Re: Incredibly poor performance of mdraid-1 with 2 SSD Samsung 840 PRO

[Stan Hoeppner <stan@hardwarefreak.com>]

On 4/22/2013 7:02 AM, Tommy Apel wrote:
> Yes it can be run as it is, it will write to the file given by --filename=
> 
> well from what I make of it so far I wouldn't rule out the bad device
> part but at the same time there could be other things involved
> although I don't belive it to be the md part
> 
> Stan> do you know anything about the state of ext4 on centos 6.x ?

Enough to assume it's not part of the problem here.  Andrei's hdparm
below the filesystem layer throughput is bouncing up/down by ~100MB/s
depending on when he runs it.

If he's using LVM and has active snapshots that would definitely cause
some extra load, but in that case given his 3 RAID1 pairs it should
affect both drives equally.  And that's not what we're seeing.

I hope my last post gets him closer to identifying the problem.  The
perf top and iotop data doing $bigfile copy should be instructive.

-- 
Stan