On Thu, 2008-07-24 at 11:25 -0700, Collins, Kevin [Beeline] wrote:
> Aren't most people running LVM where you can just add a new LUN, pvcreate and 
> vgextend?  

I'm sure they are, but I believe that's a little bit of a crutch that
Redhat and other Linux developers are using to try to make this seem
less critical.

Most storage arrays make it very easy to simply grow an existing LUN on
the fly and the OS needs to easily support online growth of volumes in
this case.  That other OS from Redmond has supported online growth in
this way since, with the exception of system volumes, since at least
their 2000 version.  It seems a shame that Linux can't do it.

Forcing admins to add LUN's to grow a volume removes from them the
ability to be more conservative and granular with their expansions
because otherwise they end up being forced to manage a large number of
LUN's even with a relatively few systems.  I have a couple of dozens
servers that have been on the SAN for 5+ years.  They've probably had
their volumes grown and average of once a year in that time.  If I
always added a LUN I would now have to manage 125 LUN's just for those
25 servers for no reason other than it's the only way to grow them
online.

It can also significantly complicate the implementation of storage array
based snapshots, especially on some platforms that won't guarantee
consistent snaps across multiple LUN's.  IMO, it's a feature that Linux
really needs.

Later,
Tom


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