[Linux-cluster] Cluster with shared storage on low budget

[Gordan Bobic]

Jeff Sturm wrote:
>> -----Original Message-----
>> From: linux-cluster-bounces at redhat.com
> [mailto:linux-cluster-bounces at redhat.com]
>> On Behalf Of Gordan Bobic
>> Sent: Tuesday, February 15, 2011 7:05 AM
>>
>> Volume resizing is, IMO, over-rated and unnecessary in most cases,
> except where data
>> growth is quite mind-boggling (in which case you won't be using MySQL
> anyway).
> 
> We actually resize volumes often.  Some of our storage volumes have 30
> LUNs or more.  We have so many because we've virtualized most of our
> infrastructure, and some of the hosts are single-purpose hosts.
> 
> We don't want to allocate too more storage in advance, simply because
> it's easier to grow than to shrink.  Stop the host, grow the volume,
> e2fsck/resize2fs, start up and go.  Much nicer than increasing disk
> capacity on physical hosts.

Seems labour and downtime intensive to me. Maybe I'm just used to 
environments where that is an unacceptable tradeoff vs. £40/TB for storage.

Not to mention that it makes you totally reliant on SAN level 
redundancy, which I also generally deem unacceptable except on very high 
end SANs that have mirroring features.

Additionally, considering you can self-build a multi-TB iSCSI SAN for a 
few hundred £/$/€ which will have volume growing ability (use sparse 
files for iSCSI volumes and write a byte to a greater offset), I cannot 
really see any justification whatsoever for using LVM with SAN based 
storage.

> Haven't tried DRBD yet but I'm really tempted... it sounds like it has
> come a long way since its modest beginnings.

Not sure how far back you are talking about but I have been using it in 
production in both active-active and active-passive configurations since 
at least 2007 with no problems. From the usage point of view, the 
changes have been negligible.

Gordan