backblaze back seagate

In October last year I noted that the Western Digital “Green” drives in my desktop and a new RAID server build looked to be in imminent danger of early failure. That conclusion was based on a worryingly high load-cycle count which a series of posts around the net all attributed to the aggressive head parking features of these drives in order to save energy when not in use. I decided at the time to replace the desktop disk and recycle it to the RAID server. I have since decided to replace the entire RAID array as soon as I can. But which disks to use?

Well, Backblaze, a company which offers “unlimited” on-line backup storage for Mac and Windows users, has just published a rather useful set of statistics on the disks that they use in their storage arrays. The most interesting point is that they use the same domestic grade disks as would be used by you or I rather than the commercial grade ones used in high end RAID systems.

According to the backblaze blog post, at the end of 2013 they had 27,134 consumer-grade drives spinning in their “Storage Pods”. Those disks were mostly Seagate and Hitachi drives, with a (much) lower number of Western Digital also in use. Backblaze said:

Why do we have the drives we have? Basically, we buy the least expensive drives that will work. When a new drive comes on the market that looks like it would work, and the price is good, we test a pod full and see how they perform. The new drives go through initial setup tests, a stress test, and then a couple weeks in production. (A couple of weeks is enough to fill the pod with data.) If things still look good, that drive goes on the buy list. When the price is right, we buy it.

They also noted:

The drives that just don’t work in our environment are Western Digital Green 3TB drives and Seagate LP (low power) 2TB drives. Both of these drives start accumulating errors as soon as they are put into production. We think this is related to vibration. The drives do somewhat better in the new low-vibration Backblaze Storage Pod, but still not well enough.

These drives are designed to be energy-efficient, and spin down aggressively when not in use. In the Backblaze environment, they spin down frequently, and then spin right back up. We think that this causes a lot of wear on the drive.

Apart from the vibration point, I’d say that conclusion was spot-on given the reporting I have seen elsewhere. And the sheer number of drives they have in use gives a good solid statistical base upon which to draw when making future purchasing decisions. Backblaze note that the most reliable drives appear to those made by Hitachi (they get “four nines” of untroubled operation time, while the other brands just get “two nines”) but they also note that the Hitachi drive business was bought by Western Digital around 18 months ago – and WD disks do not seem to perform anywhere near as well as the others in use.

The post concludes:

We are focusing on 4TB drives for new pods. For these, our current favorite is the Seagate Desktop HDD.15 (ST4000DM000). We’ll have to keep an eye on them, though. Historically, Seagate drives have performed well at first, and then had higher failure rates later.

Our other favorite is the Western Digital 3TB Red (WD30EFRX).

We still have to buy smaller drives as replacements for older pods where drives fail. The drives we absolutely won’t buy are Western Digital 3TB Green drives and Seagate 2TB LP drives.

So I guess I’ll be buying more Seagates in future – and I was right to dump the WD caviar green when I did.

(As an aside, I’m not convinced the Backblaze backup model is a good idea, but that is not the point here).

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