I thought we DID address that in one of the posts. (Maybe I'm getting things confused with another thread I'm having on the same topic.)
A properly designed de-duplication backup system should restore the data at the same speed as, if not faster than the backup, and the tests that I've done with a few of them have all worked this way. I believe it's something you should test, but it appears that the designers thought of this natural objection and designed around it. I believe it has to do with the fact that restoring 100 random pieces to create a single file means you get to read off of a bunch of spindles. I will say that there are speed differences between the de-dupe appliances (VTLs) and de-dupe backup software. De-dupe backup software still restores fast enough for what it was designed for. (You should be able to fill a GbE pipe with such a restore.) But they're not going to restore at the 100s of MB/s that you can get out of one of the appliances. --- W. Curtis Preston Backup Blog @ www.backupcentral.com VP Data Protection, GlassHouse Technologies -----Original Message----- From: ADSM: Dist Stor Manager [mailto:[EMAIL PROTECTED] On Behalf Of Richard Sims Sent: Friday, August 31, 2007 3:13 PM To: [email protected] Subject: Re: [ADSM-L] Data Deduplication On Aug 31, 2007, at 4:33 PM, Dave Mussulman wrote: > ... Avamar said their software got > 10-20% reduction on a backup of a stock Windows XP installation. A > single system, say it's the first one you added to your backup group. > That's not two users with the same email attachments saved, or > identical > files across two systems - that's hashing files in the OS (I presume > from headers in DLLs and such.) ... I'm mildly amused that in all these postings on the subject, none has addressed the corollary of the backups: restoral. There are likely some implications in the restoral of files backed up this way, perhaps most particularly in system files; and restoral performance is also something one would wonder about. And there may be situations where such a backup/restore regimen is to be avoided, because of issues. Perhaps those with experience in this area would post what they've found. Richard Sims, at Boston University
