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Can you use RAID-1 on a Btrfs device?
Basically if your Btrfs device had RAID-1 and you convert it you normal single mode, your disk space will double: This is a pretty nice feature that is made possible by the unique design in Btrfs. For example ZFS does not have a balance command at all.
How many disks can I use in Btrfs?
In traditional mdadm based RAID if you have two 1 TB disks configured to mirror each other in RAID 1 mode, and you want to expand this setup, you basically need to install two more disks, and they need to be of equal size. In btrfs, life is much more flexible.
Do you need Btrfs for a serverfirst?
You might want to read The perfect Btrfs setup for a serverfirst, and maybe also Using RAID with btrfs and recovering from broken disksand Using Btrfs with Multiple Devices, and Restoring UEFI Boot Entry after Ubuntu Update. What this page offers over the others is a little better coverage of EFI issues, and how to deal with a failed disk.
What can I use Btrfs for in Linux?
Btrfs includes a lot of interesting functionality and replaces traditional Linux disk and filesystem tools like LVM (volume manager, disk snapshots) and mdadm (software RAID).
Can a single device be used as a Btrfs Mount?
(See btrfs-space-calculator or btrfs disk usage calculator) Non-striped equivalents may give you a more effective use of space (single instead of RAID 0, RAID 1 instead of RAID 10). Once you create a multi-device filesystem, you can use any device in the FS for the mount command:
What happens if a disk fails in Btrfs?
If a disk in a btrfs RAID 1 array fails, then btrfs will refuse to mount that filesystem and error messages will be visible in the syslog. If it was the root filesystem, then the system will refuse to boot normally and the system will usually boot to an initramfs console.
What to do when a disk in a RAID array fails?
The correct thing to do when a disk in an RAID array fails, is to replace it. Once you have a new disk in place notify btrfs about it with the command: This command reads files both from the original drive (if still accessible) and from other disks in the RAID array, and uses that information to populate the new clean disk.
What to do when Btrfs won’t Mount?
In cases where the physical disk has not failed but instead something in the btrfs journal or checksum trees is corrupted and does not match, and the filesystem refuses to mount, this is the recommended procedure to try: First make a backup the volume. After that try to mount the volume in the read-only recovery mode:
How much disk space do I need with Btrfs?
Btrfs will make sure that as RAID 1 mandates, each file will exist in two copies and those copies are stored on physically different disks. If you would expand the two 1 TB array with one 1 TB disk, then btrfs would give you 1,5 TB of usable disk space in total while still satisfying the RAID 1 replicate requirements.
How is a non-RAID filesystem converted to a raid?
A non-RAID filesystem is converted to RAID by adding a device and running a balance filter that will change the chunk allocation profile. For example, to convert an existing single device system ( /dev/sdb1) into a 2 device RAID 1 (to protect against a single disk failure):
Which is an example of using btrfs with multiple devices?
The btrfs balance operation will take some time. It reads in all of the FS data and metadata and rewrites it across all the available devices. Depending on the usage scenario that is not needed, one example would be adding a new device to a RAID 1 filesystem whose existing devices still have enough space left.