> On 10 Jan 2017, at 21:07, Vinko Magecic <vinko.mage...@construction.com> > wrote: > > Hello, > > I set up a raid 1 with two btrfs devices and came across some situations in > my testing that I can't get a straight answer on. > 1) When replacing a volume, do I still need to `umount /path` and then `mount > -o degraded ...` the good volume before doing the `btrfs replace start ...` ? > I didn't see anything that said I had to and when I tested it without > mounting the volume it was able to replace the device without any issue. Is > that considered bad and could risk damage or has `replace` made it possible > to replace devices without umounting the filesystem?
No need to unmount, just replace old with new. Your scenario seems very convoluted and it’s pointless > 2) Everything I see about replacing a drive says to use `/old/device > /new/device` but what if the old device can't be read or no longer exists? > Would that be a `btrfs device add /new/device; btrfs balance start > /new/device` ? In case where old device is missing you’ve got few options: - if you have enough space to fit the data and enough of disks to comply with redundancy - just remove the drive, So for example is you have 3 x 1TB drives with raid 1 And use less than 1TB of data total - juste remove one drive and you will have 2 x 1TB drives in raid 1 and btrfs fill just rebalance stuff for you ! - if you have not enough space to fi the data / not enough disks left to comply with raid lever - your only option is to add disk first then remove missing (btrfs dev delete missing /mount_point_of_your_fs) > 3) When I have the RAID1 with two devices and I want to grow it out, which is > the better practice? Create a larger volume, replace the old device with the > new device and then do it a second time for the other device, or attaching > the new volumes to the label/uuid one at a time and with each one use `btrfs > filesystem resize devid:max /mountpoint`. You kinda misunderstand the principal of btrfs. Btrfs will span across ALL the available space you’ve got. If you have multiple devices in this setup (remember that partition IS A DEVICE), it will span across multiple devices and you can’t change this. Now btrfs resize is mean for resizing a file system occupying a device (or partition). So work flow is that is you want to shrink a device (partition) you first shrink fs on this device than size down the device (partition) … if you want to increase the size of device (partition) you increase size of device (partition) than you grow filesystem within this device (partition). This is 100% irrespective of total cumulative size of file system. Let’s say you’ve got a btrfs file system that is spanning across 3 x 1TB devices … and those devices are partitions. You have raid 1 setup - your complete amount of available space is 1.5 TB. Let’s say you want to shrink of of partitions to 0.5TB -> first you shrink FS on this partition (balance will runn automatically) -> you shrink partition down to 0.5TB -> from now on your total available space is 1.25TB. Simples right ? :) > Thanks > > > > > -- > To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in > the body of a message to majord...@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
