Yesterday, I was pretty sure I knew what HDD I was going to buy. I was ready to buy 6 new Toshiba 3TB HDD for a ZFS raidz2 array. Then, last night, I decided to do something entirely out of character for people making HDD purchase. I decided to stop reading and start buying.
I decided to buy a single drive of two different types and compare them to each other, and to the drives I already have. I’ll also run these tests on two different machines, in case the hardware makes a difference.
The drives I am buying are:
NOTE: I am providing links to Newegg only because they are good at keeping links that work 3 months down the road.
I will also be testing a Seagate Barracuda ST2000DM001 2TB.
My plan is to test them on two different motherboards, attached to both the motherboard, and to a SATA card.
As just pointed out on IRC, sometimes the differences between two drives are minuscule. Thus, in my opinion, choosing whether to buy brand X or brand Y because one does 5.4ms and the other does 5.5ms should not be as highly rated over say warranty or cost. When it comes to running a ZFS array, slight differences are dwarfed by other filesystem components such as ARC, ZIL, and SLOG devices.
Another valid issue: how does the manufacturer deal with warranty replacements? Some offer cross shipping (we’ll send you a new one now, and you send us that dead one when you’re ready).
Powers of two
ZFS is slightly better in groups of data disks that are a power of two. This is slightly better is terms of space allocation. This isn’t something to be overly concerned about, unless you’re completely off your rocker regarding micro-optimization. Really, we all have much bigger things to be worried about. But you can read about it here and here.
IntelliPark on Western Digital drives
There is some debate about IntelliPark, which parks the head when the disk is idle. However, disks are rated for X parks. Some think you should change the default setting. I found this to be interesting reading, but not something for everyone: http://www.sagaforce.com/~sound/wdantiparkd/.