Does a greater number of hard drive platter increase the risk of failure?

Question

For example, if you have a 4TB hard drive with one solid 4TB disk (which I do not believe exists yet but that is besides the point), and you have another 4TB hard drive with 4 discs, does the one with 4 discs have a greater chance of failure?

How about 2 platters vs 3 platters? 10 platters? etc.

Update: Now that I know so much more 8 years later, my experience would be that platter numbers isn't as important as other factors like manufacturer and the type of drive. An enterprise-grade drive with 10 platters for example is less likely to fail than a consumer-grade drive with much fewer platters with brand who is known to have a high failure rate.

But it would be nice to see an apples-to-apples comparison, for example, few vs many platters drive from the same manufacturer in the same Enterprise hard drive line and the same technology (e.g. both either CMR or SMR), and both under the exact same loads (same datacenter, same type of server, same temperatures, same humidity, same usage case) to see if the quantity of platters is directly correlated to higher failure.

Answer 1

Backblaze published one of the biggest real-life studies to life expactancies of hdd´s. I looked up the number of platters and the platter capacity for each of the hdd´s they tested (data in Excel format here). I tested the number of platters vs. age and the capacity per platter vs age. Here are the graphs:

My conclusion, (without further statistical testing or conditional probability analysis) is that the number of platters isn't really much of an issue (in this test pupulation), but the platter capacity is. You are better off (in terms of expected age) with more platters and less capacity per platter.

Answer 2

Having less platter means less mechanized parts, so less chance of failure. Consequently it also means less heat and also failure. But the problem is that if you got a failure on a whole platter, you will lose everything.

On the other side, a single platter means much more density, so do speed and access times.

I do personally prefer one platter since it's faster, lighter, but also less failure due to less mechanized parts. I mean, the more you have, the more it will be harder for the heads to spin correctly on the right cylinder, so the more it will easily be aged.

Answer 3

Technically, the parameter of interest should be the number of read/write heads rather than the number of platters.
Typically there would be one R/W head per platter surface. A platter has two surfaces, so if both surfaces are used for data storage, then the number of R/W heads is double the number of platters (for the typical case).
I haven't opened up a HDD in a long time, but in the past I have seen HDDs built with unused surfaces and/or platters. Presumably these were platters that had only one "good" side and installed in a low-capacity model that was otherwise identical to a high-capacity model.

Increasing the number of R/W heads in a HDD is considered a performance benefit, since more data would be in each cylinder and thus can reduce seeks.
The typical tradeoffs for more R/W heads is added cost and reduced reliability (added electronics, more mass to the head actuator) and increased susceptibility to a head crash.

if you have a 4TB hard drive with one solid 4TB disk and you have another 4TB hard drive with 4 discs, does the one with 4 discs have a greater chance of failure?

I would consider a 2-head (single platter) drive to have less chance of failure than a 8-head (4 platter) drive. But (assuming similar areal densities) the 8-head drive should have better random access times.

How about 2 platters vs 3 platters?

Until someone quantifies the increased risk of failure due to the number of R/W heads, you shouldn't base reliability and/or a purchase decision solely on the number of platters and/or R/W heads.