In an earlier posting, I discussed protecting data on the “edge” of your network. I mentioned how it’s one thing to create a policy that employees only keep critical data on your centralized servers and storage, but it’s another thing entirely to make that type of policy work. However, since this has previously been discussed, let’s move on to other reasons that you want to ensure flexibility in supporting heterogeneous storage: DAS (Direct Attached Storage), NAS (Network Attached Storage), and SAN (Storage Attached Network).
DAS is simply the storage that you put in your server. Everyone supports DAS. Well – wait a minute. Not everyone. SAN vendors don’t support DAS. But that doesn’t make sense, does it? After all, SAN vendors are storage vendors – not backup vendors – right? Well…it’s complicated. SAN vendors often talk about snapshots and replication with and without virtualization to make the case that they can offer data protection. And in some cases they can. Buying two SANs and placing them at different data centers does offer replication – which enables some elements of data protection, albeit at a very high price in terms of SANs and the bandwidth between the data centers. SAN snapshots allow logical copies of data to be made – they work as long as the SAN operates and you don’t have worms or viruses permeating the data.
But SANs are famous for something called the “SAN island.” This is when a SAN vendor sells a top-to-bottom storage and backup solution, which makes the customer “locked in” to that solution. At that point, if you see an advertisement for $89 for a 7200RPM 3.5” one terabyte disk drive and decide to put it in your server, you’re screwed – because your backup “solution” (the SAN) doesn’t protect anything except the SAN (and that includes both DAS and NAS). Our friend above visited SAN island and had trouble escaping.
Buyers with NAS devices simply need to make sure that the NAS is supported by the backup product they plan to use. There are different levels of protection – from client-based backup to direct forms of backup, including both mount and NDMP approaches.