My understanding is that “replace-brick” is deprecated http://www.gluster.org/pipermail/gluster-users/2012-October/034473.html And that the “add-brick” followed by “remove-brick” should behave the same way. It does not behave as predicted, I think, because my system is unbalanced. I have no idea whether or no the “replace-brick” command will behave differently. Andy On Apr 11, 2014, at 5:34 PM, Machiel Groeneveld <machielg@xxxxxxxxx> wrote: > Isn't that what replace-brick is for? > > >> On 11 Apr 2014, at 23:32, Andrew Smith <smith.andrew.james@xxxxxxxxx> wrote: >> >> >> Hi, I have a problem, which I hope for your sake, is uncommon. >> >> I built a Gluster volume with 8 bricks, 4 80TB and 4 68TB with >> a total capacity of about 600TB. The underlying filesystem >> is BTRFS. >> >> I found out after the system was half full that BTRFS was a >> bad idea. BTRFS doesn’t have inodes. It allocates some fraction >> of the disk space to metadata and when it runs out, it allocates >> more. This allocation process on large volumes is painfully slow >> and brings effective write speeds down to only a few MB/s with long >> timeouts. The data can be read at high speeds, but writing to the >> volume is a big fat mess. Reading is still fairly fast though, >> so access to the my data by users is acceptable. >> >> I need to keep this volume available and I don’t have a second >> copy of the hardware to rebuild the system on. So, I need to do >> an in-situ transition from BTRFS to XFS. >> >> To do this, I first cleared out some data to free up metadata space, >> and then with much difficulty managed to do a >> >> # gluster volume remove-brick >> >> I retired the removed brick and then reformatted it with XFS and added >> it back to my Gluster volume. At this point, I thought I was nearly >> home. I thought I could retire a second brick and the data would >> be copied to the empty brick. However, this is not what happens. >> Some data ends up on the newly added brick, but some of the data >> flows elsewhere, which due to the BTRFS problem is a nightmare. >> >> I assume this is because when I took my volume from 8 bricks to 7, it >> became unbalanced. The data on the brick that I was retiring >> belongs on several different bricks and so I am not just doing a >> substitution. >> >> I need to be able to tell my Gluster volume to include all the bricks, >> but do not write files to any of the BTRFS bricks so that it puts data >> only on the XFS brick. If I could somehow tell Gluster that these bricks >> were full, that would suffice. >> >> I could do a "rebalance migrate-data" to make make the data on the BTRFS >> volumes more uniform, but I don’t know how this will work. Does reposition >> the data brick by brick or file by file. Brick by brick would be bad, since >> the last brick to rebalance would need to receive all the data that it requires >> before it would get to write data out to free up metadata space. >> >> There is a “rebalance-brick” option in the man page, but I don’t see that >> documented. This may be useful, but I have no idea what it will do. >> >> Is there a solution to my problem? Whip it and start over is not helpful. >> Any help on how I can predict where data will go will also help. >> >> Andy >> _______________________________________________ >> Gluster-users mailing list >> Gluster-users@xxxxxxxxxxx >> http://supercolony.gluster.org/mailman/listinfo/gluster-users _______________________________________________ Gluster-users mailing list Gluster-users@xxxxxxxxxxx http://supercolony.gluster.org/mailman/listinfo/gluster-users
