SSDs - are they worth it?

On price per GB certainly not but then what do you use your storage for?

In the enterprise they always talk of tiered storage. You put the disk intensive stuff on the fastest drive you can afford, then the rest goes on something that is reasonably quick but cheap to buy in bulk, then you go for something that is so cheap per GB but slow as wading through porridge where you only put the really old stuff, then there is archive to tape where you are talking minutes/hours or even days to get back to the user.

In old days you had SCSI, IDE and tape, the disk were arrange in to RAID arrays, these stated simply with stripe sets of a few disks and mirrored pairs of disks, then you got redundant disks with raid 5 just in case something failed. Typically a database box would have system on a mirrored pair, Logs on mirrored pair and DB on a raid 5 of 3 or more disks depending on the size of the beast. 

Then along came SANs but these were just glorified storage shelves with the disk arranged in groups of RAID 5 sets and these were then either carved up to different servers or assigned to a single server but each raid set was still normally 6 disks or so then along came systems like the EVA which spread your bit of storage across all the disks in the array. If you were lucky enough to have the money you could have 12 shelves with 14 disks in each shelf that comes to 168 disks, and with FC to the disks there wasn’t much in the way of bottlenecks in getting your data, but it was expensive so this is where you started on tiered stuff and where you start planning your storage usage.

Now we have three types of storage, Solid state, magnetic disks and tape, lots of different types of disk interfaces (SAS, SATA, FC, FATA, SCSI, PATA), lots of ways of grouping it (Raid 0, 1, 5, 6, 10, 50, 60, JBOD) and many ways of accessing it (iSCSI, FC, SAS, NAS, DAS, SCSI, USB, eSATA, Firewire), so tiering is not straight forward needs planning to set up and even more to manage the movement between each tier.

Most of this is irrelevant to the home user, one or two might have gone to the trouble of setting up Raid 0 for the extra performance, but for most it is quite simple, you buy a SATA disk and hook it up, many will use USB or firewire to backup and some will have networked NAS boxes for backups or storing media collections or even online storage over the internet, so the idea of tiered storage is already appearing in the Home.

What has all this got to do with SSDs, well they are blindingly fast compared to hard drives, but they are expensive per GB. You can get a 64GB Crucial C300 for around £90 ($110), for most that wouldn’t actually be of any great use for storing much, but it is enough for your OS, basic files, some important applications, whilst the 1TB disk can store all your lardy games, music, photos etc. This is your tiered storage. Add in that USB or NAS backup drive and you have your three tier storage system just like the enterprise guys.

What will you get from all this? Well keeping your data away from your systems means a rebuild is not quite as bad as it was before, it will also help maintain performance as smaller files systems are faster, the SSD specifically will bring instant launches of applications more like reopening and app from the task bar than actually starting an application, and they will be available as soon as you log on rather than wait for everything to catch up.

What’s the down side? Well SSDs have a limited life span, each cell can only have its state changed 3000 times or so, the bits actually wear out, which equates to around 3 years. With each die shrink, you will get faster writes, but you will get less of them as the physical bit that changes state becomes smaller, unless the technology changes which is the one biggie the industry faces going in to the future. Apart from that there is just the matter of a small hole in your bank balance.