From mboxrd@z Thu Jan 1 00:00:00 1970 From: Linux Raid Study Subject: Re: LVM and Raid5 Date: Mon, 21 Sep 2009 10:38:01 -0700 Message-ID: References: <4AB22DA3.2090901@ziu.info> <170fa0d20909210733p2e3e797cvb60af2e9bd153fda@mail.gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: <170fa0d20909210733p2e3e797cvb60af2e9bd153fda@mail.gmail.com> Sender: linux-raid-owner@vger.kernel.org To: Mike Snitzer Cc: Michal Soltys , linux-raid@vger.kernel.org, linux-lvm@redhat.com List-Id: linux-raid.ids Can I use LVM2 with kernel 2.6.27? Thanks everyone! On Mon, Sep 21, 2009 at 7:33 AM, Mike Snitzer wrote= : > On Thu, Sep 17, 2009 at 8:37 AM, Michal Soltys wrot= e: >> Linux Raid Study wrote: >>> >>> Hello: >>> >>> Has someone experimented with LVM and Raid5 together (on say, 2.6.2= 7)? >>> Is there any performance drop if LVM/Raid5 are combined vs Raid5 al= one? >>> >>> Thanks for your inputs! >> >> Few things to consider when setting up LVM on MD raid: >> >> - readahead set on lvm device >> >> It defaults to 256 on any LVM device, while MD will set it according= ly to >> the amount of disks present in the raid. If you do tests on a filesy= stem, >> you may see significant differences due to that. YMMV depending on t= he type >> of used benchmark(s). >> >> - filesystem awareness of underlying raid >> >> For example, xfs created on top of raid, will generally get the para= meters >> right (stripe unit, stripe width), but if it's xfs on lvm on raid, t= hen it >> won't - you will have to provide them manually. >> >> - alignment between LVM chunks and MD chunks >> >> Make sure that extent area used for actual logical volumes start at = the >> boundary of stripe unit - you can adjust the LVM's metadata size dur= ing >> pvcreate (by default it's 192KiB, so with non-default stripe unit it= may >> cause issues, although I vaguely recall posts that current LVM is MD= aware >> during initialization). Of course LVM must itself start at the bound= ary for >> that to make any sense (and it doesn't have to be the case - for exa= mple if >> you use partitionable MD). > > All of the above have been resolved in recent LVM2 userspace (2.02.51 > being the most recent release with all these addressed). =C2=A0The la= st > issue you mention (partitionable MD alignment offset) is also resolve= d > when a recent LVM2 is coupled with Linux 2.6.31 (which provides IO > Topology support). > > Mike > -- To unsubscribe from this list: send the line "unsubscribe linux-raid" i= n the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html