[CentOS] XFS and LVM2 (possibly in the scenario of snapshots)
timo.schoeler at riscworks.net
Wed Dec 9 15:39:53 UTC 2009
thus Ross Walker spake:
> On Dec 9, 2009, at 8:05 AM, Timo Schoeler
> <timo.schoeler at riscworks.net> wrote:
>> Hi list,
>> during the last days there was a discussion going on about the
>> of XFS; though I myself used XFS heavily and didn't run into issues
>> I'd like to ask something *before* we create our next generation data
>> storage backend...
>> Les Mikesell wrote in  about issues in the combination of XFS and
>> -- however, it was being discussed in context of using 32bit kernels.
>> What I specifically need is to run XFS (or something similar, I am
>> forced to use XFS, but it was my preference for some years now, and I
>> didn't have any issues with it yet) on top of LVM to be able to create
>> snapshots. We're talking about several file systems of a size at about
>> 4TiByte each.
>> On another place  I read that there were issues with that.
>> Can anyone shed some light on this? Would be very appreciated.
> There is no problem if it is done on x86_64 with it's 8k stack frames,
> but on i386 with it's 4k stack frames you could run into a stack
> overflow when doing it on top of stackable block devices (md raid,
> lvm, drbd, etc).
> Also since the current LVM on CentOS doesn't support barriers (next
> release I believe) journalling isn't safe on LVM unless you are using
> a storage controller with BBU write-back cache.
> I have heard anyways that the current implementation of barriers isn't
> very performant and doesn't take into consideration controllers with
> BBU cache, so most people will end up mounting with nobarriers which
> just means they are in the same boat as they are now. Better make sure
> your machine is bullet proof as a power outage or a kernel panic can
> spell disaster for XFS (or any other file system really).
> It is better to invest in a good hardware RAID controller until the
> whole barriers stuff is ironed out. It should really perform better
> then it does.
Thanks for your detailed explanation, that really clears things up;
however, I was intending to build a software RAID10 as we had really not
so good experiences on hw RAID controllers int the past (for all kinds
Would barriering here still be a problem then?
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