[DRBD-user] memory requirements for DRBD

Sam Howard sam.howard at officepcsupport.com
Fri Jan 23 19:05:27 CET 2009

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


How do you serialize the resync?  I don't see the "group" option any more,
which is what I used to control priority and speed of the resync.
I'm on 8.3.0 now, and when I fire up a node that was down, _all_ devices
start syncing, which only makes it take longer due to the underlying disk
thrashing (is my guess).

--Sam

On Fri, Jan 23, 2009 at 10:44 AM, Lars Ellenberg
<lars.ellenberg at linbit.com>wrote:

> On Fri, Jan 23, 2009 at 05:59:47PM +0100, Bruno Voigt wrote:
> > 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 ..
>
> From: Lars Ellenberg
> Subject: Re: Summarizing DRBD memory usage
> Date: 2008-07-24 10:43:52 GMT
> http://thread.gmane.org/gmane.linux.network.drbd/15482/focus=15485
>
> so in your situation,
> right, serialize the resync (probably a good idea anyways).
> and/or maybe decrease "max-buffers", which limits the number of
> in-flight pages.
>
> or give it plenty of ram.
>
> --
> : Lars Ellenberg
> : LINBIT | Your Way to High Availability
> : DRBD/HA support and consulting http://www.linbit.com
>
> DRBD(R) and LINBIT(R) are registered trademarks of LINBIT, Austria.
> __
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