Re: [Xen-users] Alternatives to a dual-primary DRBD setup

[Bart Coninckx <bart.coninckx@xxxxxxxxxx>]

On 05/20/11 20:51, Daniel Meszaros wrote:
> Hi there,
>
> usually I am just lurking around here collecting ideas about issues 
> that I could run into in the future but now it seems my time has come 
> to ask for your help...
> Until now I ran a Citrix Xenserver 5.6 on a dual-primary DRBD setup. 
> But for any reason I am experiencing sync problems now, maybe due to 
> the raised I/O load (setup without guest machines, now ten virtual 
> servers).
> I am tapping a bit in darkness at searching for the needle in the 
> haystack causing the problems. Therefore I am thinking about possible 
> alternatives that allow useful things like XenMotion but possibly at a 
> lower performance usage level.
> My current setup:
> - two servers with dual 12-core Opterons and 32 GB RAM, each
> - each server equipped with a 500 MB (hardware) RAID1 for the host and 
> with a 14 TB (hardware) RAID5 for the guests that's being replicated 
> using DRBD
> - each server with a 10 GbE NIC
> - Citrix Xenserver 5.6, both running in one pool
>
> What are your ideas? Is it worth thinking about other storage solutions?
>
> CU,
> Mészi.
>
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To me it sounds your setup should be fine. It does depends on the nature 
of your guests of course. 10 is not a lot though.
I would try to find the bottleneck:

- do an effective measurement of the DRBD link with netperf
- investigate none of your guests is swapping heavily consuming a lot of I/O
- investigate your disk performance. RAID5 is not ideal, more striping 
would be better.
I don't think you're very likely to have better performance with other 
setups, like iSCSI.
.B


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