On Wed, Apr 30, 2008 at 6:36 PM, Mike Sparkes <[EMAIL PROTECTED]> wrote:
> Multiplexing mixes streams of data from multiple sources into one stream > to the storage device. A de-duplication product on that storage device will > be breaking up the stream into blocks and looking for duplicate blocks. Let > us assume that three backups are being multiplexed and that no data changed > since the previous backup. It is unlikely that the data will mix together > again at the same rate in the same ratios to create the same blocks and so > they will be treated as unique and stored in full. > I disagree. Multiplexing doesn't mix up the blocks coming from each server. You may see things like block 1 and 2 from server 1 followed by blocks 1, 2, and 3 from server 2, but if block 2 from server 1 is the same as block 3 from server 2, it will de-dupe. It doesn't matter what the speed is today versus yesterday - you're not de-duping the tape but you're de-duping the blocks. Duplication typically is not done by files - it's done by blocks, and that isn't changing with multiplexing. .../Ed Mike Sparkes > > > ------------------------------ > > *From:* Ed Wilts [mailto:[EMAIL PROTECTED] > *Sent:* Wednesday, April 30, 2008 4:12 PM > *To:* Mike Sparkes > *Cc:* veritas-bu@mailman.eng.auburn.edu > *Subject:* Re: [Veritas-bu] Multiplexing on VTLs > > > > On Wed, Apr 30, 2008 at 5:58 PM, Mike Sparkes <[EMAIL PROTECTED]> > wrote: > > if you ever move > to de-duplication, the act of multiplexing your backups ruins the > ability to detect duplicate blocks. Your de-dupe ratio will be terrible. > > > I don't follow your logic here. Why would multiplexing affect the de-dupe > ratio? > -- Ed Wilts, Mounds View, MN, USA RHCE, BCFP, BCSD, SCSP mailto:[EMAIL PROTECTED] If I've helped you, please make a donation to my favorite charity at http://firstgiving.com/edwilts
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