Le 08/11/2012 12:52, Felix Frank a écrit :
Hi,
On 11/08/2012 12:18 PM, "[SOLTECSIS] Carles Xavier Munyoz Baldó" wrote:
Hi,
We are creating a PROXMOX 2 cluster using DRBD and we have doubts about
which of the next options is better:
(A) DRBD over LVM.
(B) DRBD as a PV for LVM.
Which is the best option?
I remember that I have read that DRBD over LVM is not a recomended
configuration, but I don't remember why. I believe that I have readed
that in the DRBD documentation itself, but I'm not able to find it now.
Anyone knows if exists any kind of problem using DRBD over LVM?
it does work :-)
I'm not at all sure what's better performance-wise.
If your backing device is an LV, you do incur a write penalty to all
drbd interactions on both nodes.
Still, that doesn't mean that the setup will be slower than the other
way around.
It's usually a good idea to make your own tests, hopefully with a most
befitting workload.
I've been digging into this issue recently. There is some drbd
documentation with this scenario
(http://www.drbd.org/users-guide/s-lvm-lv-as-drbd-backing-dev.html), and
I have done such setup in the past. It does work, but I was wondering if
it is safe?
DRBD by default make use of barrier (unless no-disk-barrier is set with
a BBU RAID backend), and such barrier where not correctly implemented in
LVM before kernel 2.6.33. So I guess there are some cases where there is
problems, eg. with software MD raid.
Cheers,
Denis
Cheers,
Felix
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Denis Cardon
Tranquil IT Systems
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