I don't know if you eventually found an answer yourself, but since nobody else has replied, here's what I found:
Am Tue, 17 Jun 2014 13:04:08 +0200 schrieb "Stefan G. Weichinger" <[email protected]>: > > ... I am quite happy now with the performance of that new server I am > preparing. > > See thread "Intel(R) C600 SAS Controller" for that story: > > https://www.mail-archive.com/[email protected]/msg146119.html > > Right now I get quite good results when doing backups of the 2 existing > VMs (which have their virtio-disks on LVM-LVs on the host) ... up to > 200MB/s ... I can show for reference, if someone is interested. > > I think that is around the possible maximum. > > ---> > > The issue I want to share with you is related to a btrfs subvol I have here. > > Block device sda builds the btrfs-pool containing the root-fs: > > # btrfs fi show > Label: ROOT uuid: 9133c469-df1e-45f5-a09f-d1b9c75c69da > Total devices 1 FS bytes used 29.47GiB > devid 1 size 500.00GiB used 278.04GiB path /dev/sda > > Btrfs v3.12 > > These are the subvolumes (I could/should rm some, but it doesn't matter > for this issue, afaik): > > # btrfs su list / > ID 257 gen 4282 top level 5 path __active > ID 258 gen 4874 top level 5 path __active/root > ID 266 gen 4772 top level 258 path images > ID 267 gen 838 top level 258 path images/otrs > ID 289 gen 4285 top level 258 path images/windows > ID 538 gen 4874 top level 5 path __active/virt-backup > > > fstab has: > > # grep btrfs /etc/fstab > LABEL=ROOT / btrfs defaults,noatime,compress=lzo 0 0 > LABEL=ROOT /mnt/virt-backup btrfs > compress=no,noatime,subvolid=538 0 0 > > > ... so I want to mount subvolid 538 with disabled compression (to speed > up backups as the files written to it are compressed on the fly via pigz > already). So far nothing in particular stands out, that is, it looks like everything is correct. > But after booting I get that dir mounted with compress=lzo (which is > default). > > # mount | grep btrfs > /dev/sda on / type btrfs (rw,noatime,compress=lzo,space_cache) > /dev/sda on /mnt/virt-backup type btrfs > (rw,noatime,compress=lzo,space_cache) > > remounting works, though: > > booze ~ # mount -o remount,compress=no /mnt/virt-backup/ > > booze ~ # mount | grep btrfs > /dev/sda on / type btrfs (rw,noatime,space_cache) > /dev/sda on /mnt/virt-backup type btrfs (rw,noatime,space_cache) > > BUT it remounts / without compression as well ... ! > > Is it a bug? A mistake or misunderstanding? From my own google search, at least up to 2011 per-subvolume compression settings were not possible. Then, after subsequently searching on the btrfs wiki for a while, I finally found an answer: no. See this FAQ entry: https://btrfs.wiki.kernel.org/index.php/FAQ#Can_I_mount_subvolumes_with_different_mount_options.3F [...] HTH -- Marc Joliet -- "People who think they know everything really annoy those of us who know we don't" - Bjarne Stroustrup
signature.asc
Description: PGP signature
