From mboxrd@z Thu Jan 1 00:00:00 1970 From: Bill Davidsen Subject: Re: MD performance options: More =?windows-1252?Q?CPU=92s_or_?= =?windows-1252?Q?more_Hz=92s=3F?= Date: Mon, 09 Nov 2009 12:24:45 -0500 Message-ID: <4AF8505D.9060007@tmr.com> References: <66781b10911040149q165edf1s94a86f179f9af9fc@mail.gmail.com> <4AF18A39.6010404@tmr.com> <4AF19216.30300@Calva.COM> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <4AF19216.30300@Calva.COM> Sender: linux-raid-owner@vger.kernel.org To: John Hughes Cc: mark delfman , Linux RAID Mailing List List-Id: linux-raid.ids John Hughes wrote: > Bill Davidsen wrote: >> mark delfman wrote: >>> Hi... I am wondering if anyone can offer some advice on MD performance >>> related to CPU (speed and or cores). >> >> You didn't ask: if you use ext[34] filesystems, there is a gain to be >> had from tuning the stripe and stride parameters, at least for large >> sequential io. My measurements were on 2.6.26, so are out of date, >> but less head motion is always better. > An external journal can be a huge win for ext3 if you are doing lots > of file creates/deletes. (Striped raid, i.e. raid0/raid5/raid6/raid10 > doesn't help the journal much as it is used sequentially. In my tests > putting the journal on a raid1 and the rest of the fs on a raid10 > makes things go much faster. If you have enough disks of course :-)) You might try mounting with data=journal and see what performance you get with small reads and writes. Might surprise you. I hadn't thought of using raid1 (or raid0 if speed is more important than survival), but I have been playing with using SSD just for the journal. As you say, when you do lots of creates or deletes it makes a big difference. -- Bill Davidsen "We can't solve today's problems by using the same thinking we used in creating them." - Einstein