From mboxrd@z Thu Jan 1 00:00:00 1970 From: Bill Davidsen Subject: Re: md software raid Date: Tue, 27 Oct 2009 16:52:23 -0400 Message-ID: <4AE75D87.60708@tmr.com> References: <26023091.post@talk.nabble.com> <20091023093820.GA7613@cthulhu.home.robinhill.me.uk> <000601ca56ee$f7a4d360$e6ee7a20$@com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <000601ca56ee$f7a4d360$e6ee7a20$@com> Sender: linux-raid-owner@vger.kernel.org To: Ian Docherty Cc: 'Robin Hill' , linux-raid@vger.kernel.org List-Id: linux-raid.ids Ian Docherty wrote: > >> -----Original Message----- >> From: linux-raid-owner@vger.kernel.org [mailto:linux-raid- >> owner@vger.kernel.org] On Behalf Of Robin Hill >> Sent: 23 October 2009 10:38 >> To: linux-raid@vger.kernel.org >> Subject: Re: md software raid >> >> On Fri Oct 23, 2009 at 02:11:09AM -0700, ian.d wrote: >> >> >>> hello >>> >>> As a newbie to Linux kernel etc. >>> >>> How do you tell which version of md software raid is included in a >>> specific kernel version? >>> Is there a command to run which will return this info? >>> Is it possible to install different versions of md in different >>> >> kernels? >> >> There's two separate components to Linux software RAID - the md code in >> the kernel, and the mdadm application which interfaces with it. I very >> much doubt the kernel code is versioned at all, other than by the >> kernel version (or GIT version). The mdadm application is versioned, >> and you can get the installed version by running 'mdadm -V'. >> >> Some of the mdadm functionality will only work with newer kernel >> versions, but you should be able to run any version with any kernel >> (within reason anyway) and make use of the core functionality. There >> may be some exceptions here, but they should be detailed in the release >> notes for specific versions. >> >> As for changing the md version in the kernel - it may be possible, but >> generally there's a lot of work involved in back/forward porting code >> between kernel versions (because of changes to core structures, etc). >> >> Is there any particular reason you're asking this (e.g. needing to use >> some of the latest functionality with an older kernel)? You may get a >> more definitive answer if you have a specific case. >> > > Thanks this info was very helpful. > > The reason I asked was because I have been following a thread re MD-XFS 50% > write performance issue with different kernel releases and as performance is > important to me I was thinking it might be better for me to use an older > kernel (2.6.28.4) but keeping md,mdadm functionality up to date > That's certainly a valid point, if you are stuck using xfs by preference or requirement. I have seen claims that 2.6.32 will be better, but I have no intention of testing it, having parted company with xfs a while ago. -- Bill Davidsen Unintended results are the well-earned reward for incompetence.