The snapshot disk space only needs to hold the amount of the changed data - not the whole filesystem. To the applications, it appears that a copy was made, but actually writes are being held behind the scenes. Don't think I'm explaining this well (Monday am), so lets try an example. Say that the UV DB is 10GB and it will take 1 hour to back it up. During 1 hour, only 1GB of data will be changed. The snapshot LV needs to be 1GB + a little for overhead - not 10GB. If you do a df while snapshot'ed it appears that 2 10GB partitions are mounted - the original and the snapshot. But the snapshot LV is actually only holding the pending writes. Unmounting the snapshot writes all the data (in order) to the real LV. While snapshot'ed the OS knows what's changed and what hasn't and UV never knows the difference. Robert F. Porter, MCSE, CCNA, ZCE, OCP-Java Lead Sr. Programmer / Analyst Laboratory Information Services Ochsner Health System This transmission (including any attachments) may contain confidential information, privileged material (including material protected by the solicitor-client or other applicable privileges), or constitute non-public information. Any use of this information by anyone other than the intended recipient is prohibited. If you have received this transmission in error, please immediately reply to the sender and delete this information from your system. Use, dissemination, distribution, or reproduction of this transmission by unintended recipients is not authorized and may be unlawful.
>>> "[email protected]" <[email protected]> 8/20/2011 1:13 PM >>> We don't mirror but we use filesystem snapshotting for a clean backup with less than 10 seconds of downtime: ... Only cost in this is enough disk for snapshot. Jeff Butera Sent from my iPhone _______________________________________________ U2-Users mailing list [email protected] http://listserver.u2ug.org/mailman/listinfo/u2-users
