4 ms·

Until the BTRS filesystem gets to some indeterminate threshold of “almost full”, at which point you typically need to reformat and restore from backups…

wtallis 3y ago
I haven't been following BTRFS development closely for a few years, so I don't know how much more progress they've made on eliminating those corner cases. But I'm still careful about not letting the filesystem get close to full. Earlier this month, I noticed one of my machines was over 80% full, so I grabbed a few drives I had lying around that weren't in use at the time and added them to the array. The flexibility of BTRFS gives you a lot more options than eg. ZFS for getting out of a tight spot without the full wipe and restore hassle. But both can still leave you stuck, especially if you ignore the need for monitoring and preventive maintenance.
- tatersolid 3y ago
  Disk full is not a “corner case”. It should be one of the first test cases a filesystem test suite should have, and that test should always pass in every configuration. The fact that total data loss happened regularly on full volumes many years after a “stable” release means BTRFS is either fundamentally flawed in design or incompetently implemented. I have no idea how it was accepted into mainline Linux. The fact that a certain large NAS vendor used BTRFS by default (without documentation at the time of purchase) has cost my org and others lots of downtime and money.
  - wtallis 3y ago
    > Disk full is not a “corner case”. I didn't say it was. There are plenty of disk full scenarios that can be handled by BTRFS without trouble, especially when adding more disks (even temporarily) is an option. There are ways to get stuck with a full fs, but it's not a guarantee you'll end up in a "wipe and restore from backup" situation. (And to be fair, ZFS also gets very problematic when completely full; this is a general problem for CoW filesystems.)
- ilyt 3y ago
  Sooo basically if you were using XFS you wouldn't need to do anything at all till it got 99% full, and if you got it there you'd just get "disk is full" message instead of some catastrophe? I don't need that kind of stress in my life... And with plain RAID6 I can still add hard drives if needed. Yeah the case of buying bigger drives is still a bit iffy but btrfs RAID1 gonna lose me more space than RAID6+LVM+xfs anyway...

wtallis 3y ago

I haven't been following BTRFS development closely for a few years, so I don't know how much more progress they've made on eliminating those corner cases. But I'm still careful about not letting the filesystem get close to full. Earlier this month, I noticed one of my machines was over 80% full, so I grabbed a few drives I had lying around that weren't in use at the time and added them to the array. The flexibility of BTRFS gives you a lot more options than eg. ZFS for getting out of a tight spot without the full wipe and restore hassle. But both can still leave you stuck, especially if you ignore the need for monitoring and preventive maintenance.

tatersolid 3y ago
Disk full is not a “corner case”. It should be one of the first test cases a filesystem test suite should have, and that test should always pass in every configuration. The fact that total data loss happened regularly on full volumes many years after a “stable” release means BTRFS is either fundamentally flawed in design or incompetently implemented. I have no idea how it was accepted into mainline Linux. The fact that a certain large NAS vendor used BTRFS by default (without documentation at the time of purchase) has cost my org and others lots of downtime and money.
- wtallis 3y ago
  > Disk full is not a “corner case”. I didn't say it was. There are plenty of disk full scenarios that can be handled by BTRFS without trouble, especially when adding more disks (even temporarily) is an option. There are ways to get stuck with a full fs, but it's not a guarantee you'll end up in a "wipe and restore from backup" situation. (And to be fair, ZFS also gets very problematic when completely full; this is a general problem for CoW filesystems.)
ilyt 3y ago
Sooo basically if you were using XFS you wouldn't need to do anything at all till it got 99% full, and if you got it there you'd just get "disk is full" message instead of some catastrophe? I don't need that kind of stress in my life... And with plain RAID6 I can still add hard drives if needed. Yeah the case of buying bigger drives is still a bit iffy but btrfs RAID1 gonna lose me more space than RAID6+LVM+xfs anyway...