Is there an option in btrfs for this mode of RAID? I know it supports the equivalent of RAID10, but what I am after is JBOD of mirrors. The reason I want this is for making a really low power home NAS, typically for home theater/media use. I believe this would yield better power savings in the average case.
Here is my reasoning. This sort of a setup would be idle most of the time, and the disks can safely be spun down. When a request comes to read a file (typically a multi-MB or multi-GB sequentially read file), in RAID0 all the disks would wake up because each chunk would come off as different disk. In JBOD, only the disk that has the file on it would need to be awake to serve that file while the rest can go to sleep. Of course JBOD yields relatively poor performance, but since an average SATA disk will saturate a Gb ethernet link with a linear read (the sort that I envisage my storage box doing most of the time), performance isn't really an issue. I know I can create two RAID0 stripes and create a BTRFS mirror on top of that, but if I were to do that, then a disk failure would mean re-mirroring the entire stripe instead of just one disk, which is not a sane solution on a big multi-TB array. Is there a way to do this with BTRFS? Gordan -- 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
