From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from cuda.sgi.com (cuda2.sgi.com [192.48.176.25]) by oss.sgi.com (8.12.11.20060308/8.12.11/SuSE Linux 0.7) with ESMTP id mBF5b4JK020256 for ; Sun, 14 Dec 2008 23:37:04 -0600 Received: from ipmail05.adl2.internode.on.net (localhost [127.0.0.1]) by cuda.sgi.com (Spam Firewall) with ESMTP id 4BFBE1EDD6 for ; Sun, 14 Dec 2008 21:37:01 -0800 (PST) Received: from ipmail05.adl2.internode.on.net (ipmail05.adl2.internode.on.net [203.16.214.145]) by cuda.sgi.com with ESMTP id V1iytyiGKxL34lGs for ; Sun, 14 Dec 2008 21:37:01 -0800 (PST) Date: Mon, 15 Dec 2008 16:36:57 +1100 From: Dave Chinner Subject: Re: XFS over SSD Message-ID: <20081215053656.GE32301@disturbed> References: <5d96567b0812080442r131d9fc8t4019c99ffbffa290@mail.gmail.com> <493D334C.5010006@sandeen.net> <5d96567b0812080711x34bb93d6vd8e4f88d9b190e9@mail.gmail.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <5d96567b0812080711x34bb93d6vd8e4f88d9b190e9@mail.gmail.com> List-Id: XFS Filesystem from SGI List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: xfs-bounces@oss.sgi.com Errors-To: xfs-bounces@oss.sgi.com To: Raz Cc: linux-xfs@oss.sgi.com, Eric Sandeen On Mon, Dec 08, 2008 at 05:11:58PM +0200, Raz wrote: > On Mon, Dec 8, 2008 at 4:46 PM, Eric Sandeen wrote: > > Raz wrote: > >> I am thinking of using XFS over a SSD disk. > >> 1. Can I separate xfs meta data ( not just the logging) from the SSD ? > >> can I put the meta on a different disk ? > > > > Are you talking about just the log (see the mkfs man page for external > > logs, as Justin suggested) or all metadata? For the latter, using the > > realtime subvolume does accomplish this (data on one volume, metadata on > > the other) but that's not used very often. > > > > -Eric > > > I am referring to all the meta data. 128K of erase block for some block map > update is a big penalty. That's not an issue for smart SSDs like the intel one. They internally use a log-based structure that means that small writes don't end up requiring an entire erase block to be rewritten. That is, they have a low write amplification factor. Such SSDs don't really care that much about the filesystem structure and random write patterns. Older/cheaper SSDs have a much larger write amplification factor and so are unsuited to traditional filesystem structures..... Google "SSD write amplification" for more information. Cheers, Dave. -- Dave Chinner david@fromorbit.com _______________________________________________ xfs mailing list xfs@oss.sgi.com http://oss.sgi.com/mailman/listinfo/xfs