From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stan Hoeppner Subject: Re: Incredibly poor performance of mdraid-1 with 2 SSD Samsung 840 PRO Date: Mon, 22 Apr 2013 18:21:24 -0500 Message-ID: <5175C5F4.6060304@hardwarefreak.com> References: <5171CBF9.9020701@redhost.ro> <51725458.7020109@redhost.ro> <51732422.1050109@redhost.ro> <5173536C.2040108@hardwarefreak.com> <51743F14.7020404@hardwarefreak.com> <517488B7.9030505@hardwarefreak.com> Reply-To: stan@hardwarefreak.com Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: linux-raid-owner@vger.kernel.org To: Tommy Apel Cc: Andrei Banu , linux-raid Raid List-Id: linux-raid.ids On 4/22/2013 2:51 AM, Tommy Apel wrote: > Stan> > That was exactly what I was trying to show, that you result may vary > depending on data and backing device, as far as the raid1 goes it > doesn't care much for the data beeing passed through it. As I mentioned, this is true of the SandForce 2nd gen ASICs, maybe some others. The Samsung SSDs use a home grown Samsung controller which doesn't do compression. Its performance doesn't vary due to data content. Thus the performance gap you demonstrated doesn't apply to Andrei. We can eliminate this as a possible cause of his apparently horrible performance. And I think we can eliminate the regression in 2.6.32 as that patch seems to be included in his kernel, otherwise he'd likely not get 260MB/s in his dd raw read tests. The mystery continues... -- Stan