On Mon, Oct 07, 2013 at 01:45:29PM +0200, Laurent Humblet wrote: > I have added 2x2Tb to my existing 2x2Tb raid 1 btrfs filesystem and > then ran a balance: > > # btrfs filesystem show > Total devices 4 FS bytes used 1.74TB > devid 3 size 1.82TB used 0.00 path /dev/sdd > devid 4 size 1.82TB used 0.00 path /dev/sde > devid 2 size 1.82TB used 1.75TB path /dev/sdc > devid 1 size 1.82TB used 1.75TB path /dev/sdb > # btrfs filesystem balance btrfs_root/ > # btrfs filesystem show > Total devices 4 FS bytes used 1.74TB > devid 3 size 1.82TB used 892.00GB path /dev/sdd > devid 4 size 1.82TB used 892.00GB path /dev/sde > devid 2 size 1.82TB used 891.03GB path /dev/sdc > devid 1 size 1.82TB used 891.04GB path /dev/sdb > > It took 59 hours to complete the balance. > > I checked on a couple of files and all seems fine but I have some questions: > - is there some kind of 'overall filesystem health/integrity check' > that I should do on the filesystem now that the balance is done? See btrfs scrub start > - also, I ran the command while some of the btrfs subvolumes were > mounted (as well as the btrfs_root/ of course), does this impact on > the balance job? No. > - the mounted btrfs devices were mounted using -o > space_cache,inode_cache but the btrfs_root/ was not, also, does this > impact on the balance job? No. > - about those options, a few months ago, I oftent had > btrfs-cache-1/btrfs-endio-met processes taking some cpu/hd time. I > was advised to mount -o space_cache,inode_cache, which seems to have > quiet the processes down. Are those options still necessary now? No, once you've mounted with them once (and had the caches rebuilt) they're not necessary to use any more. > - as the job took 60+ hours but the CPU rarely went above 10%, the > computer seemed still usable. I left it do its job of course but > could I have accessed or write anything on the subvolumes while the > balance was running and if yes, would this have any impact on the > filesystem? Absolutely, yes, you could have done. It would probably be slower than normal to access the files while the balance is happening, because the balance is using up I/O bandwidth, but other than that there should be no impact. Hugo. -- === Hugo Mills: hugo@... carfax.org.uk | darksatanic.net | lug.org.uk === PGP key: 65E74AC0 from wwwkeys.eu.pgp.net or http://www.carfax.org.uk --- argc, argv, argh! ---
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