Assuming no snapshots. Do full backups (ie. tar or cpio) eliminate the need for a scrub? Thanks, Chris -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://mail.opensolaris.org/pipermail/zfs-discuss/attachments/20100308/8ecbb95b/attachment.html>
On Mon, 8 Mar 2010, Chris Banal wrote:> Assuming no snapshots. Do full backups (ie. tar or cpio) eliminate > the need for a scrub?No. A scrub verifies correctness of all the metadata and file data. A backup will only read (and verify) only as much as is required for the backup. Besides failing to verify redundant copies, the backup will fail to verify data which is retained by snapshots. The backup will also fail to verify disk data which is already cached in RAM. Regardless, a successful backup goes a long way toward providing assurance that the filesystem is working correctly. Bob -- Bob Friesenhahn bfriesen at simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/ GraphicsMagick Maintainer, http://www.GraphicsMagick.org/
On 08 March, 2010 - Chris Banal sent me these 0,8K bytes:> Assuming no snapshots. Do full backups (ie. tar or cpio) eliminate the need > for a scrub?No, it won''t read redundant copies of the data, which a scrub will. /Tomas -- Tomas ?gren, stric at acc.umu.se, http://www.acc.umu.se/~stric/ |- Student at Computing Science, University of Ume? `- Sysadmin at {cs,acc}.umu.se
-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 On 08.03.2010 21:08, Chris Banal wrote:> Assuming no snapshots. Do full backups (ie. tar or cpio) eliminate the > need for a scrub? > > Thanks, > Chris > > > > _______________________________________________ > zfs-discuss mailing list > zfs-discuss at opensolaris.org > http://mail.opensolaris.org/mailman/listinfo/zfs-discussAs far as I can see: No. They perform different things. If my manual-reading-skills are up to scratch, scrub protects you against latent fs errors and bit rot (thus: Making sure the data on the disks is correct). Backups copy whatever data is on the disks, even if that data itself is faulty. Again, this is my opinion based on my man-page-reading-skills (which hasn''t always been good). Kind of like making a photocopy of a document doesn''t replace proofreading the first one. //Svein - -- - --------+-------------------+------------------------------- /"\ |Svein Skogen | svein at d80.iso100.no \ / |Solberg ?stli 9 | PGP Key: 0xE5E76831 X |2020 Skedsmokorset | svein at jernhuset.no / \ |Norway | PGP Key: 0xCE96CE13 | | svein at stillbilde.net ascii | | PGP Key: 0x58CD33B6 ribbon |System Admin | svein-listmail at stillbilde.net Campaign|stillbilde.net | PGP Key: 0x22D494A4 +-------------------+------------------------------- |msn messenger: | Mobile Phone: +47 907 03 575 |svein at jernhuset.no | RIPE handle: SS16503-RIPE - --------+-------------------+------------------------------- If you really are in a hurry, mail me at svein-mobile at stillbilde.net This mailbox goes directly to my cellphone and is checked even when I''m not in front of my computer. - ------------------------------------------------------------ Picture Gallery: https://gallery.stillbilde.net/v/svein/ - ------------------------------------------------------------ -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.12 (MingW32) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/ iEYEARECAAYFAkuVWo0ACgkQSBMQn1jNM7ZAEgCfdoqTIaN2+g8HwHog6/vw5QDJ mVEAoIPzOsZL0mEqa7Q7bP9+j7+47K/l =JSVQ -----END PGP SIGNATURE-----
On 08/03/2010 20:08, Chris Banal wrote:> Assuming no snapshots. Do full backups (ie. tar or cpio) eliminate the > need for a scrub? >No. The reason is that a full backup will use ARC caches and won''t read all copies of each block if pool is redundant. SCRUB assures that all data and all its copies are read and validated. -- Robert Milkowski http://milek.blogspot.com
On Mon, 8 Mar 2010, Svein Skogen wrote:> correct). Backups copy whatever data is on the disks, even if that data > itself is faulty.Zfs does validate data when it is read from the disk so the only way that the data itself can be faulty is if it becomes corrupted in RAM after being read and checksummed. Bob -- Bob Friesenhahn bfriesen at simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/ GraphicsMagick Maintainer, http://www.GraphicsMagick.org/