Re: RMAN backup validate
Date: Sun, 15 Mar 2015 01:12:04 -0400
Message-ID: <550514A4.9050206_at_yahoo.com>
On 03/15/2015 12:13 AM, MARK BRINSMEAD wrote:
> Hmmm.
>
> "SAN Snapshots". These are *great*, when used properly. And I am
> sure that Mladen does.
Thanks.
>
> These things scare me some, though, because some people don't seem to
> understand that some (most?) SAN snapshots -- the ones that are
> described as "near instantaneous" -- aren't REALLY "backups" until you
> COPY the data to another volume. (And if you have a "smart" SAN array
> with de-dupe technology, that may mean copying to an entirely
> different array.)
I agree. On NetApp, the copy mechanism is usually SnapVault or sometimes
SnapMirror. On EMC, it's SRDF. The idea is the same: to copy snapshot
to another filer or array. Another good trick is to have a proxy
instance which mounts the snapshot and does rman backup of the snapshot.
Most modern utilities like Avamar or Simpana have such abiiity. There
are even specialized snapshot based solutions like Delphix or ActifIO
which can copy snapshot to cloud
>
> If you don't make a copy (and ensure it is not "de-duped") then there
> is a good chance that your "snapshot" is still dependent on the
> physical integrity of the original data/storage. Lose the disks
> holding the original data, and you lose the snapshot, too. This is
> not always going to be the case, of course (every vendor's offering is
> different), but it will probably be the case a lot of the time.
>
>
Yes, that is of course true. If the original array is lost, as some were
during the hurricane Sandy, all the snapshots will also be lost, unless
copied to a different array.. As for the deduplication databases (aka
DDB), those are usually local to SAN, as relying on the remote DDB would
be both too slow and unreliable. Most of the modern DDB vendors like
CommVault, EMC, NetApp or Quantum require local SSD to be used for DDB.
However. if the local DDB does get corrupted, then there is trouble and
the deduplicated backups will likely be unusable. I don't know about
other manufacturers, but Commvault does provide both backup and recovery
for deduplication databases. I have never seen a backup being unusable
because of deduplication database being lost.
Details like that are private property of each vendor. Details about
Commvault deduplication are available on
http://documentation.commvault.com. If someone is interested, this would
be a good place to start:
http://documentation.commvault.com/commvault/v10/article?p=features/deduplication/c_deduplication_overview.htm
-- Mladen Gogala Oracle DBA http://mgogala.freehostia.com -- http://www.freelists.org/webpage/oracle-lReceived on Sun Mar 15 2015 - 06:12:04 CET