[Gluster-users] Slow write times to gluster disk

Pranith Kumar Karampuri
2017-05-10T16:15:44Z

Okay good. At least this validates my doubts. Handling O_SYNC in gluster
NFS and fuse is a bit different.
When application opens a file with O_SYNC on fuse mount then each write
syscall has to be written to disk as part of the syscall where as in case
of NFS, there is no concept of open. NFS performs write though a handle
saying it needs to be a synchronous write, so write() syscall is performed
first then it performs fsync(). so an write on an fd with O_SYNC becomes
write+fsync. I am suspecting that when multiple threads do this
write+fsync() operation on the same file, multiple writes are batched
together to be written do disk so the throughput on the disk is increasing
is my guess.

Does it answer your doubts?

On Wed, May 10, 2017 at 9:35 PM, Pat Haley <phaley at mit.edu> wrote:

>
> Without the oflag=sync and only a single test of each, the FUSE is going
> faster than NFS:
>
> FUSE:
> mseas-data2(dri_nascar)% dd if=/dev/zero count=4096 bs=1048576
> of=zeros.txt conv=sync
> 4096+0 records in
> 4096+0 records out
> 4294967296 bytes (4.3 GB) copied, 7.46961 s, 575 MB/s
>
>
> NFS
> mseas-data2(HYCOM)% dd if=/dev/zero count=4096 bs=1048576 of=zeros.txt
> conv=sync
> 4096+0 records in
> 4096+0 records out
> 4294967296 bytes (4.3 GB) copied, 11.4264 s, 376 MB/s
>
>
>
> On 05/10/2017 11:53 AM, Pranith Kumar Karampuri wrote:
>
> Could you let me know the speed without oflag=sync on both the mounts? No
> need to collect profiles.
>
> On Wed, May 10, 2017 at 9:17 PM, Pat Haley <phaley at mit.edu> wrote:
>
>>
>> Here is what I see now:
>>
>> [root at mseas-data2 ~]# gluster volume info
>>
>> Volume Name: data-volume
>> Type: Distribute
>> Volume ID: c162161e-2a2d-4dac-b015-f31fd89ceb18
>> Status: Started
>> Number of Bricks: 2
>> Transport-type: tcp
>> Bricks:
>> Brick1: mseas-data2:/mnt/brick1
>> Brick2: mseas-data2:/mnt/brick2
>> Options Reconfigured:
>> diagnostics.count-fop-hits: on
>> diagnostics.latency-measurement: on
>> nfs.exports-auth-enable: on
>> diagnostics.brick-sys-log-level: WARNING
>> performance.readdir-ahead: on
>> nfs.disable: on
>> nfs.export-volumes: off
>>
>>
>>
>> On 05/10/2017 11:44 AM, Pranith Kumar Karampuri wrote:
>>
>> Is this the volume info you have?
>>
>> >*     [root at mseas-data2
<http://www.gluster.org/mailman/listinfo/gluster-users> ~]# gluster volume
info
>> *>>*     Volume Name: data-volume
>> *>*     Type: Distribute
>> *>*     Volume ID: c162161e-2a2d-4dac-b015-f31fd89ceb18
>> *>*     Status: Started
>> *>*     Number of Bricks: 2
>> *>*     Transport-type: tcp
>> *>*     Bricks:
>> *>*     Brick1: mseas-data2:/mnt/brick1
>> *>*     Brick2: mseas-data2:/mnt/brick2
>> *>*     Options Reconfigured:
>> *>*     performance.readdir-ahead: on
>> *>*     nfs.disable: on
>> *>*     nfs.export-volumes: off
>>
>> *
>>
>> ?I copied this from old thread from 2016. This is distribute volume.
Did
>> you change any of the options in between?
>>
>> --
>>
>> -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
>> Pat Haley                          Email:  phaley at mit.edu
>> Center for Ocean Engineering       Phone:  (617) 253-6824
>> Dept. of Mechanical Engineering    Fax:    (617) 253-8125
>> MIT, Room 5-213                    http://web.mit.edu/phaley/www/
>> 77 Massachusetts Avenue
>> Cambridge, MA  02139-4301
>>
>> --
> Pranith
>
> --
>
> -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
> Pat Haley                          Email:  phaley at mit.edu
> Center for Ocean Engineering       Phone:  (617) 253-6824
> Dept. of Mechanical Engineering    Fax:    (617) 253-8125
> MIT, Room 5-213                    http://web.mit.edu/phaley/www/
> 77 Massachusetts Avenue
> Cambridge, MA  02139-4301
>
>


--
Pranith
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