Written by W. Curtis Preston
Friday, 16 February 2007 15:57
Up until just a few months ago, it was cheaper to just buy some random cheap disk and back up to it. VTLs were more expensive for two reasons: the existence of de-dupe and the fact that some software vendors are now charging you to back up to regular disk.
I was just talking to a customer the other day who believes that VTLs cost too much and they're not worth the extra cost. It got me to thinking: is that really true anymore? The answer's no.
Here's the facts:
| | ATA Disk Array | De-duped
disk or VTL
| Comments |
Per/TB hardware cost
| $3-8K | $1K | Best attempt at street prices of low end disk.
All de-dupe vendors are coming out at about $1/GB
|
| Per/TB backup s/w license | $0-1K | $0-1K | Disk: Legato $1K/TB, Symantec $0 (for now), TSM $0
VTL: Legato is per slot, Symantec $1K/TB, TSM, $0
(TSM's prices already include storage devices.)
|
| Total cost per TB | $3-9K | $1-2K | |
Please stop telling me that VTLs are more expensive than regular disk. I return you to your regularly scheduled web page.
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thank u!!
Now for the sake of arguement:
1) For an environment that is considering possible back up to disk prior to going to tape, how does the VTL cost compare to tape (including disks, tapes, library, VTL device itself, etc)?
2) What if that company already has a SAN in place with enterprise class storage arrays? Would it be more cost-efficient to add storage to existing arrays or look into purchasing a new VTL? Assume that the existing arrays are already being maintained by the storage group. There are maintenance procedures in place. Also, consider power requirements and floor space (expanding existing arrays Vs. purchasing a new VTL)
3) I guess I'm not clear on what exact advantages a VTL can offer that you can not get from plain disk? My understanding is that VTL's imitate tape or makes itself look like tape to the software (due to some limitations), however now-a-days most enterprise backup softwares have worked out those limitations so there is no longer a need for it to look like tape to the software. Am I correct? Then what is value in VTL's?
I know a lot depends on individual requirements (and environments), but a good thourough comparison would be interesting to see.
From what I've seen, intelligent disk keeps the advantages of disk based backup (simultanious read/write w/ NetWorker, etc...), while not increasing complexity any more than many other solutions.
Thanks,
Aaron
And, no. I haven't seen any unbiased shootouts.
As to the advantages and disadvantages of each, I've written quite a bit on that. You should be able to find quite a bit out there. (Of course, it's covered in detail in my new book, Backup & Recovery. Sorry, shameless plug.)
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