On Mon, Sep 21, 2009 at 8:38 PM, Linux Raid Study <linuxraid.study@xxxxxxxxx> 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 <snitzer@xxxxxxxxx> wrote: >> On Thu, Sep 17, 2009 at 8:37 AM, Michal Soltys <soltys@xxxxxxxx> wrote: >>> 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 alone? >>>> >>>> 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 accordingly to >>> the amount of disks present in the raid. If you do tests on a filesystem, >>> 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 parameters >>> 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 during >>> 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 boundary for >>> that to make any sense (and it doesn't have to be the case - for example 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). The last >> issue you mention (partitionable MD alignment offset) is also resolved >> 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@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html > -- Majed B. -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
