From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tom De Mulder Subject: Re: Software RAID and TRIM Date: Mon, 18 Jul 2011 11:53:59 +0100 (BST) Message-ID: References: <4E235984.2070704@5t9.de> Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed Return-path: In-Reply-To: <4E235984.2070704@5t9.de> Sender: linux-raid-owner@vger.kernel.org To: linux-raid@vger.kernel.org List-Id: linux-raid.ids On Sun, 17 Jul 2011, Lutz Vieweg wrote: > What is really an important factor for SSD performance: The controller. > The same SSDs perform with significantly lower latency for us when > connected to SATA controller channels than when connected to SAS > controllers (and they perform abysmal when used as hardware-RAID > constituents, in comparison). Interesting. I think it depends a lot on the controller. On a Dell server with PERC5/i RAID controller (actually made by LSI) I saw some performance degradation but not enough that I'd consider it a deal-breaker for situations where I really cared about the RAID functionality, more than about the loss of performance. After all, the latency is still massively lower than it is with spinning disk. I have a really great Areca RAID controller in a different server, but unfortunately it's in use and it'll be a while before I get another one I can use for testing. Given how well it does in other respects, I have high hopes for it. Best, -- Tom De Mulder - Cambridge University Computing Service +44 1223 3 31843 - New Museums Site, Pembroke Street, Cambridge CB2 3QH -> 18/07/2011 : The Moon is Waning Gibbous (83% of Full)