On 1/20/2012 1:30 AM, Konrad Rzepecki wrote: > W dniu 20.01.2012 01:39, Stan Hoeppner pisze: >> On 1/19/2012 5:07 AM, Konrad Rzepecki wrote: >>> Yes, you have right. But I found recently, that disk mounted on my >>> server are slow 5.9K. My tests on in shows that they do fsync 1.5x-2x >>> slower than 7.2K with quite often 5x-10x slower peak. Together with >>> raid10, lvm, ext4, and much heavier load during delivery it may give >>> effect I'm observing. >> >> 5.9K RPM? Bingo. There's the problem. Those are "green" drives, from >> one manufacturer or another, probably Western Digital EARS 2TB drives. >> They are not suitable for RAID use, nor server use, nor any high >> performance use whatsoever. As you've seen first hand their performance >> is low, unpredictable, and unreliable. > > I have Seagate Barracude LP 1.5TB drives.
These are 512 byte/sector drives so no alignment issues. And AFAIK they don't use variable spindle speed like the WD drives. If indeed the drives are a big factor in your poor fsync performance, then I'd guess there's something in their firmware causing it. They're squarely targeted at low performance desktop applications and low power consumption, so firmware tuning for such applications seems a likely cause of poor random IOPS performance. >> Needless to say, you're not going to get decent queue spooling >> performance with these green drives, ever. If you can't wholesale swap >> these 8 drives for units suitable for mail server duty, consider >> sticking two small inexpensive 7.2k SATA drives in the box and mirroring >> them.... > >> This is likely the least expensive way, in both $$ and effort, to solve >> your problem. > > But, unfortunately, impossible, a last for now. I make, from some time, > changes in my sending software. I hope this workaround will be enough. As someone else mentioned, Ralf IIRC, if you can submit via SMTP instead of pickup you can cut your fsync load in half. I'd focus efforts there. > Anyway, thanks for your help. Sure thing. In closing, it's hard to imagine those Seagate LP drives are that horrible. It would be interesting to see how a single one of them performed as a queue drive. If you tested that and fsyncs are relatively decent, then we could look at diagnosing problems with your mdraid/LVM stack over on the linux-raid mailing list. I assume you're using mdraid and not a RAID card. You never confirmed which. -- Stan
