From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from lists.gentoo.org (pigeon.gentoo.org [208.92.234.80]) by finch.gentoo.org (Postfix) with ESMTP id D8F881381F3 for ; Fri, 28 Jun 2013 09:12:49 +0000 (UTC) Received: from pigeon.gentoo.org (localhost [127.0.0.1]) by pigeon.gentoo.org (Postfix) with SMTP id 093C8E08E1; Fri, 28 Jun 2013 09:12:46 +0000 (UTC) Received: from plane.gmane.org (plane.gmane.org [80.91.229.3]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by pigeon.gentoo.org (Postfix) with ESMTPS id 382D0E08D1 for ; Fri, 28 Jun 2013 09:12:45 +0000 (UTC) Received: from list by plane.gmane.org with local (Exim 4.69) (envelope-from ) id 1UsUjS-0007qg-3R for gentoo-amd64@lists.gentoo.org; Fri, 28 Jun 2013 11:12:42 +0200 Received: from ip68-231-22-224.ph.ph.cox.net ([68.231.22.224]) by main.gmane.org with esmtp (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Fri, 28 Jun 2013 11:12:42 +0200 Received: from 1i5t5.duncan by ip68-231-22-224.ph.ph.cox.net with local (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Fri, 28 Jun 2013 11:12:42 +0200 X-Injected-Via-Gmane: http://gmane.org/ To: gentoo-amd64@lists.gentoo.org From: Duncan <1i5t5.duncan@cox.net> Subject: [gentoo-amd64] Re: Is my RAID performance bad possibly due to starting sector value? Date: Fri, 28 Jun 2013 09:12:24 +0000 (UTC) Message-ID: References: Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-Id: Gentoo Linux mail X-BeenThere: gentoo-amd64@lists.gentoo.org Reply-to: gentoo-amd64@lists.gentoo.org Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Complaints-To: usenet@ger.gmane.org X-Gmane-NNTP-Posting-Host: ip68-231-22-224.ph.ph.cox.net User-Agent: Pan/0.140 (Chocolate Salty Balls; GIT 368aae4 /usr/src/portage/src/egit-src/pan2) X-Archives-Salt: 32eca714-d711-4573-b8d6-e05557bd6142 X-Archives-Hash: 6ca26ba503d9b03768db7ce8d5ae759c Duncan posted on Fri, 28 Jun 2013 03:36:10 +0000 as excerpted: > So now I guess I send this and do some more testing of real device, now > that you've provoked my curiosity and I have the 50 GB (mostly) > pseudorandom file sitting in tmpfs already. Maybe I'll post those > results later. Well, I decided to use something rather smaller, both because I wanted to run it against my much smaller btrfs partitions on the ssd, and because the big file was taking too long for the benchmarks I wanted to do in the time I wanted to do them. I settled on a 4 GiB file. Speeds are power-of-10-based since that's what dd reports, unless otherwise stated. Sizes are power-of-2-based unless otherwise stated. This was filesystem-layer-based, not direct to device, and single I/O task, plus whatever the system might have had going on in the background. Also note that after reading the dd manpage, I added the conv=fsync parameter, hoping that gave me more accurate speed ratings due to the reducing the write-caching. SSD speeds, dual Corsair Neutron n256gp3 SATA-600 ssds, running btrfs raid1 data and metadata: To SSD: peak was upper 250s MB/s over a wide blocksize range of 1 MiB to 1GiB. I believe the btrfs checksumming might lower speeds here somewhat, as it's quite lower than the rated 450 MB/s sequential write speed. >From SSD: peak was lower 480s MB/s, blocksize 32 KiB to 512 KiB (smaller blocksize range but much smaller block than I expected). This is MUCH better, far closer to the 540 MB/s ratings. To/from SSD: At around 220 MB/s, peak was somewhat lower than write-only peak, as might be expected. Best-case blocksize range seemed to be 256 KiB to 2 MiB. So, best mixed-access case would seem to be a blocksize near 1 MiB. I did a few timed cps also, then did the math to confirm the dd numbers. They were close enough. Spinning rust speeds, single Seagate st9500424as, 7200rpm 2.5" 16MB buffer SATA-300 disk drive, reiserfs. Tests were done on a partition located roughly 40% thru the drive. I didn't test this one as closely and didn't do rust-to-rust tests at all, but: To rust: upper 70s MB/s, blocksize didn't seem to matter much. >From rust: upper 90s MB/s, blocksize upto 4 MiB. -- Duncan - List replies preferred. No HTML msgs. "Every nonfree program has a lord, a master -- and if you use the program, he is your master." Richard Stallman