RE: new database server build - sanity check

From: Patterson, Joel <>
Date: Wed, 30 Jan 2013 14:04:28 -0500
Message-ID: <>

Answer Ryan and Chris at same time.

This a Solaris ZFS feature.

The source of the differences... As per my sysadmin: "No difference really.. the algorithm is pretty much the same.. Some databases (Oracle, MySQL) support ZFS snapshots while the database is up. Its called a "crash-consistent" backup.. In other words, the snapshot saves the database in a state as if the database server lost power and crashed. Most vendors design their software to recover from this type of event".

A 'clone' can be created from a snapshot which can be run separately, however you would want to change the database name and probably filenames if the filenames incorporate the db name in the path.

The clone has to remain tied to the snapshot, so the clone would have to be copied off to another system, but you can just do that with RMAN. In fact if the 'other' system can create a soft link to your RMAN backup area, then no copying is necessary and RMAN can just duplicate the database using that backup.

Joel Patterson
Database Administrator
904 727-2546

-----Original Message-----
From: Ryan January [] Sent: Wednesday, January 30, 2013 10:04 AM To: Patterson, Joel
Cc:; Subject: Re: new database server build - sanity check

I had no idea that the Solaris snapshots were treated differently. Do you happen to know the source of the differences? Is this a feature of Oracle on Solaris, ZFS, or a combination of both?

I 100% agree on using snapshots for testing. Outside of the database they also work great for binary patching. It's a very quick and simple rollback in the event of unforeseen issues.

On 01/30/2013 07:45 AM, Patterson, Joel wrote:
> Your points are well taken, and of course I would never advocate relying on a snapshot for production backups. One would of course have oracle RMAN backups available at all times. The snapshot capability is so that you can try something, and if you don't like it, put it back quickly and in a matter of minutes. If you snapshot for whatever reason is gone, you still have the old fashioned restore. The Solaris snapshot can be taken with the database up -- and there is no need for backup mode etc.
> That is what I meant by nice feature. It is just a another option in the arsenal of tools.
> Joel Patterson
> Database Administrator
> 904 727-2546
> -----Original Message-----
> From: Ryan January []
> Sent: Tuesday, January 29, 2013 6:15 PM
> To:
> Cc: Patterson, Joel;
> Subject: Re: new database server build - sanity check
> I would never trust a snapshot as a sole means of backup. They still allow for single points of failure. Backups are all about redundancy; something that snapshots do not inherently provide.
> As an example: if you have a storage (SAN, RAID Controller, or disk) failure your "backup" was on the same media as your primary storage.
> You've potentially lost your database.
> As long as you're aware of the restrictions/penalties which come along with snapshots they can be wonderful tools used in an overall backup or DR strategy.
> The snapshot can be seen as a point in time copy of the filesystem. As
> such, you would treat the database as you would for any database backup
> at the filesystem level. If the database is open you would put it in
> backup mode, snap the file system, then end backup mode. Creating a live database from the snapshot would also be similar to recovering a database from a file system level backup.
> While this process technically doesn't require additional software, it's a relatively time intensive process. If this happens on a regularly you
> will want it automated. This lends itself to another great excuse for
> backup/recovery testing.
> I happened to run across a related article yesterday. It's mostly an rman sales speech, but does bring up some valid points.
> fra-snapshot-322251.html
> On 01/29/2013 12:02 PM, Chris King wrote:
>> Sounds like ZFS snapshots could be a good backup or even a DR strategy? Is extra/specific software required to take/use snapshots for live/open Oracle databases? Or does the database have to be closed to do this?
>> **
>> The snapshot capabilities can be a nice feature. You can snap a live
>> database and restore it back
>> within moments -- eliminating the time needed for an RMAN restore.
>> Having said that, I would look into testing some things
>> -- perhaps Google "ZFS evil tuning guide" -- Note however, that there
>> are also websites out there that discount much of what is in the
>> guide, essentially saying to leave the defaults or most of them,
>> hence some testing first. The foundation you lay will be the one you
>> will be using.
>> Joel Patterson
>> Database Administrator
>> 904 727-2546
>> --

Received on Wed Jan 30 2013 - 20:04:28 CET

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