Subject: Re: Recommended why to use btrfs for production?
Date: Friday 3rd June 2016 12:55:18 UTC (about 1 year ago)
On 2016-06-03 05:49, Martin wrote: > Hello, > > We would like to use urBackup to make laptop backups, and they mention > btrfs as an option. > > https://www.urbackup.org/administration_manual.html#x1-8400010.6 > > So if we go with btrfs and we need 100TB usable space in raid6, and to > have it replicated each night to another btrfs server for "backup" of > the backup, how should we then install btrfs? > > E.g. Should we use the latest Fedora, CentOS, Ubuntu, Ubuntu LTS, or > should we compile the kernel our self? In general, avoid Ubuntu LTS versions when dealing with BTRFS, as well as most enterprise distros, they all tend to back-port patches instead of using newer kernels, which means it's functionally impossible to provide good support for them here (because we can't know for sure what exactly they've back-ported). I'd suggest building your own kernel if possible, with Arch Linux being a close second (they follow upstream very closely), followed by Fedora and non-LTS Ubuntu. > > And a bonus question: How stable is raid6 and detecting and replacing > failed drives? Do not use BTRFS raid6 mode in production, it has at least 2 known serious bugs that may cause complete loss of the array due to a disk failure. Both of these issues have as of yet unknown trigger conditions, although they do seem to occur more frequently with larger arrays. That said, there are other options. If you have enough disks, you can run BTRFS raid1 on top of LVM or MD RAID5 or RAID6, which provides you with the benefits of both. Alternatively, you could use BTRFS raid1 on top of LVM or MD RAID1, which actually gets relatively decent performance and can provide even better guarantees than RAID6 would (depending on how you set it up, you can lose a lot more disks safely). If you go this way, I'd suggest setting up disks in pairs at the lower level, and then just let BTRFS handle spanning the data across disks (BTRFS raid1 mode keeps exactly two copies of each block). While this is not quite as efficient as just doing LVM based RAID6 with a traditional FS on top, it's also a lot easier to handle reshaping the array on-line because of the device management in BTRFS itself. -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html