Re: Linux LVM software raid, and SAN question.

On Jan 23, 4:36 pm, Kyle Schmitt <kyleaschm...@xxxxxxxxx> wrote:
....
So it appears to be that it's not standard having the db server handle
the mirroring across the sans.
OK, fair enough.
But, to get to the core of it... in linux would this best be done via
LVM mirroring, or software raid (level 1)?

Since you seem to be stuck with this architecture and these are your
only two options, I would use LVM.
The software raid stuff has really been designed to provide raid
capabilities for people who couldn't afford a raid controller or
storage array.
It likes to think of storage as disks, and it's only goal in life is
to protect against catastrophic disk failure.
You on the other hand, have luns coming from storage arrays via HBAs
over two dual-redundant SANs. I'd like to think you certainly
don't have to worry about disk failures anymore, since there shouldn't
be any single point of failure left, other than perhaps power outage
taking out an entire array.

At least with lvm, you get to attach and detach the luns from the
second array as you see fit (for example if you want to take down the
2nd array for maintenance)
And with lvm, maybe you can even wow your boss by making a snapshot on
those luns, providing some logical snapshot taken at strategical
points in time, rather than a blind mirror.
Note that without using enterprise-level software (read: $$$) which
would allow you to integrate the snapshot into the database, you'll
need to manually coordinate flushing and freezing the db
before taking a snapshot at the volume manager level.
.

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