From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dave Chinner Subject: Re: Optimize RAID0 for max IOPS? Date: Tue, 25 Jan 2011 19:36:43 +1100 Message-ID: <20110125083643.GE28803@dastard> References: <20110118210112.D13A236C@gemini.denx.de> <4D361F26.3060507@stud.tu-ilmenau.de> <20110119192104.1FA92D30267@gemini.denx.de> <20110124215713.82D75B187@gemini.denx.de> <20110124230314.GA11040@dastard> <20110125083900.4dd65bf2@galadriel2.home> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: Content-Disposition: inline In-Reply-To: <20110125083900.4dd65bf2@galadriel2.home> Sender: linux-raid-owner@vger.kernel.org To: Emmanuel Florac Cc: Wolfgang Denk , linux-raid@vger.kernel.org, Justin Piszcz , xfs@oss.sgi.com List-Id: linux-raid.ids [ As a small note - if you are going to comment on the results table from a previous message, please don't cut it from your response. Context is important. I pasted the relevant part back in so i can refer back to it in my response. ] On Tue, Jan 25, 2011 at 08:39:00AM +0100, Emmanuel Florac wrote: > Le Tue, 25 Jan 2011 10:03:14 +1100 vous =E9criviez: > > > Version 1.96 ------Sequential Create------ --------Random = Create-------- > > > A1 -Create-- --Read--- -Delete-- -Create-- --Rea= d--- -Delete-- > > > files /sec %CP /sec %CP /sec %CP /sec %CP /sec= %CP /sec %CP > > > 16 104 0 +++++ +++ 115 0 89 0 +++++= +++ 111 0 > >=20 > > Only 16 files? >=20 > IIRC this is 16 thousands of files. Though this is not enough, I > generally use 80 to 160 for tests. Yes, you're right, the bonnie++ man page states that it is in units of 1024 files. Be nice if there was a "k" to signify that so people who aren't intimately familiar with it's output format can see exactly what was tested.... As it is, a create rate of 104 files/s (note the consistency of units between 2 adjacent numbers!) indicates something else is screwed, because my local test VM on RAID0 gets numbers like this: Version 1.96 ------Sequential Create------ --------Random Create= -------- test-4 -Create-- --Read--- -Delete-- -Create-- --Read--- -= Delete-- files /sec %CP /sec %CP /sec %CP /sec %CP /sec %CP = /sec %CP 16 25507 90 +++++ +++ 30472 97 25281 93 +++++ +++ 2= 9077 97 Latency 23864us 204us 21092us 18855us 82us = 121us IOWs, create rates of 25k/s and unlink of 30k/s and it is clearly CPU bound. Therein lies the difference: the original numbers have 0% CPU usage, which indicates that the test is blocking. Something is causing the reported test system to be blocked almost all the time. /me looks closer. Oh, despite $subject being "RAID0" the filesystems being tested are on RAID5 and RAID6 with very small chunk sizes on slow SATA drives. This is smelling like a case of barrier IOs on software raid on cheap storage.... Cheers, Dave. --=20 Dave Chinner david@fromorbit.com -- To unsubscribe from this list: send the line "unsubscribe linux-raid" i= n the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html