[DRBD-user] memory requirements for DRBD

Bruno Voigt Bruno.Voigt at ic3s.de
Fri Jan 23 17:59:47 CET 2009


Hi,

I'm looking for some figures:

What are the memory requirements/guidelines for DRBD resources?
What are the maxima for normal operation, sync, verify ?
Is it dependent on the size of the replicated device?
Does the requirements increase lineary with each resource ?

I'm playing with a Debian lenny/unstable system pair (HP DL360 G5, 8G RAM)
with linux 2.6.18.6 (or 2.6.26.1), xen 3.2.1, DRBD 8.3.0,
hosting 13 DomU - each with 2 DRBD-Devices (4G disk+512M swap)
allocated from LVM LVs each separately replicated with DRBD.

The Dom0 got a fixed amount of memory (1 G via grub menu.list
xenhopt=dom0_mem=1024M)
and I've seen the situation that the Out-of-memory killer strikes on the
node A
if all DRBD resources are synced (all at once) from node A to  initially
connected node B.

Nothing else besides an small apache is running on the Dom0,
in disconnected mode there is over 600M available on node a.

If I sync the resources one by one the OOM can be prevented.

So I'm looking for a solid based way to size the RAM of the Dom0 ..

Thanks for any hints,
WR,
Bruno



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