[DRBD-user] drdb for hundreds of virtual servers with cheap hardware

Adrien Laurent adrien at modulis.ca
Tue Oct 16 14:40:21 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.

Dear DRDB community,

I need to host reliably hundreds of virtual servers with cheap hardware (ok,
it might not be possible... but I'll give it a shot) and opensource
I've been running in production for over a year about 20 virtual servers on
one machine, but it's not scalable and there is no failover.

I plan to create a reliable NFS NAS with DRDB / heartbeat that will provide
pxe OS to the physical server and data for the virtual server.
Here is a diagram for more details:

I haven't done any setup like this and before I start the implementation of
this solution, I would like to know from your experience if:
-will NFS do the job? (knowing that there will not be simultaneous access of
the same data from different virtual servers). Note: the virtual server will
be relatively small 300Mo each, they will be stored in a folder not an image
(kinda like chroot).
-will Heartbeat "guarantee" that failover his made transparently without
human intervention ?
-My physical virtualization servers will be diskless to simplify management
(only swap will be on a local partition), is it a bad idea - could it
decrease performance ?
-Can DRDB save me the RAID 1 setup ? so that I can use RAID 0 and double my
capacity without affecting nfs service in case of hard disk failure ?
-Has anyone run software RAID 5 and DRDB, or the overhead is too important ?
-A another scenario would be to use the local disk (80Go) of each
virtualization servers (no more pxe or nfs) and have DRDB duplicate the
local disk to a same-size partition on a RAID 5 one server NAS. Do you think
this second scenario would be better in terms of uptime ?

Thanks a lot for any input,


Adrien Laurent
(514) 284-2020 x 202
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