Monday, 5 March 2007

Backing Up Branches

I've spent the last few weeks being heavily involved in a storage performance issue. Unfortunately I can't discuss the details as they're too sensitive (in fact, I can't even mention the TLA vendor in question), however it did make me think more about how we validate a storage architecture design will actually work.

As part of another piece of work I'm doing, I have been looking at getting branch or remote office data into core datacentre infrastructure, the premise being not to write tapes in remote locations and therefore be at risk of compromising personal information.

I've looked at a number of solutions, including the Symantec/Veritas PureDisk option (the flashy flash demo can be found here). What strikes me with this and other solutions is the lack of focus on data restores and meeting RTO and RPOs for applications that may run in branch locations. In fact, I think most products are aimed at the remote office which runs a small Windows implementation and therefore isn't worried too much about recovery time of their data.

The technologies such as PureDisk work by reducing the data flowing into the core datacentres, either by de-duplication, compression or both technologies. This is fine if (a) your data profile meets their view of compression (b) your applications/data produce a small percentage of changed data on a daily basis. Unfortunately for some applications this just doesn't occur. In addition, if you lose the site (or even easier, corrupt or lose the local metadata database) then you're looking at a total restore from core to recover an entire server. These solutions work on the basis that branch offices have low WAN bandwidth and the backup tools utilise this by making a small pipe appear as a much larger pipe through the aforementioned de-dupe and compression. This doesn't help if a full restore needs to be performed.

Some people may say "but you could manage the restore by sending a tape to the site containing the last backup" - however that defeats the original objective of keeping tapes out of the branch.
I'd like to see some real-world examples from Symantec/Veritas showing how long backup/restores would take with their product. Of course they're not going to provide that as it would immediately highlight the issues involved. Perhaps we need an independent backup testing lab to do that comparison for all backup products on the market.

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