From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christopher Chen Subject: Re: raid10 layout for 2xSSDs Date: Mon, 16 Nov 2009 08:08:49 -0800 Message-ID: <7bc80d500911160808o4ca4d335gdeeb50fff61b2149@mail.gmail.com> References: <1258381745.31633.35.camel@localhost> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Return-path: In-Reply-To: <1258381745.31633.35.camel@localhost> Sender: linux-raid-owner@vger.kernel.org To: Kasper Sandberg Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids On Mon, Nov 16, 2009 at 6:29 AM, Kasper Sandberg wrote: > Hello. > > I've been wanting to create a raid10 array of two SSDs, and I am > currently considering the layout. > > As i understand it, near layout is similar to raid1, and will only > provide a speedup if theres 2 reads at the same time, not a single > sequential read. > > so the choice is really between far and offset. As i see it, the > difference is, that offset tries to reduce the seeking for writing > compared to far, but that if you dont consider the seeking penalty, > average sequential write speed across the entire array should be roughly > the same with offset and far, with offset perhaps being a tad more > "stable", is this a correct assumption? if it is, that would mean offset > provides a higher "garantueed" speed than far, but with a lower maximum > speed. Do you plan to have more than two devices in the array? Raid 10 isn't magic. If you don't have more than do devices, I suppose your seek time might be half for reads (and higher for writes), but you won't be able to do any striping. I'm a bit confused as to the number of people popping in recently wanting to run raid 10 on two disk "arrays". cc -- Chris Chen "The fact that yours is better than anyone else's is not a guarantee that it's any good." -- Seen on a wall