[DRBD-user] Decent shared storage setup for virtualization

James Masson james.masson at lmax.com
Tue Feb 15 11:03:39 CET 2011

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


We built our own setup for similar VM storage workloads, based on a dozen Thecus rackmount SATA
arrays using a custom load of Fedora 12. 1.5Tb Samsung or Seagate SATA disks.

8 disk software raid 10, dual bonded Gig dedicated to DRBD and heartbeat, serving NFS and iSCSI over
Gig.

The hardware/disk/drbd/network combo is just fine - not operating anywhere near it's limits.

In short, don't use linux NFS for VM storage. It does a really poor job of efficiently transmitting
load to the disks. I've spent more than a few weeks trying to tweak NFS clients and server to move
the bottleneck on, but throughput and virtual disk latency over NFS is about 10x worse than what it
is over iSCSI. Perhaps this is also to do with the extra FS layers a NFS hosted VM disk has to
contend with.

We built this as an alternative to NetApp FAS-series arrays, it's way slower at NFS, but broadly
comparable to our Equallogic iSCSI arrays.

Unfortunately, using NFS to manage VMs VMware style is just far more convenient than using 1 iSCSI
LUN per VM.

regards

James M


On 14/02/11 19:59, Dennis Jacobfeuerborn wrote:
> I'm trying to wrap my head around storage setups that might work for virtualization and I wonder if
> people here have experience with creating a drbd setup for this purpose.
> 
> What I am currently planning to implement is this:
> 2 Storage 8-bay nodes with 8gb RAM and a dual-core Xeon processor.
> Each system with gets equipped with 8 1TB SATA drives in a raid-5 configuration.
> Networking will either be two dual-port cards or two quad-core cards which I plan to setup as bonded
> interfaces (balance-xor).
> 
> I'm particularly worried about the networking side being a bottleneck for the setup. I was looking
> into 10gbit and infiniband equipment but they drive the cost up quite a bit and I'm not sure if they
> are necessary if I can bond several 1gbit interfaces.
> 
> Any thoughts?
> 
> Regards,
>   Dennis
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