Re: Backups of Snapshots

From: Alan.McLachlan@didata.com.au
Date: Tue Oct 05 2004 - 00:37:34 EDT

  • Next message: Tim McDonough: "filer MRTG mods to see tape and disk IO, and consistent network io, and larger charts"

    Kevin,

    This isn't what Jack's trying to acheive. However, besides that it's a
    dangerous recommendation.

    Automatic scheduled snapshots are rotated out by their naming convention.
    i.e. "nightly.0" is always last night's midnight snapshot. So, if for some
    reason the backup takes more than 24 hours to write to tape, or is delayed
    by a sheduling issue or a downed drive or whatever, you run the risk of a
    temporally inconsistent backup on tape after the snapshot rotation occurs.
    This might be made obvious by errors occuring because a file that was in
    the original directory map and was deleted during the backup disappear
    from the "nightly.0" snapshot when it's rotated for the next night (the
    previous night becomes "nightly.1").

    i.e. you should always backup using the automatic "snapshot for backup.x"
    created by the NDMP client in Data OnTap, or use a manual snapshot. It is
    never wise to use the built-in scheduled snapshots for anything other than
    point-in-time restores from disk, because their contents will change at
    the next shedule period.

    I agree with your comment about using a static name. But you need both the
    name _and_ the *contents* to remain static, which isn't the case with the
    OnTap sheduled snapshots.

    A manual snapshot is always best for this, i.e. a script like: (using the
    snapshot name "dailybackup"

    rsh filer snap delete dailybackup ;(delete previous manual
    snapshot you've hung on to for restores)
    rsh filer snap create dailybackup
    backup /filer/.snapshot/dailybackup/ ;(or for Windows create a share that
    always points to the root of the snapshot and use that)

    regards,

    Alan McLachlan
    ___________________________________
    Solution Architect - Data Centre Solutions
    Dimension Data Australia
    Alan.McLachlan@didata.com.au
    Tel. +61 (0)2 61225123
    Fax +61 (0)2 62486346
    Mobile 0428 655644

    ----- Forwarded by Alan McLachlan on 05/10/2004 02:20 PM -----

    "Kevin Mascarenhas" <KMascarenhas@syncsort.com>
    Sent by: owner-toasters@mathworks.com
    01/10/2004 11:28 PM
    Please respond to "Kevin Mascarenhas"

     
            To: "Jack Lyons" <jack.lyons@martinagency.com>
            cc: <toasters@mathworks.com>
            Subject: Re: Backups of Snapshots

    Hi Jack,

    One other option you can consider is specifying an existing snapshot as
    your
    NDMP backup source. For example, if you configured your filer to take
    nightly snapshots at say 11:00pm and had your scheduled NDMP backups start
    at sometime after that, then you could configure the backup job to use the
    "nightly.0" snapshot as the backup source. When a snapshot is specified in
    this way, NDMP driven dump will not create another one for backup.

    Any backup software should allow you to define a job that uses an existing
    snapshot (or a snapshot that will exist at the time the job will run) for
    backup. Of course it's simplest if you configure the job to use a static
    snapshot name rather than one which will change each time the job is run
    so
    NetApp scheduled automatic snapshots will work perfectly.

    HTH.

    Kevin

    Kevin Mascarenhas
    KMascarenhas@syncsort.com

    Syncsort Inc.
    50 Tice Blvd.
    Woodcliff Lake, NJ 07677
    Tel: (201) 930-9700
    http://www.syncsort.com

    ----- Original Message -----
    From: "Jack Lyons" <jack.lyons@martinagency.com>
    To: "Paul Galjan" <galjan@gmail.com>
    Cc: <toasters@mathworks.com>
    Sent: Friday, October 01, 2004 6:45 AM
    Subject: Re: Backups of Snapshots

    > I guess that makes sense. it would have been nice to be able to look
    > restore a snapshot directory from 4 months ago!
    >
    > It looks like I could do a monthly snapshot manually and see how much
    space
    > it takes up. Right now, my snapshots are only taking up 23% of the
    space
    > allocated for snapshots. I am going to experiment with taking 6
    "monthly
    > snapshots"
    >
    > Jack
    > ----- Original Message -----
    > From: "Paul Galjan" <galjan@gmail.com>
    > To: "Jack Lyons" <jack.lyons@martinagency.com>
    > Cc: <toasters@mathworks.com>
    > Sent: Thursday, September 30, 2004 7:23 PM
    > Subject: Re: Backups of Snapshots
    >
    >
    > > Hi Jack,
    > >
    > > The snapshot directory is not included as part of the NDMP dump. When
    > > the filer is told to do an NDMP dump, it actually takes a snapshot,
    > > then dumps the data from that snapshot.
    > >
    > > --paul
    > >
    > > On Thu, 30 Sep 2004 18:41:11 -0400, Jack Lyons
    > > <jack.lyons@martinagency.com> wrote:
    > >> I had a user request a file from 4 months ago. The tape backups
    happened
    > >> at
    > >> 11:00 PM but the file they needed was earlier in the day. I was
    thinking
    > >> that the backups might have included the snapshot directory but it
    > >> didn't?
    > >> Is that configurable?
    > >>
    > >> Jack
    > >>
    > >>
    > >
    >

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