From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Majed B." Subject: Re: LVM and Raid5 Date: Mon, 21 Sep 2009 22:14:19 +0300 Message-ID: <70ed7c3e0909211214p3f38a602s2b0fac77a3da5cc1@mail.gmail.com> 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: Sender: linux-raid-owner@vger.kernel.org To: Linux Raid Study Cc: linux-raid@vger.kernel.org, linux-lvm@redhat.com List-Id: linux-raid.ids On Mon, Sep 21, 2009 at 8:38 PM, Linux Raid Study wrote: > Can I use LVM2 with kernel 2.6.27? > > Thanks everyone! Can you be more specific?! If it's just in general, then yes. If you want to use with RAID, then also yes. >> On Mon, Sep 21, 2009 at 7:33 AM, Mike Snitzer wr= ote: >> On Thu, Sep 17, 2009 at 8:37 AM, Michal Soltys wro= te: >>> Linux Raid Study wrote: >>>> >>>> Hello: >>>> >>>> Has someone experimented with LVM and Raid5 together (on say, 2.6.= 27)? >>>> Is there any performance drop if LVM/Raid5 are combined vs Raid5 a= lone? >>>> >>>> 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 accordin= gly to >>> the amount of disks present in the raid. If you do tests on a files= ystem, >>> you may see significant differences due to that. YMMV depending on = the type >>> of used benchmark(s). >>> >>> - filesystem awareness of underlying raid >>> >>> For example, xfs created on top of raid, will generally get the par= ameters >>> right (stripe unit, stripe width), but if it's xfs on lvm on raid, = then 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 du= ring >>> pvcreate (by default it's 192KiB, so with non-default stripe unit i= t may >>> cause issues, although I vaguely recall posts that current LVM is M= D aware >>> during initialization). Of course LVM must itself start at the boun= dary for >>> that to make any sense (and it doesn't have to be the case - for ex= ample if >>> you use partitionable MD). >> >> All of the above have been resolved in recent LVM2 userspace (2.02.5= 1 >> being the most recent release with all these addressed). =C2=A0The l= ast >> issue you mention (partitionable MD alignment offset) is also resolv= ed >> 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"= in > the body of a message to majordomo@vger.kernel.org > More majordomo info at =C2=A0http://vger.kernel.org/majordomo-info.ht= ml > --=20 Majed B. -- 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