Tanha, Part 2

Subtitle: Maybe more than you wanted to know

For most of a year, I was gallivanting around, spending lunch hours at various stores, lusting after new furniture, scheming with sketchpads and spreadsheets to get a server cabinet design. Meanwhile, back at the house, our server at the time was far from healthy.  Backups weren’t happening, hardware was throwing errors, all of the 118 Henry Street photos, documents, records in danger of loss by disk drive failure.

Over the Xmas/New Year holiday just past, we spent several days getting things stable again. Yet, despite my aching desire to ignore the server function, so I could obsess about the server form, the computer that is the center of our digital life never really got better. In fact, 3 of the 5 hard drives were ready to fail at any time.

We had already had one server crash during my period of infatuation with Tibetan server cabinets, I was determined to not risk another. By February, 2011, all efforts were about a new piece of server hardware.

Hard drives are motorized, spinning mechanical “platters” of magnetic metal with sensor “heads”. On these magnetic platters is all of your data stored in a computer. The platters spin at about 7500RPM in most newer hard drives. The heads that read and write your data are suspended within 40 nanometers (that’s about 0.00000001 inch) of the spinning platters. The angular forces on the sensor arms can reach over 500G’s.

Hard drive internals showing platters and sensor arms, courtesy of Wikipedia

For those of you who didn’t know about hard drives, and, for sure, those of you already bored with this discussion, you must remember one thing:

 Hard drives are the single most common, most frequent failure of a computer.

They are subject to very high mechanical stresses that are magnified by wear, heat, and vibration.

It’s not a question of “if it will fail”, it’s simply a question of “when will it fail”.

Knowing, intellectually, professionally, and experientially, about the whole “hard drive failure” thingy scares the daylights out of me. So, we set about designing a server for maximum MTBF (Mean Time Between Failures) of the hard drives.

Hard drives, you see, come in 2 popular flavors: the 3.5” flavor, found in almost all desktop computers. And, the 2.5” flavor, found in all portable and laptop computers.

The inches correspond to the diameter of the platters, courtesy of DigitalDingus.com

I say “flavors” instead of “sizes” because the two types are designed for very different working environments. The 3.5” drive is designed for maximum performance and storage capacity in a physically stable environment without regard to power consumption. The 2.5” drive is designed to be used in an unstable physical environment (think “rugged”) and to consume less power (think “battery) at the expense of speed and capacity.

If, as was mine, the goal is hard drive maximum MTBF, it makes sense to put cool running, rugged, low power consuming 2.5” drives in a stable physical environment. A stable environment found, conveniently enough, next to my desk at 118 Henry Street.

For those readers not asleep, and possibly even interested in this topic; most of the technical research that I did is very succinctly and simply summarized in this article at DigitalDingus.com concerning 2.5” vs. 3.5” hard drives.

I leave you, fair reader, to extrapolate from this discussion the importance of data backups on your individual computer.

By “backups”, I mean, 2 or more copies of your data, on different hard drives, regularly synchronized.

(Addendum:  Couple of good comments came in via email concerning solid state hard drives (SSD). I did purposefully leave those out of the hard drive technology discussion. Simply put, they are not quite mainstream yet. With prices about $2/Gb, compared to $0.25/Gb for mechanical drives, and the not-completely-solved issues related to defragmentation, storing large amounts of data on SSD is not happening at this time. For example, with my server project, we have 4Tb of storage, that would be something south of $8000 in SSD hard drives compared to about $550 for mechanical drives.)