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



Jeff Sturm wrote:
-----Original Message-----
From: linux-cluster-bounces redhat com
[mailto:linux-cluster-bounces 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


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