In the classic 1956 movie, “Invasion of the Body Snatchers” (see the Wikipedia entry below if you’ve never seen or heard of it) the conclusion is left open – for the viewer to decide. That’s part of what makes it so great.

http://en.wikipedia.org/wiki/Invasion_of_the_Body_Snatchers

Now, I can hear you saying…”how the heck is Peglar going to tie that into storage?” Well, work with me here…and let’s look at how the industry is moving. I strongly believe that the 2.5″ disc drive is going to ‘take over the world’ for rotating storage in the not-so-distant future. So, I ask you to look around at your own storage infrastructure, your storage vendor(s) and their roadmap, and see how 2.5″ drives are going to fit into your world…because they are coming, and like the Pod People, you can’t stop them!

The entire idea of using 2.5″ drives in the enterprise has been anathema for many years. Enterprise 2.5″ drives have been around for several years, but vendors never designed arrays to use them, because they not only wouldn’t but couldn’t – they were too small, too fast and too unpredictable. Too small both in terms of physical design (a “disk shelf” wasn’t designed for them) and logical design, i.e. capacity. Too fast in terms of being able to control the physical vibration that ensues, especially for 15K RPM drives, in the drive enclosures they chose to OEM. Too unpredictable in terms of reliability, since most arrays don’t perform any sort of managed reliability – which is critical for 2.5″ drives, even more so than for their 3.5″ predecessors.

Enter the ISE. The ISE was designed with the 2.5″ drives fully in mind. Today, one can have 40 enterprise 2.5″ drives in a 3U container, with full managed reliability and self-healing. The benefits to performance-starved applications are many – but perhaps the best benefit of all is the lack of having to, as a human, deal with herding and managing all these small creatures. This is why no enterprise array vendor except Xiotech has architected the 2.5″ drives into a fully-baked architecture. For others, like the pod people, they are just impossible to control, especially in arbitrated loops.

But the big news of 2.5″ drives is this – the upcoming capacities of these drives are rapidly expanding. Soon, you will see 300, 450 and even 600 GB per drive at 10K RPM, and 15K RPM is being developed as well. Further out, you will see 900 GB and beyond per 2.5″ drive, as bit density improves. These drives, when packaged correctly – as in the ISE – will provide not only a quantum leap in IOPS but a leap in capacity per U – which is a Hobson’s choice today.

I say that because one can certainly package 2TB 3.5″ drives (5400 RPM, SATA, 10^14 BER) in an enclosure, and some vendors are doing just that. However, these drives are extremely difficult to manage in practice – if you think rebuilding a 1TB 7200 drive is fun, you haven’t seen anything yet – and also suffer from poor data integrity, since SATA drives cannot perform DIF and have poor UER compared to their capacity. One colleague at Xiotech, a very senior engineer, correctly said “these drives are a data error waiting to happen.”

The Hobson’s choice is trading off reliability, manageability and human interaction for sheer physical density. It’s a poor choice either way. Having said that, let’s be very clear – 10^15 BER 3.5″ 2TB SATA drives exist, but the storage array vendors aren’t using this technology, going instead for the cheaper route. It’s a net loss for users, truth be told.

This is where the 2.5″ drives really take over. Since they are much smaller physically, the drives/U ratio is superior to the 3.5″ variety, and over time the TB/U ratio will be superior as well. The BER is already superior at 10^16.

So, when you look at what architectures are going to win (take over?) in the future, look at the 2.5″ drives. Like the pod people, they will not be able to be stopped…but the ending is open. The good news is that the ending for us in storage is a happy ending, perhaps unlike the movie. One thing is for certain, though; the disc drive is at once shrinking physically and growing logically, and that’s a movie worth paying for in the theater of storage.