Hi Markus, You are right .I think that the 3 node setup matches distributed volume. According to https://docs.gluster.org/en/latest/Administrator%20Guide/Setting%20Up%20Volumes/ Dispersed volumes use erasure codes to have a 'parity' on a separate brick. In such case you can afford to loose a brick without loosing data and you will need more bricks. Yet, I don't see anything about RAID6 being required. Use the gluster's official documentation (if possible) as it is the most recent info. Maybe you can share the ammount of disks , raid controllers and servers you have and your tolerance to data loss. Then I can share my thoughts on the possible volume types. Best Regards, Strahil Nikolov On Jan 14, 2020 20:33, Markus Kern <gluster at military.de> wrote:> > Hi Strahil, > > thanks for you answer - but now I am completely lost :) > > From this documentation: > https://docs.oracle.com/cd/E52668_01/F10040/html/gluster-312-volume-distr-disp.html > > "As a dispersed volume must have a minimum of three bricks, a > distributed dispersed volume must have at least six bricks. For example, > six nodes with one brick, or three nodes with two bricks on each node > are needed for this volume type." > > So for a distributed dispersed volume I need at least six bricks. If > each brick is a RAID6, I have 6 x 2 Parity disks = 12 disks for parity. > > In your example you only have one brick per node in a three node setup. > This is no distributed dispersed volume then, right? > > A confused Markus > > > Am 14.01.2020 16:29, schrieb Strahil: > > Hi Markus, > > > > Distributed dispersed volume is just LVM's linear LV -> so in case of > > brick failiure - you loose the data on it. > > > > Raid 6 requires? 2 disks? for parity, so you can make a large RAID6 > > and use that as a single brick - so the disks that hold? the parity > > data are? only 6 ( 3 nodes x 2 disks). > > > > Of course? if you have too many disks? for a single raid controller > > ,that you can consider a? replica volume? with an arbiter. > > > > > > Best Regards, > > Strahil Nikolov > > > > On Jan 14, 2020 13:36, Markus Kern <gluster at military.de> wrote: > >> > >> > >> Greetings again! > >> > >> After reading RedHat documentation regarding optimizing Gluster > >> storage > >> another question comes to my mind: > >> > >> Let's presume that I want to go the distributed dispersed volume way. > >> Three nodes which two bricks each. > >> According to RedHat's recommendation, I should use RAID6 as underlying > >> RAID for my planned workload. > >> I am frightened by that "waste" of disks in such a case: > >> When each brick is a RAID6, I would "loose" two disks per brick - 12 > >> lossed disks in total. > >> In addition to this, distributed dispersed volume adds another layer > >> of > >> lossed disk space. > >> > >> Am I wrong here? Maybe I didn't understand the recommendations wrong? > >> > >> Markus > >> ________ > >> > >> Community Meeting Calendar: > >> > >> APAC Schedule - > >> Every 2nd and 4th Tuesday at 11:30 AM IST > >> Bridge: https://bluejeans.com/441850968 > >> > >> NA/EMEA Schedule - > >> Every 1st and 3rd Tuesday at 01:00 PM EDT > >> Bridge: https://bluejeans.com/441850968 > >> > >> Gluster-users mailing list > >> Gluster-users at gluster.org > >> https://lists.gluster.org/mailman/listinfo/gluster-users