From owner-freebsd-fs@FreeBSD.ORG Mon Nov 8 22:31:18 2010 Return-Path: Delivered-To: freebsd-fs@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 97B08106564A for ; Mon, 8 Nov 2010 22:31:18 +0000 (UTC) (envelope-from freebsd-fs@m.gmane.org) Received: from lo.gmane.org (lo.gmane.org [80.91.229.12]) by mx1.freebsd.org (Postfix) with ESMTP id 189F68FC26 for ; Mon, 8 Nov 2010 22:31:17 +0000 (UTC) Received: from list by lo.gmane.org with local (Exim 4.69) (envelope-from ) id 1PFaF8-0006WG-A0 for freebsd-fs@freebsd.org; Mon, 08 Nov 2010 23:31:14 +0100 Received: from cpe-188-129-102-227.dynamic.amis.hr ([188.129.102.227]) by main.gmane.org with esmtp (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Mon, 08 Nov 2010 23:31:14 +0100 Received: from ivoras by cpe-188-129-102-227.dynamic.amis.hr with local (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Mon, 08 Nov 2010 23:31:14 +0100 X-Injected-Via-Gmane: http://gmane.org/ To: freebsd-fs@freebsd.org From: Ivan Voras Date: Mon, 08 Nov 2010 23:30:59 +0100 Lines: 40 Message-ID: References: <4CD04AEC.8040607@aldan.algebra.com> <4CD051A9.7090200@freebsd.org> <4CD0660E.2000102@aldan.algebra.com> <4CD06C4B.80100@freebsd.org> <4CD0895A.5030402@aldan.algebra.com> <4CD09830.3030400@freebsd.org> <4CD48F81.1080201@aldan.algebra.com> <4CD5A5B7.4040006@aldan.algebra.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Complaints-To: usenet@dough.gmane.org X-Gmane-NNTP-Posting-Host: cpe-188-129-102-227.dynamic.amis.hr User-Agent: Mozilla/5.0 (X11; U; FreeBSD amd64; en-US; rv:1.9.2.12) Gecko/20101102 Thunderbird/3.1.6 In-Reply-To: <4CD5A5B7.4040006@aldan.algebra.com> Subject: Re: iozone-ing an SSD (Re: Using an SSD "disk" for /) X-BeenThere: freebsd-fs@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Filesystems List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 08 Nov 2010 22:31:18 -0000 On 11/06/10 20:00, Mikhail T. wrote: > On 11/5/2010 7:13 PM, Mikhail T. wrote: >> The results can be found in 4 HTML files found at: >> http://aldan.algebra.com/~mi/io/ (The original iozone-created Excel >> files are there too.) That server doesn't respond! > I added some more iozone runs, as well as those of rawio. These are much > fewer (as file-system parameters don't affect rawio) and easier to > interpret: > > * It makes no difference to the SSD, whether your access is random > or sequential And this is their biggest strength. All others - like "raw" IO speed, are in the majority of serious use cases secondary to that. > * SSD clearly beats the HD in rawrite, although, at "only" 88Mb/sec, > the results are far from the marketing... Basically, you should be looking at IOPS, not MB/s. > * SSD connected to plain SATA port strongly beats the same SSD > connected to the fancy SAS controller (mpt) Not really surprising. The controller might be too smart for its own good in this simple case. But there could be other, more important resons, like the controller disabling the drive's (in this case, SSD's) write caching, which the majority of "real" RAID controllers do by default. Leaving the drive's write cache turned on puts your data at risk (which is important if you are running servers). You can sort of verify this hypothesis by setting this loader tunable: hw.ata.wc=0 - this should disable the disk write cache for (S)ATA drives.