3 ms·

SuSE/OpenSuSE has been using BTRFS by default for a while and it seems to work well enough. There's a default schedule of running 'btrfs balance' every week, s

SuSE/OpenSuSE has been using BTRFS by default for a while and it seems to work well enough. There's a default schedule of running 'btrfs balance' every week, seemingly based on when the OS was installed (it relies on the timestamp of a file that gets updated with every run), that makes the system(1) virtually unusable for about 15 minutes. (1) I've only seen this on one machine, so maybe it's a quirk of that machine's workload. But it sure does suck when it's in the middle of a workday.

codys 9y ago
On btrfs causing latency: I've got a few systems with btrfs as the rootfs (on top of lvm, on top of dm-crypt, on a SSD). I recently started using `snapper` to create snapshots on a schedule on them. I enabled quota support in btrfs so I could see how much space snapshots were using. I noticed that filesystem wide latency tended to spike when removing snapshots (several minutes of all fs access stalling). Balancing with quotas enabled is even worse: my systems were hung for multiple days, until I forcibly restarted them and disabled quotas. Then the fs hangs were much smaller (a few seconds) and not to noticeable. Balancing finished in something on the order of an hour. While I had quotas enabled, I was constantly having btrfs tell me the data was bad and needed rescanning (rescanning quotas would also induce fs wide latency). The thing is, ZFS has snapshot space usage info, and doesn't have awful latency (it also doesn't have a "balance" operation, but I'm not sure how relevant that is). Given my experience with both btrfs & ZFS, I'll likely consider using ZFS as my rootfs in the future.
- Mister_Snuggles 9y ago
  I have no idea what the state of ZFS on Linux is, but I've been using it on FreeBSD for a while now and it's fantastic. Comparing FreeBSD to Linux is a bit of an apples/oranges thing though.
cyphar 9y ago
Yeah, that happens to me too. I believe the reason why the lag is so bad on openSUSE / SUSE [aside: note the spelling :P] is because we carry patches that make quotas actually apply correctly (but it increases the big-O complexity by quite a lot -- making balances way more expensive).
krylon 9y ago
I've seen it, too. I have three machines running openSUSE, and the one I've seen it on is both the least powerful one (Lenovo IdeaPad 100, some Atom chip, 2GB RAM) and the only one with a non-SSD drive.

codys 9y ago

On btrfs causing latency: I've got a few systems with btrfs as the rootfs (on top of lvm, on top of dm-crypt, on a SSD). I recently started using `snapper` to create snapshots on a schedule on them. I enabled quota support in btrfs so I could see how much space snapshots were using. I noticed that filesystem wide latency tended to spike when removing snapshots (several minutes of all fs access stalling). Balancing with quotas enabled is even worse: my systems were hung for multiple days, until I forcibly restarted them and disabled quotas. Then the fs hangs were much smaller (a few seconds) and not to noticeable. Balancing finished in something on the order of an hour. While I had quotas enabled, I was constantly having btrfs tell me the data was bad and needed rescanning (rescanning quotas would also induce fs wide latency). The thing is, ZFS has snapshot space usage info, and doesn't have awful latency (it also doesn't have a "balance" operation, but I'm not sure how relevant that is). Given my experience with both btrfs & ZFS, I'll likely consider using ZFS as my rootfs in the future.

Mister_Snuggles 9y ago
I have no idea what the state of ZFS on Linux is, but I've been using it on FreeBSD for a while now and it's fantastic. Comparing FreeBSD to Linux is a bit of an apples/oranges thing though.

cyphar 9y ago

Yeah, that happens to me too. I believe the reason why the lag is so bad on openSUSE / SUSE [aside: note the spelling :P] is because we carry patches that make quotas actually apply correctly (but it increases the big-O complexity by quite a lot -- making balances way more expensive).

krylon 9y ago

I've seen it, too. I have three machines running openSUSE, and the one I've seen it on is both the least powerful one (Lenovo IdeaPad 100, some Atom chip, 2GB RAM) and the only one with a non-SSD drive.