Messages in this thread | | | Date | Wed, 8 Jan 2014 07:26:10 -0800 | From | Christoph Hellwig <> | Subject | Re: Terrible performance of sequential O_DIRECT 4k writes in SAN environment. ~3 times slower then Solars 10 with the same HBA/Storage. |
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On Wed, Jan 08, 2014 at 04:43:07PM +0200, Sergey Meirovich wrote: > Results are almost the same: > 14.68Mb/sec 3758.02 Requests/sec >
On my laptop SSD I get the following results (sometimes up to 200MB/s, sometimes down to 100MB/s, always in the 40k to 50k IOps range):
time elapsed (sec.): 5 bandwidth (MiB/s): 160.00 IOps: 40960.00
The IOps are more than the hardware is physically capable of, but given that you didn't specify O_SYNC this seems sensible given that we never have to flush the disk cache.
Could it be that your array has WCE=0? In Linux we'll never enable the cache automatically, but Solaris does at least when using ZFS. Try running:
sdparm --set=WCE /dev/sdX
and try again.
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