Is it possible to combine different drives in Btrfs?
It is possible to combine drives with different size in btrfs. But currently btrfs does not handel ENOSPC (No space left on device) very well. E.g.
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.
Is it possible to pair all chunks of Btrfs?
BTRFS allocates chunks to devices in a round-robin fashion, which can cause lost space if you have devices of different sizes. There is a quasi-round-robin patch in the pipeline to improve on this. Of course, it is still impossible to pair all chunks on different devices if you have a 500GB and a 2TB disk.
How big is a multi-device Btrfs file server?
It depends on what profile you use for the data blocks of the multi-device Btrfs filesystem. When you use RAID0 (the default for data blocks), each disks can only be filled up to the capacity of the smallest disk in the array. I have a file server with a 2TB and a 3TB disk. It boots Ubuntu 12.10 from a USB flash drive.
What does Btrfs device delete missing mean in raid XX?
btrfs device delete missing tells btrfs to remove the first device that is described by the filesystem metadata but not present when the FS was mounted. In case of RAID XX layout, you cannot go below the minimum number of the device required. So before removing a device (even the missing one) you may need to add a new one.
How many devices do I need for Btrfs to work?
For a RAID 6, the minimum is 4 devices. mkfs.btrfs will accept more than one device on the command line. It has options to control the RAID configuration for data ( -d) and metadata ( -m ).
When does Btrfs need to be mounted in degraded mode?
But, if a device is missing or the super block has been corrupted, the filesystem will need to be mounted in degraded mode: btrfs device delete missing tells btrfs to remove the first device that is described by the filesystem metadata but not present when the FS was mounted.