ADSM-L

[ADSM-L] Using NDMP backups to migrate from one Celerra to another

2009-03-18 19:47:45
Subject: [ADSM-L] Using NDMP backups to migrate from one Celerra to another
From: "Schneider, John" <John.Schneider AT MERCY DOT NET>
To: ADSM-L AT VM.MARIST DOT EDU
Date: Wed, 18 Mar 2009 18:39:53 -0500
Greetings,
    Our Storage Team is migrating all filesystems from one Celerra NAS
to another.  Today we backup the old one via NDMP, and are beginning to
backup filesystems on the new one via NDMP as they come online.
    The Storage Team would like to use the NDMP backups as a way to
migrate the large amounts of data to the new NAS filesystems.  The
Storage Team has decided that they don't like using utilities like
Robocopy or Rainfinity.  They experimented with both, and because of the
millions of small files involved, both would take a long time and
adversely affect the performance of the NAS filesystems involved.  
    The strategy using the NDMP backups would be:
 
1) Take a backup for a filesystem on OLDNAS, and restore it to a
different filesystem name on NEWNAS. 
2) Once the restore is completed, use Robocopy or such utility to keep
the two filesystems in sync with changes that are still happening on the
filesystem on OLDNAS.
3) On the day of the cutover, stop all traffic to the filesystem, use
Robocopy to sync one last time
4) Switch the NAS mappings over to the new filesystem on NEWNAS.
5) Start doing NDMP backups to new filesystem on NEWNAS.
6) Repeat for every filesystem that needs to be migrated.
 
Sounds easy enough, but I can't figure out any practical way to restore
an NDMP backup from OLDNAS to NEWNAS.  The Restore Node command doesn't
provide a way to redirect the backup data to another NAS.
Theoretically, I could update the TSM NDMP definition for OLDNAS to
refer to NEWNAS, then when I do the Restore Node it would restore the
data to NEWNAS.  I would also have to update the Tape path definitions
so they are correct for NEWNAS. (I have not actually tried this.)  But
in practice that means that for the duration of the restore I can't do
any NDMP backups or restores for OLDNAS.  If it were a small filesystem
I could be sure of restoring in a few hours, that would be OK.  But the
whole reason we are doing this is because of some multiple TB
filesystems that will not restore in a few hours.  Today one of them
takes 18 hours to backup, and we have never tried restoring it.   That
could take a couple days, and we can't go that long without backup.  Or
at least we don't want to.
 
Any brilliant ideas on how to accomplish this?  Is there a way to
restore NDMP backups created on one Celerra to another without
disrupting everything? Or should I not even be trying?  :-)
 

Best Regards,

John D. Schneider 
Lead Systems Administrator - Storage 
Sisters of Mercy Health Systems 
3637 South Geyer Road 
St. Louis, MO  63127 
Phone: 314-364-3150 
Cell: 314-750-8721 
Email:  John.Schneider AT Mercy DOT net

 
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