Our snapshots are to be more exact "copy on new write" as opposed to "copy on old write", with the advantage of no penalty at all in terms of performance of taking the snapshot, and performance of filesystem after taking it (think of "copy on old write" - filesystem needs to read old block, write it in the backup location, then write the new block in old place - that's 3 I/Os. For us it's only 1). We do not have to go back to specific locations on the disk, and that's a real advantage in terms of performance.
In regards to full compared to snapshot - with NetApp, it's probably always better to backup snapshots, as they are point-in-time - when you've started your backup at 19:00, all of it will be consistent to 19:00 sharp, unlike traditional backup, which data changes while you backup... So - if you get me right - you can even do full backup from a snapshot...
On Legato - I think you can just mention .snapshot/hourly.0 for example in your path of backup. If you use NDMP, you anyway backup a snapshot, as the filer's dump creates one automatically for you.
Hope it somewhat helps, Eyal.
---------------------------------------------------------------------- eTraitel - I'm the new eBuzzword around !!! ---------------------------------------------------------------------- Eyal Traitel - Filer Escalation Engineer CNA, MCSE, CSA, LCA, NetApp CA
Network Appliance BV Holland Office Center Kruisweg 799b 2132 NG, Hoofddorp The Netherlands Office: +31 23 567 9685 Cellular: +31 6 5497 2568 Email: eyal@netapp.com ---------------------------------------------------------------------- Get answers NOW! - NetApp On the Web - http://now.netapp.com ----------------------------------------------------------------------
-----Original Message----- From: E.J. Jantz [mailto:ej_jantz@bswintl.com] Sent: Wednesday, April 25, 2001 3:55 PM To: toasters@mathworks.com; simon_clawson@mentorg.com Subject: Re: snapshot backup
just a question: If the 'snapshots are "copy on writes' doesn't that mean that a backup of .snapshot is equal to and functions as a full backup? If not, can Legato using a NFS mount on a unix server capture just the info the .snapshot uses? If so, how?
thanks...
EJ Jantz, IST Dept. BSW International One West Third, Ste 100 Tulsa, OK 74103-3505 918 582-8771 ej_jantz@bswintl.com 918 295-4166 918 587-3594 fax
"Clawson, Simon" simon_clawson@mentorg.com 4/25/01 4:32:08 AM
Is it possible to backup just the .snapshot and then perform a restore from this data?
I am looking for ways to speed up the backups and this seems to be a possible option. It was suggested to me by a colleague as a method of backing up Clearcase VOBS, but would it be viable for the whole filer. Of course I would need to run a full backup at tleast once a month, but this would help me speed up most of my weekly runs.
Any ideas/suggestions/views?
Simon
Simon Clawson HDS Team Systems Administrator Mentor Graphics Uk Rivergate London Road Newbury Berkshire RG14 2QB <<Clawson, Simon.vcf>>
On Wed, Apr 25, 2001 at 08:28:39AM -0700, Traitel, Eyal wrote:
Our snapshots are to be more exact "copy on new write" as opposed to "copy on old write", with the advantage of no penalty at all in terms of performance of taking the snapshot, and performance of filesystem after taking it (think of "copy on old write" - filesystem needs to read old block, write it in the backup location, then write the new block in old place - that's 3 I/Os. For us it's only 1). We do not have to go back to specific locations on the disk, and that's a real advantage in terms of performance.
In regards to full compared to snapshot - with NetApp, it's probably always better to backup snapshots, as they are point-in-time - when you've started your backup at 19:00, all of it will be consistent to 19:00 sharp, unlike traditional backup, which data changes while you backup... So - if you get me right - you can even do full backup from a snapshot...
There's one potential problem - if your backup does not finish in time between 2 snapshots, they will rotate (say, hourly.0 will become hourly.1, and the new hourly.0 has started) , so in the end you're backing up not what you started backing up. For scheduled backups one should be cautious to, for example, do a full backup from weekly.0 and incremental one from nightly.0, but if you're doing a on-the-fly dump, always keep your snapshot schedule in mind.
Igor
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Igor Schein -
Traitel, Eyal