On Wed, 14 Sep 2011, Chris Samuel <chris@csamuel.org> wrote:
ZFS appeared to be using a lot more CPU than ext4 though.. not sure what to make of that..
Well it has to checksum all data being written to disk, and verify the checksums of anything being read back from disk.
[521878.448007] raid6: int64x1 2043 MB/s [521878.516018] raid6: int64x2 2160 MB/s [521878.584012] raid6: int64x4 1894 MB/s [521878.652042] raid6: int64x8 1599 MB/s [521878.720007] raid6: sse2x1 4056 MB/s [521878.788004] raid6: sse2x2 4831 MB/s [521878.856005] raid6: sse2x4 7119 MB/s [521878.856007] raid6: using algorithm sse2x4 (7119 MB/s) I just loaded the raid6 module on my E4600 (2*2.4GHz) system. Apparently the RAID-6 operations which are probably more computationally intensive than any basic checksum can be performed at a rate of 7GB/s. As the transfer rates for a SQL test are probably a couple of orders of magnitude less than that I doubt that checksums are enough to explain the CPU use. -- My Main Blog http://etbe.coker.com.au/ My Documents Blog http://doc.coker.com.au/