NBU 7.x synthetic backup guidelines
We are into the design phase for a project where we expect the combined filesystems on a single RHEL5.3 box to be around 28TB. The estimate is about 90k files ranging from 0-100GB each (all old mainframe data converted from EBCDIC to ASCII on open systems). We also think there will be around 100GB of changes per day (not every day, but some). Is using synthetic backups still viable with 100GB of changes a day or was it really designed for small offices, or primarily static data? We wont have alot of this data on a system to test this for some time so just trying to see how valid a solution it might be.
Initially we will have to take it all to tape unless we get a dedupe device in place before all 28TB gets moved in there. We'll have a bunch of LUNs on the SAN that make up the Veritas disk groups, so would off host backups be better than messing with synthetics? Or would PureDisk be the way to go?
The 7.0 admin guide for UNIX seems to indicate that large change rates are not good candidates for synthetics, but what constitutes "large"? Is it a TB per incremental? or 10GB or what? 100GB out of 28TB is not much, but we just don't get the vagueness of the recommendations in there.
thanks all ahead of time!
Dave
Comments
the "classic" synthetic full
the "classic" synthetic full will copy the last full backup and put all the changes from the incrementals into that. so the last full backup, the incrementals and the new full backup should all reside on a disk for this to work. tape with all the positions and mounts will take a lot of extra time. for a 28 tb server a synthetic full will probably take days - i don't think this is what you want.
then there is the optimized synthetic. this works with media server deduplication and does practically the same, but doesn't move all the data around, it just sets pointers on the old data and so you will get the new full backup really fast. this is the option i'd prefer.
of course you can to with off-host-backup or san media server. you might get better speed for the full recovery of the 28 tb system with this way, but this depends on the tape and disk speed. single file recovery will be faster with disk backup.
Thanks for the info. I've
Thanks for the info. I've heard of the optimized synthetic option but we have no dedupe device as the target yet, guess I'll have to read up on that.
For the time being, we are going to just mount up snapshots and see how painful that is.
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