> Not at all. You can achieve this performance with the 6 300GB spindles > you currently have, as Christoph and I both mentioned. You simply lose > one spindle of capacity, 300GB, vs your current RAID6 setup. Make 3 > RAID1 pairs in the p400 and concatenate them. If the p400 can't do this > concat the mirror pair devices with md --linear. Format the resulting > Linux block device with the following and mount with inode64. > > $ mkfs.xfs -d agcount=3 /dev/[device] > > That will give you 1 AG per spindle, 3 horizontal AGs total instead of 4 > vertical AGs as you get with default striping setup. This is optimal > for your high IOPS workload as it eliminates all 'extraneous' seeks > yielding a per disk access pattern nearly identical to EXT4. And it > will almost certainly outrun EXT4 on your RAID6 due mostly to the > eliminated seeks, but also to elimination of parity calculations. > You've wiped the array a few times in your testing already right, so one > or two more test setups should be no sweat. Give it a go. The results > will be pleasantly surprising. Well I had to move around quite a bit of data, but for the sake of completeness, I had to give it a try. With a nice and tidy fresh XFS file system, performance is indeed impressive – about 16 sec for the same task that would take 2 min 25 before. So that’s about 150 MB/sec, which is not great, but for many tiny files it would perhaps be a bit unreasonable to expect more. A simple copy of the tar onto the XFS file system yields the same linear performance, the same as with ext4, btw. So 150 MB/sec seems to be the best these disks can do, meaning that theoretically, with 3 AGs, it should be able to reach 450 MB/sec under optimal conditions. I will still do a test with the free space fragmentation priming on the concatenated AG=3 volume, because it seems to be rather slow as well. But then I guess I’m back to ext4 land. XFS just doesn’t offer enough benefits in this case to justify the hassle. _______________________________________________ xfs mailing list xfs@xxxxxxxxxxx http://oss.sgi.com/mailman/listinfo/xfs
