[DRBD-user] configuring 2 services on 2 hosts

Digimer linux at alteeve.com
Wed Jan 5 19:49:09 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.


On 01/05/2011 11:48 AM, J wrote:
> Hello,
> 
> This is my first go at setting up any HA services, so I wanted to see if
> anyone on the list had a similar setup or any recommendations on doing
> this better using drbd.
> 
> I'm setting up 2 servers with 2 application services on them. One
> application service is postgresql database (about 5GB of data in
> database). The other is custom software that does a lot of file-based
> I/O (about 15GB of files) with a custom TCP server in front of it.
> 
> My idea is to have one server being the master for the custom software
> and the other being the master
> for the postgresql database. The other server will be a stand by for the
> other service. Both will run run ubuntu 10.04 LTS and be connected by 2
> cat6 1Gb cables.
> 
> This will hopefully distribute the load, as I am worried about the
> postgresql clobbering the custom software (which requires very high
> responsiveness).
> 
> So is setting up 2 brbd's in opposite configurations on 2 hosts a good
> idea? I'm mostly worried about
> performance and the headache of admin if the links go down. 2 cases of
> split brain on 2 boxes
> doesn't sound fun at all.
> 
> Thanks!
> J

If you are using platter-based HDDs, then I'd strongly recommend
creating two separate resources on two separate HDD(s). This way you
won't suffer I/O penalties with the read/write heads flying back and forth.

Give your relatively small storage requirements though, I'd even more
highly recommend SSDs providing that the write-cycle limit is within
reason. In this setup, then you should have no trouble running it all on
one resource as there are no heads to flog.

In any case, be sure to have (at least) RAID 1 on each node backing the
DRBD devices to help minimize downtime. Drives fail fairly frequently...
software RAID 1 is an inexpensive route to much better uptime. :)


-- 
Digimer
E-Mail: digimer at alteeve.com
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