[ ... ] > a ten disk raid1 using 7.2k 3 TB SAS drives Those are really low IOPS-per-TB devices, but good choice for SAS, as they will have SCT/ERC.
> and used aio to test IOOP rates. I was surprised to measure > 215 read and 72 write IOOPs on the clean new filesystem. For that you really want to use the 'raid10' profile, 'raid1' is quite different, and has an odd recovery "gotcha". Also so far 'raid1' in Btrfs only reads from one of the two mirrors per thread. Anyhow the 72 write IOPS look like single member device IOPS rate and that's puzzling, as if Btrfs is not going multithreading to a many-device 'raid1' profile volume. I have a 6-device test setup at home and I tried various setups and I think I got rather better than that. > Sequential writes ran as expected at roughly 650 MB/s. That's a bit too high: on single similar drive I get around 65MB/s average with relatively large files, I would expect around 4-5x that from a 10-device mirrored profile, regardless of filesystem type. I strongly suspect that we have a different notion of "IOPS", perhaps either logical vs. physical IOPS, or randomish vs. sequentialish IOPS. I'll have a look at your attachments in more detail. > I created a zfs filesystem for comparison on another > checksumming filesystem using the same layout and measured > IOOP rates at 4315 read, 1449 write with sync enabled (without > sync it's clearly just writing to RAM), sequential performance > was comparable to btrfs. It seems unlikely to me that you got that with a 10-device mirror 'vdev', most likely you configured it as a stripe of 5x 2-device mirror vdevs, that is RAID10. -- 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
