>> >>>>>>> As you can see, the original name and the part of the name between >>>>>>> parenthesis that matches the regular expression are the same. This >>>>>>> causes >>>>>>> that, after renaming the temporary file to its original filename, >>>>>>> both >>>>>>> files >>>>>>> will be considered to belong to the same subvolume by DHT. >>>>>>> >>>>>>> In your case it's very probable that distcp uses a temporary name >>>>>>> like >>>>>>> '.part.<number>'. In this case the portion of the name used to select >>>>>>> the >>>>>>> subvolume is always 'part'. This would explain why all files go to >>>>>>> the >>>>>>> same >>>>>>> subvolume. Once the file is renamed to another name, DHT realizes >>>>>>> that >>>>>>> it >>>>>>> should go to another subvolume. At this point it creates a link file >>>>>>> (those >>>>>>> files with access rights = '---------T') in the correct subvolume but >>>>>>> it >>>>>>> doesn't move it. As you can see, this kind of files are better >>>>>>> balanced. >>>>>>> >>>>>>> To solve this problem you have three options: >>>>>>> >>>>>>> 1. change the temporary filename used by distcp to correctly match >>>>>>> the >>>>>>> regular expression. I'm not sure if this can be configured, but if >>>>>>> this >>>>>>> is >>>>>>> possible, this is the best option. >>>>>>> >>>>>>> 2. define the option 'extra-hash-regex' to an expression that matches >>>>>>> your >>>>>>> temporary file names and returns the same name that will finally >>>>>>> have. >>>>>>> Depending on the differences between original and temporary file >>>>>>> names, >>>>>>> this >>>>>>> option could be useless. >>>>>>> >>>>>>> 3. set the option 'rsync-hash-regex' to 'none'. This will prevent the >>>>>>> name >>>>>>> conversion, so the files will be evenly distributed. However this >>>>>>> will >>>>>>> cause >>>>>>> a lot of files placed in incorrect subvolumes, creating a lot of link >>>>>>> files >>>>>>> until a rebalance is executed. >>>>>>> >>>>>>> Xavi >>>>>>> >>>>>>> >>>>>>> On 20/04/16 14:13, Serkan ?oban wrote: >>>>>>>> >>>>>>>> >>>>>>>> >>>>>>>> >>>>>>>> Here is the steps that I do in detail and relevant output from >>>>>>>> bricks: >>>>>>>> >>>>>>>> I am using below command for volume creation: >>>>>>>> gluster volume create v0 disperse 20 redundancy 4 \ >>>>>>>> 1.1.1.{185..204}:/bricks/02 \ >>>>>>>> 1.1.1.{205..224}:/bricks/02 \ >>>>>>>> 1.1.1.{225..244}:/bricks/02 \ >>>>>>>> 1.1.1.{185..204}:/bricks/03 \ >>>>>>>> 1.1.1.{205..224}:/bricks/03 \ >>>>>>>> 1.1.1.{225..244}:/bricks/03 \ >>>>>>>> 1.1.1.{185..204}:/bricks/04 \ >>>>>>>> 1.1.1.{205..224}:/bricks/04 \ >>>>>>>> 1.1.1.{225..244}:/bricks/04 \ >>>>>>>> 1.1.1.{185..204}:/bricks/05 \ >>>>>>>> 1.1.1.{205..224}:/bricks/05 \ >>>>>>>> 1.1.1.{225..244}:/bricks/05 \ >>>>>>>> 1.1.1.{185..204}:/bricks/06 \ >>>>>>>> 1.1.1.{205..224}:/bricks/06 \ >>>>>>>> 1.1.1.{225..244}:/bricks/06 \ >>>>>>>> 1.1.1.{185..204}:/bricks/07 \ >>>>>>>> 1.1.1.{205..224}:/bricks/07 \ >>>>>>>> 1.1.1.{225..244}:/bricks/07 \ >>>>>>>> 1.1.1.{185..204}:/bricks/08 \ >>>>>>>> 1.1.1.{205..224}:/bricks/08 \ >>>>>>>> 1.1.1.{225..244}:/bricks/08 \ >>>>>>>> 1.1.1.{185..204}:/bricks/09 \ >>>>>>>> 1.1.1.{205..224}:/bricks/09 \ >>>>>>>> 1.1.1.{225..244}:/bricks/09 \ >>>>>>>> 1.1.1.{185..204}:/bricks/10 \ >>>>>>>> 1.1.1.{205..224}:/bricks/10 \ >>>>>>>> 1.1.1.{225..244}:/bricks/10 \ >>>>>>>> 1.1.1.{185..204}:/bricks/11 \ >>>>>>>> 1.1.1.{205..224}:/bricks/11 \ >>>>>>>> 1.1.1.{225..244}:/bricks/11 \ >>>>>>>> 1.1.1.{185..204}:/bricks/12 \ >>>>>>>> 1.1.1.{205..224}:/bricks/12 \ >>>>>>>> 1.1.1.{225..244}:/bricks/12 \ >>>>>>>> 1.1.1.{185..204}:/bricks/13 \ >>>>>>>> 1.1.1.{205..224}:/bricks/13 \ >>>>>>>> 1.1.1.{225..244}:/bricks/13 \ >>>>>>>> 1.1.1.{185..204}:/bricks/14 \ >>>>>>>> 1.1.1.{205..224}:/bricks/14 \ >>>>>>>> 1.1.1.{225..244}:/bricks/14 \ >>>>>>>> 1.1.1.{185..204}:/bricks/15 \ >>>>>>>> 1.1.1.{205..224}:/bricks/15 \ >>>>>>>> 1.1.1.{225..244}:/bricks/15 \ >>>>>>>> 1.1.1.{185..204}:/bricks/16 \ >>>>>>>> 1.1.1.{205..224}:/bricks/16 \ >>>>>>>> 1.1.1.{225..244}:/bricks/16 \ >>>>>>>> 1.1.1.{185..204}:/bricks/17 \ >>>>>>>> 1.1.1.{205..224}:/bricks/17 \ >>>>>>>> 1.1.1.{225..244}:/bricks/17 \ >>>>>>>> 1.1.1.{185..204}:/bricks/18 \ >>>>>>>> 1.1.1.{205..224}:/bricks/18 \ >>>>>>>> 1.1.1.{225..244}:/bricks/18 \ >>>>>>>> 1.1.1.{185..204}:/bricks/19 \ >>>>>>>> 1.1.1.{205..224}:/bricks/19 \ >>>>>>>> 1.1.1.{225..244}:/bricks/19 \ >>>>>>>> 1.1.1.{185..204}:/bricks/20 \ >>>>>>>> 1.1.1.{205..224}:/bricks/20 \ >>>>>>>> 1.1.1.{225..244}:/bricks/20 \ >>>>>>>> 1.1.1.{185..204}:/bricks/21 \ >>>>>>>> 1.1.1.{205..224}:/bricks/21 \ >>>>>>>> 1.1.1.{225..244}:/bricks/21 \ >>>>>>>> 1.1.1.{185..204}:/bricks/22 \ >>>>>>>> 1.1.1.{205..224}:/bricks/22 \ >>>>>>>> 1.1.1.{225..244}:/bricks/22 \ >>>>>>>> 1.1.1.{185..204}:/bricks/23 \ >>>>>>>> 1.1.1.{205..224}:/bricks/23 \ >>>>>>>> 1.1.1.{225..244}:/bricks/23 \ >>>>>>>> 1.1.1.{185..204}:/bricks/24 \ >>>>>>>> 1.1.1.{205..224}:/bricks/24 \ >>>>>>>> 1.1.1.{225..244}:/bricks/24 \ >>>>>>>> 1.1.1.{185..204}:/bricks/25 \ >>>>>>>> 1.1.1.{205..224}:/bricks/25 \ >>>>>>>> 1.1.1.{225..244}:/bricks/25 \ >>>>>>>> 1.1.1.{185..204}:/bricks/26 \ >>>>>>>> 1.1.1.{205..224}:/bricks/26 \ >>>>>>>> 1.1.1.{225..244}:/bricks/26 \ >>>>>>>> 1.1.1.{185..204}:/bricks/27 \ >>>>>>>> 1.1.1.{205..224}:/bricks/27 \ >>>>>>>> 1.1.1.{225..244}:/bricks/27 force >>>>>>>> >>>>>>>> then I mount volume on 50 clients: >>>>>>>> mount -t glusterfs 1.1.1.185:/v0 /mnt/gluster >>>>>>>> >>>>>>>> then I make a directory from one of the clients and chmod it. >>>>>>>> mkdir /mnt/gluster/s1 && chmod 777 /mnt/gluster/s1 >>>>>>>> >>>>>>>> then I start distcp on clients, there are 1059X8.8GB files in one >>>>>>>> folder >>>>>>>> and >>>>>>>> they will be copied to /mnt/gluster/s1 with 100 parallel which means >>>>>>>> 2 >>>>>>>> copy jobs per client at same time. >>>>>>>> hadoop distcp -m 100 http://nn1:8020/path/to/teragen-10tb >>>>>>>> file:///mnt/gluster/s1 >>>>>>>> >>>>>>>> After job finished here is the status of s1 directory from bricks: >>>>>>>> s1 directory is present in all 1560 brick. >>>>>>>> s1/teragen-10tb folder is present in all 1560 brick. >>>>>>>> >>>>>>>> full listing of files in bricks: >>>>>>>> https://www.dropbox.com/s/rbgdxmrtwz8oya8/teragen_list.zip?dl=0 >>>>>>>> >>>>>>>> You can ignore the .crc files in the brick output above, they are >>>>>>>> checksum files... >>>>>>>> >>>>>>>> As you can see part-m-xxxx files written only some bricks in nodes >>>>>>>> 0205..0224 >>>>>>>> All bricks have some files but they have zero size. >>>>>>>> >>>>>>>> I increase file descriptors to 65k so it is not the issue... >>>>>>>> >>>>>>>> >>>>>>>> >>>>>>>> >>>>>>>> >>>>>>>> On Wed, Apr 20, 2016 at 9:34 AM, Xavier Hernandez >>>>>>>> <xhernandez at datalab.es> >>>>>>>> wrote: >>>>>>>>> >>>>>>>>> >>>>>>>>> >>>>>>>>> >>>>>>>>> Hi Serkan, >>>>>>>>> >>>>>>>>> On 19/04/16 15:16, Serkan ?oban wrote: >>>>>>>>>>>>> >>>>>>>>>>>>> >>>>>>>>>>>>> >>>>>>>>>>>>> >>>>>>>>>>>>> >>>>>>>>>>>>> I assume that gluster is used to store the intermediate files >>>>>>>>>>>>> before >>>>>>>>>>>>> the reduce phase >>>>>>>>>> >>>>>>>>>> >>>>>>>>>> >>>>>>>>>> >>>>>>>>>> >>>>>>>>>> Nope, gluster is the destination for distcp command. hadoop distcp >>>>>>>>>> -m >>>>>>>>>> 50 http://nn1:8020/path/to/folder file:///mnt/gluster >>>>>>>>>> This run maps on datanodes which have /mnt/gluster mounted on all >>>>>>>>>> of >>>>>>>>>> them. >>>>>>>>> >>>>>>>>> >>>>>>>>> >>>>>>>>> >>>>>>>>> >>>>>>>>> >>>>>>>>> I don't know hadoop, so I'm of little help here. However it seems >>>>>>>>> that >>>>>>>>> -m >>>>>>>>> 50 >>>>>>>>> means to execute 50 copies in parallel. This means that even if the >>>>>>>>> distribution worked fine, at most 50 (much probably less) of the 78 >>>>>>>>> ec >>>>>>>>> sets >>>>>>>>> would be used in parallel. >>>>>>>>> >>>>>>>>>> >>>>>>>>>>>>> This means that this is caused by some peculiarity of the >>>>>>>>>>>>> mapreduce. >>>>>>>>>> >>>>>>>>>> >>>>>>>>>> >>>>>>>>>> >>>>>>>>>> >>>>>>>>>> Yes but how a client write 500 files to gluster mount and those >>>>>>>>>> file >>>>>>>>>> just written only to subset of subvolumes? I cannot use gluster as >>>>>>>>>> a >>>>>>>>>> backup cluster if I cannot write with distcp. >>>>>>>>>> >>>>>>>>> >>>>>>>>> All 500 files were created only on one of the 78 ec sets and the >>>>>>>>> remaining >>>>>>>>> 77 got empty ? >>>>>>>>> >>>>>>>>>>>>> You should look which files are created in each brick and how >>>>>>>>>>>>> many >>>>>>>>>>>>> while the process is running. >>>>>>>>>> >>>>>>>>>> >>>>>>>>>> >>>>>>>>>> >>>>>>>>>> >>>>>>>>>> Files only created on nodes 185..204 or 205..224 or 225..244. Only >>>>>>>>>> on >>>>>>>>>> 20 nodes in each test. >>>>>>>>> >>>>>>>>> >>>>>>>>> >>>>>>>>> >>>>>>>>> >>>>>>>>> >>>>>>>>> How many files there were in each brick ? >>>>>>>>> >>>>>>>>> Not sure if this can be related, but standard linux distributions >>>>>>>>> have >>>>>>>>> a >>>>>>>>> default limit of 1024 open file descriptors. Having a so big volume >>>>>>>>> and >>>>>>>>> doing a massive copy, maybe this limit is affecting something ? >>>>>>>>> >>>>>>>>> Are there any error or warning messages in the mount or bricks logs >>>>>>>>> ? >>>>>>>>> >>>>>>>>> >>>>>>>>> Xavi >>>>>>>>> >>>>>>>>>> >>>>>>>>>> On Tue, Apr 19, 2016 at 1:05 PM, Xavier Hernandez >>>>>>>>>> <xhernandez at datalab.es> >>>>>>>>>> wrote: >>>>>>>>>>> >>>>>>>>>>> >>>>>>>>>>> >>>>>>>>>>> >>>>>>>>>>> >>>>>>>>>>> Hi Serkan, >>>>>>>>>>> >>>>>>>>>>> moved to gluster-users since this doesn't belong to devel list. >>>>>>>>>>> >>>>>>>>>>> On 19/04/16 11:24, Serkan ?oban wrote: >>>>>>>>>>>> >>>>>>>>>>>> >>>>>>>>>>>> >>>>>>>>>>>> >>>>>>>>>>>> >>>>>>>>>>>> >>>>>>>>>>>> I am copying 10.000 files to gluster volume using mapreduce on >>>>>>>>>>>> clients. Each map process took one file at a time and copy it to >>>>>>>>>>>> gluster volume. >>>>>>>>>>> >>>>>>>>>>> >>>>>>>>>>> >>>>>>>>>>> >>>>>>>>>>> >>>>>>>>>>> >>>>>>>>>>> >>>>>>>>>>> I assume that gluster is used to store the intermediate files >>>>>>>>>>> before >>>>>>>>>>> the >>>>>>>>>>> reduce phase. >>>>>>>>>>> >>>>>>>>>>>> My disperse volume consist of 78 subvolumes of 16+4 disk each. >>>>>>>>>>>> So >>>>>>>>>>>> If >>>>>>>>>>>> I >>>>>>>>>>>> copy >78 files parallel I expect each file goes to different >>>>>>>>>>>> subvolume >>>>>>>>>>>> right? >>>>>>>>>>> >>>>>>>>>>> >>>>>>>>>>> >>>>>>>>>>> >>>>>>>>>>> >>>>>>>>>>> >>>>>>>>>>> >>>>>>>>>>> If you only copy 78 files, most probably you will get some >>>>>>>>>>> subvolume >>>>>>>>>>> empty >>>>>>>>>>> and some other with more than one or two files. It's not an exact >>>>>>>>>>> distribution, it's a statistially balanced distribution: over >>>>>>>>>>> time >>>>>>>>>>> and >>>>>>>>>>> with >>>>>>>>>>> enough files, each brick will contain an amount of files in the >>>>>>>>>>> same >>>>>>>>>>> order >>>>>>>>>>> of magnitude, but they won't have the *same* number of files. >>>>>>>>>>> >>>>>>>>>>>> In my tests during tests with fio I can see every file goes to >>>>>>>>>>>> different subvolume, but when I start mapreduce process from >>>>>>>>>>>> clients >>>>>>>>>>>> only 78/3=26 subvolumes used for writing files. >>>>>>>>>>> >>>>>>>>>>> >>>>>>>>>>> >>>>>>>>>>> >>>>>>>>>>> >>>>>>>>>>> >>>>>>>>>>> >>>>>>>>>>> This means that this is caused by some peculiarity of the >>>>>>>>>>> mapreduce. >>>>>>>>>>> >>>>>>>>>>>> I see that clearly from network traffic. Mapreduce on client >>>>>>>>>>>> side >>>>>>>>>>>> can >>>>>>>>>>>> be run multi thread. I tested with 1-5-10 threads on each client >>>>>>>>>>>> but >>>>>>>>>>>> every time only 26 subvolumes used. >>>>>>>>>>>> How can I debug the issue further? >>>>>>>>>>> >>>>>>>>>>> >>>>>>>>>>> >>>>>>>>>>> >>>>>>>>>>> >>>>>>>>>>> >>>>>>>>>>> >>>>>>>>>>> You should look which files are created in each brick and how >>>>>>>>>>> many >>>>>>>>>>> while >>>>>>>>>>> the >>>>>>>>>>> process is running. >>>>>>>>>>> >>>>>>>>>>> Xavi >>>>>>>>>>> >>>>>>>>>>> >>>>>>>>>>>> >>>>>>>>>>>> On Tue, Apr 19, 2016 at 11:22 AM, Xavier Hernandez >>>>>>>>>>>> <xhernandez at datalab.es> wrote: >>>>>>>>>>>>> >>>>>>>>>>>>> >>>>>>>>>>>>> >>>>>>>>>>>>> >>>>>>>>>>>>> >>>>>>>>>>>>> >>>>>>>>>>>>> Hi Serkan, >>>>>>>>>>>>> >>>>>>>>>>>>> On 19/04/16 09:18, Serkan ?oban wrote: >>>>>>>>>>>>>> >>>>>>>>>>>>>> >>>>>>>>>>>>>> >>>>>>>>>>>>>> >>>>>>>>>>>>>> >>>>>>>>>>>>>> >>>>>>>>>>>>>> >>>>>>>>>>>>>> Hi, I just reinstalled fresh 3.7.11 and I am seeing the same >>>>>>>>>>>>>> behavior. >>>>>>>>>>>>>> 50 clients copying part-0-xxxx named files using mapreduce to >>>>>>>>>>>>>> gluster >>>>>>>>>>>>>> using one thread per server and they are using only 20 servers >>>>>>>>>>>>>> out >>>>>>>>>>>>>> of >>>>>>>>>>>>>> 60. On the other hand fio tests use all the servers. Anything >>>>>>>>>>>>>> I >>>>>>>>>>>>>> can >>>>>>>>>>>>>> do >>>>>>>>>>>>>> to solve the issue? >>>>>>>>>>>>> >>>>>>>>>>>>> >>>>>>>>>>>>> >>>>>>>>>>>>> >>>>>>>>>>>>> >>>>>>>>>>>>> >>>>>>>>>>>>> >>>>>>>>>>>>> >>>>>>>>>>>>> Distribution of files to ec sets is done by dht. In theory if >>>>>>>>>>>>> you >>>>>>>>>>>>> create >>>>>>>>>>>>> many files each ec set will receive the same amount of files. >>>>>>>>>>>>> However >>>>>>>>>>>>> when >>>>>>>>>>>>> the number of files is small enough, statistics can fail. >>>>>>>>>>>>> >>>>>>>>>>>>> Not sure what you are doing exactly, but a mapreduce procedure >>>>>>>>>>>>> generally >>>>>>>>>>>>> only creates a single output. In that case it makes sense that >>>>>>>>>>>>> only >>>>>>>>>>>>> one >>>>>>>>>>>>> ec >>>>>>>>>>>>> set is used. If you want to use all ec sets for a single file, >>>>>>>>>>>>> you >>>>>>>>>>>>> should >>>>>>>>>>>>> enable sharding (I haven't tested that) or split the result in >>>>>>>>>>>>> multiple >>>>>>>>>>>>> files. >>>>>>>>>>>>> >>>>>>>>>>>>> Xavi >>>>>>>>>>>>> >>>>>>>>>>>>> >>>>>>>>>>>>>> >>>>>>>>>>>>>> Thanks, >>>>>>>>>>>>>> Serkan >>>>>>>>>>>>>> >>>>>>>>>>>>>> >>>>>>>>>>>>>> ---------- Forwarded message ---------- >>>>>>>>>>>>>> From: Serkan ?oban <cobanserkan at gmail.com> >>>>>>>>>>>>>> Date: Mon, Apr 18, 2016 at 2:39 PM >>>>>>>>>>>>>> Subject: disperse volume file to subvolume mapping >>>>>>>>>>>>>> To: Gluster Users <gluster-users at gluster.org> >>>>>>>>>>>>>> >>>>>>>>>>>>>> >>>>>>>>>>>>>> Hi, I have a problem where clients are using only 1/3 of nodes >>>>>>>>>>>>>> in >>>>>>>>>>>>>> disperse volume for writing. >>>>>>>>>>>>>> I am testing from 50 clients using 1 to 10 threads with file >>>>>>>>>>>>>> names >>>>>>>>>>>>>> part-0-xxxx. >>>>>>>>>>>>>> What I see is clients only use 20 nodes for writing. How is >>>>>>>>>>>>>> the >>>>>>>>>>>>>> file >>>>>>>>>>>>>> name to sub volume hashing is done? Is this related to file >>>>>>>>>>>>>> names >>>>>>>>>>>>>> are >>>>>>>>>>>>>> similar? >>>>>>>>>>>>>> >>>>>>>>>>>>>> My cluster is 3.7.10 with 60 nodes each has 26 disks. Disperse >>>>>>>>>>>>>> volume >>>>>>>>>>>>>> is 78 x (16+4). Only 26 out of 78 sub volumes used during >>>>>>>>>>>>>> writes.. >>>>>>>>>>>>>> >>>>>>>>>>>>> >>>>>>>>>>> >>>>>>>>> >>>>>>> >>>>> >>> >