[DRBD-user] Layering drbd8 and LVM2 to minimize split-brain

Kelly Byrd kbyrd-drbd at memcpy.com
Mon Oct 15 00:22:15 CEST 2007

Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.




On Mon, 15 Oct 2007 00:12:32 +0200, Rene Mayrhofer
<rene.mayrhofer at gibraltar.at> wrote:
> On Sonntag 14 Oktober 2007, Kelly Byrd wrote:
>> > c) Using drbd8 volumes as the Xen backend devices, on top of LVM2.
> That
>> > is,
>> > both cluster nodes hold one (or two, the second one for swap) LV(s)
> for
>> > each
>> > Xen domU and those are synced with one drbd8 primary/secondary volume
>> > each.
>>
>> I do this with VMware Server:
>> - Big storage (raid0, raid5, raid10, whatever) as /dev/md0
>> - One volume group, many logical volumes.
>> - One drbd resource (pri/sec) per logical volume, make a filesystem on
>> this.
>> - One VM per drbd.
>>
>> With this, I avoid pri/pri, but I can still migrate VMs one at a time
>> from node to node.
> 
> And this construction is stable for you? How many drbd resources do you
> have 
> running? On which hardware, with which kernel, if you don't mind me
> asking?
> 
> I am currently running Debian etch on HP servers (with 3/4 GB RAM and
> raid1 
> storage backends for the volume groups - one at each node), but it's far
> from 
> stable, and all crashes/hangs/reboots in the last few months were caused
> by 
> drbd in one form or the other.
> 

I just went into production after a month or so of testing various
configurations. Lars suggested the above.

- I'm running 22 drbds, approx 90GB each, with XFS on each.

- Stable? So far. My torture test was to do full syncs while doing iozone
in the VMs. Worked great many many times.

- OS details: CentOS5 with the 2.6.18-8.1.14.el5.centos.plus kernel.

- DRBD is 8.0.4 also from the centosplus repository.

- I'm running on cheap servers a couple of SuperMicro 5015. 1U boxes
with a singel Intel quad core CPU, 8GB of ram and four 500GB sata
drives each.








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