It really is all over the board as to the details... Think of it as a custom filesystem with a really large block size. (As in 64 or 256 MB instead of the typical 8K you see in a normal filesystem.)
As to how the whole deduplication thing works, you can read an article I wrote on the subject here: http://tinyurl.com/3588fb --- W. Curtis Preston Author of O'Reilly's Backup & Recovery and Using SANs and NAS VP Data Protection GlassHouse Technologies -----Original Message----- From: ADSM: Dist Stor Manager [mailto:[EMAIL PROTECTED] On Behalf Of Steven Harris Sent: Monday, June 11, 2007 4:31 PM To: [email protected] Subject: [ADSM-L] Just how does a VTL work? Allen S. Rout wrote: > This is irrational to some extent, I recognize. But for the VTL, I > don't know where the database is; it's _magic_. > > - Allen S. Rout > Good point Allen, I realize that VTLs come in different flavours from several manufacturers, but is there any information about how their gizzards are arranged? I'd particularly like to understand how tape blocks are mapped to disk blocks, and how the de-dup technology is organized. There are a number of possible implementations, and I can see that DB searches/updates could become an enormous bottleneck particularly in a windows environment with potentially thousands of identical copies of windows system files. This raises the spectre of another proprietary database to be managed, grown, reorganized and re-indexed with limited facilities. Does anyone have pointers to this sort of information or is it a deep, dark commercial secret? Thanks Steve Steven Harris AIX and TSM Administrator Brisbane Australia Moving to Sydney Mid July - Offer me a job now and avoid the rush!
