Some Advice on Buying NAS

Recently, we have seen a big increase in the number of Network Attached Storage (NAS) appliances being bought by research projects within the School of Informatics. The attraction is easy to see: at face value, they offer considerably cheaper storage than any of the other storage options available (for a rundown of these options, see Data storage options). But before going for the cheap and cheerful approach, there are a number of factors you should consider.

• You may not get as much for your money as you think.
  Your box comes with 4 2TB disks - so that's 8TB of storage for your precious data, right? Well, only if you are happy about the prospect of all of your precious data being lost if one of the disks in your box fails. To protect against disk failure, you need some sort of redundancy - probably RAID5 or (if you are really concerned about reliability or performance) RAID10. With RAID5, one disk in the RAID set is used for parity to enable any failed disk to be rebuilt. That's a quarter of your storage gone before you start! With RAID10, where each disk is mirrored, you lose half your storage! So bear in mind that when speccing up your box, you may need more disks than you bargained for. Storage bought from the School or Information Services is of course all based on RAID disks. When you buy 4TB, 4TB is what you get.

• The storage may not be as reliable as you are used to
  When specifying one of these devices, it's always tempting to populate it with disks at the lower end of the price range. Unfortunately, you may well find that this low price is reflected in the disk's reliability means that it is all the more important to use some form of RAID to protect against disk failure. But as mentioned above,this will eat into the amount of storage you actually get from your box. Of course you can always opt for a more enterprise oriented model of disk but you may well find in this case that your storage is looking considerably more expensive than it once did.

• Where is this box going to go?
  You may think that your new hardware will be able to go into the self-managed server room. But unless your new kit can be rack mounted, and you have already agreed this with computing staff, there's no place in the self managed room for it to go. Even if it can be installed in a rack, space in the self managed server room is always at a premium and there is simply no guarantee that a space in a rack can be found. If that's the case, you may be faced with the prospect of your new storage having to sit on your desk or in the corner of your office. Depending on the amount of noise and heat your new kit pumps out and the amount of network bandwidth it take up, this may make you less than popular with your office mates. Note also that if said office mates are in the habit of leaving the office unlocked when they pop out for a coffee, then your precious data will be at the mercy of any passer-by - which leads us to the subject of...

• Security
  The security of sensitive data is something which is of great concern to the University. If the data you are storing on your new appliance is in any way sensitive, then you must ensure that either (and preferably both) your storage is in a secure location (i.e. not your office) and sufficiently robustly encrypted to prevent others being able to access the data on the device, even with unfettered access. Be sure your new purchase can support this before parting with the cash. There is more information about securing your data here.

We realise that research grants are not limitless and that sometime a cheap NAS box may be the only way to get the storage your project needs. But be aware that all such purchases must be made through our procurement officers, and that in most cases they will ask one of the computing staff to get in touch to make sure that this will be an appropriate purchase. You can get in touch with the procurement team via the computing support form at https://www.inf.ed.ac.uk/systems/support/form/. You can use the same form to seek the advice of the computing staff before making your purchase and we would strongly advise you to do so.