From mboxrd@z Thu Jan 1 00:00:00 1970 From: Bill Davidsen Subject: Re: Linux and SSD and how to decrease io delay : question, please Date: Tue, 04 Mar 2008 11:56:04 -0500 Message-ID: <47CD7F24.7090601@tmr.com> References: <303475.18445.qm@web35709.mail.mud.yahoo.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <303475.18445.qm@web35709.mail.mud.yahoo.com> Sender: linux-raid-owner@vger.kernel.org To: Mariella Petrini , Linux RAID List-Id: linux-raid.ids > DanielMariella Petrini wrote: > Hi, > > I have run a benchmark using the latest Linux kernel > and having > still the elevator set to noop (for each hard drive) > and vm.dirty_expire_centisecs = 6000 > > The system has 24GB of RAM, 2 SSD Mtron drives on a > RAID controller. > The databases are spread across two ext3 filesystems > mounted on the SSD drives (one filesystem maps to one > SSD drive and the other one to the other SSD drive. > Each drive is seen as a single volume). > The system has 2 cpus with 2 cores each. > > Have you mounted those filesystem with the "noatime" option? If you don't do that you risk causing a *lot* of unwanted seek and write activity to the journal. > Before starting each benchmark the system has > approximately 16GB of RAM already cached (so that most > of the file reads are reduced) > -- Bill Davidsen "Woe unto the statesman who makes war without a reason that will still be valid when the war is over..." Otto von Bismark