Which side (of an hdd) is hotter? - Page 1
Forum section: electronics / general

author: Rick Law
author_rank: Super Contributor
timestamp: February 18, 2019, 11:08:22 pm
content: I was about to re-mount a bunch of disc drives in an array. A thought hits me. Is the component side of an HDD the hotter side of the drive, or the other side (top of the aluminum enclosure)?I don't have the tool to measure temperature well. On an un-powered drive, I found my cheap IR temperature reader is impacted by the relative reflectivity too much for me to trust the data.Thinking out loud: My gut feel is, the component side is the hotter side. The moving air created by platters spinning at 7200RPM could create quite a bit of heat. That heat (total power consumed by the motor) is distributed to the whole enclosure. The component side (total power consumed by the PCB) is "added heat" undistributed by the good heat conducting aluminum case. That should behave like a hot plate sitting on top (or below) the case - hence my gut feel on that side being hotter. But I don't know that for sure... Just gut feel.Anyone has real data on that?

author: ogden
author_rank: Super Contributor
timestamp: February 18, 2019, 11:32:26 pm
content: You are right that hottest spots are on the PCB. HDDs always shall have forced airflow from both sides anyway, so it is not that important which side is hottest.https://www.servethehome.com/thermal-imaging-western-digital-4tb-nas-options/

author: Mr. Scram
author_rank: Super Contributor
timestamp: February 18, 2019, 11:37:29 pm
content: Quote from: ogden on February 18, 2019, 11:32:26 pmHDDs definitely don't always have airflow across them, and I don't think its as required as airflow over something like the motherboard. The latter will often get you in trouble when it's missing.

author: ogden
author_rank: Super Contributor
timestamp: February 18, 2019, 11:52:18 pm
content: Quote from: Mr. Scram on February 18, 2019, 11:37:29 pmIncrease of HDD temperature by 15C increases HDD failure rateapproximately two times. If you want to play roulette with your data - you are welcome to overheat your HDD's.

author: nctnico
author_rank: Super Contributor
timestamp: February 18, 2019, 11:59:06 pm
content: Quote from: Mr. Scram on February 18, 2019, 11:37:29 pmThey should if you want HDDs to last long. In better quality PCs they always make sure the HDDs get some airflow. It can mean the difference between failing within 2 years or still running after 10 years.

author: Mr. Scram
author_rank: Super Contributor
timestamp: February 18, 2019, 11:59:53 pm
content: Quote from: ogden on February 18, 2019, 11:52:18 pmWhat's your source? Google says there isn't, Microsoft says there is and Backblaze says there isn't. Besides, 15 degrees Celcius probably means locking the drive away in a tight enclosure or with little airflow or even convection. There's a huge difference between forced airflow being required, allowing proper convection or restricting all airflow."After looking at data on over 34,000 drives, I found that overall there is no correlation between temperature and failure rate. To check correlations, I used the point-biserial correlation coefficient on drive average temperatures and whether drives failed or not. The result ranges from -1 to 1, with 0 being no correlation, and 1 meaning hot drives always fail. Correlation of Temperature and Failure: 0.0"https://www.backblaze.com/blog/hard-drive-temperature-does-it-matter/

author: nctnico
author_rank: Super Contributor
timestamp: February 19, 2019, 12:04:49 am
content: Quote from: Mr. Scram on February 18, 2019, 11:59:53 pmBut these drives aren't running very hot. In a standard ATX case you'll see much higher temperatures. As a rule of thumb every 10 degrees increase in temperature (over 25 degrees) means the MTBF gets halved. At 30 degrees you won't see any effects indeed.At better test would be to run drives at 40, 50 and 60 degrees Celsius and see how long they last on average.

author: IanB
author_rank: Super Contributor
timestamp: February 19, 2019, 12:05:44 am
content: Quote from: Mr. Scram on February 18, 2019, 11:37:29 pm(Most) HDD's absolutely need proper cooling arrangements. I discovered this the hard way when I tried to upgrade the disk in my compact case PC with higher performance ones (tried two different brands). The disk mounting has little airspace around it and no air flow from the case fan. The new disks overheated, faulted and shut down the PC. The only disks that work in that slot are low power "eco" disks with a low thermal load designed for unventilated enclosures.

author: Mr. Scram
author_rank: Super Contributor
timestamp: February 19, 2019, 12:10:43 am
content: Quote from: IanB on February 19, 2019, 12:05:44 amSee my post above. Completely blocking any airflow including ambient convection is probably a bad idea. Even small amounts of energy compound into high temperatures when there's little to no energy transfer.That being said, I've never seen drives fail due to temperature or even heard of it outside of your experience. I'm certainly not saying it's not possible as there isn't any reason it wouldn't be, but it does seem to require slightly unusual conditions. We stick drives into tiny portable enclosures and that seems to work out okay.

author: ogden
author_rank: Super Contributor
timestamp: February 19, 2019, 12:20:36 am
content: Quote from: Mr. Scram on February 18, 2019, 11:59:53 pmGoogle research I mentioned, and not only. Compare 35oC and 50oC failures, they show around 2x failure rate. Backblaze "research" is joke because max temperature is around 30oC which is withinrecommendedoperating temperature range. 45oC and above shall be considered as "too hot" HDD. This indeed means mounting error or fan failure/absence.

author: Mr. Scram
author_rank: Super Contributor
timestamp: February 19, 2019, 12:30:55 am
content: Quote from: ogden on February 19, 2019, 12:20:36 amI hadn't seen you linking to that document, as the link was edited into the post after I quoted it. I did refer to that document in my previous post. I guess it proves my point. A hard drive without forced airflow won't easily reach 45 degrees Celsius without being in a severely airflow restricted scenario. You don't just need the absence of forced airflow, but also an additional restrictive scenario or high ambient temperatures. Note that forced airflow in a hot case can actually worsen things, as hot air can continually be forced over a drive.

author: ogden
author_rank: Super Contributor
timestamp: February 19, 2019, 01:02:15 am
content: Quote from: Mr. Scram on February 19, 2019, 12:30:55 amAnyway here it is:https://static.googleusercontent.com/media/research.google.com/en//archive/disk_failures.pdfQuoteAll you need - missing fans for minitower case and hi-performance (>=7200 RPM) HDD or better two. I have plenty of experience to say so.

author: nick_d
author_rank: Regular Contributor
timestamp: February 19, 2019, 01:06:00 am
content: I can confirm that HDDs are prone to failure when mounted close together.I had two 3.5" drives in the 19mm height form factor, I created a custom enclosure for them with 2mm airspace above and below the drive pair and 2mm in between the drives. I did this because it's a home NAS and the motherboard required only 45mm including the fan, so it would have been a shame to waste space inside the enclosure by mounting the drives at the standard 25.4mm spacing rather than my 21mm spacing.I thought that convection within these 2mm air spaces would naturally cool the drives, but in fact they've both failed within a year. I wasn't super confident of the drives in the first place, one of them could have had an intermittent fault before, but both of them? It's probably the heat.For my next attempt I will use the taller 25mm drives, I was going to mount them at the standard 25.4mm spacing with a hole in the case for the top drive to protrude and everything else kept the same... but now I'm wondering if I need to provide more airspace or forced airflow? Hmm.cheers, Nick

author: Mr. Scram
author_rank: Super Contributor
timestamp: February 19, 2019, 01:20:08 am
content: Quote from: ogden on February 19, 2019, 01:02:15 amThe exact interior of that minitower is probably quite relevant to the result. I have some experience with convection cooled HDDs and they don't seem to go anywhere near the 45 degrees Celsius limit. I'd recommend some airflow if possible, but convection cooling is not nearly as worrisome as restrictive cases.

author: Mr. Scram
author_rank: Super Contributor
timestamp: February 19, 2019, 01:23:40 am
content: Quote from: nick_d on February 19, 2019, 01:06:00 amWhen two or more drives are mounted together, the vibrational interaction of the drives can apparently start playing a significant role.

author: rdl
author_rank: Super Contributor
timestamp: February 19, 2019, 02:46:09 am
content: Quote from: Rick Law on February 18, 2019, 11:08:22 pmIf you can mount them vertically instead of horizontal, it won't matter too much. If you're cramming a bunch of fast, hot drives into a small space and they will all be in constant use, then you still need good ventilation.

author: Rick Law
author_rank: Super Contributor
timestamp: February 19, 2019, 03:23:49 am
content: Thanks guys, this is interesting discussion..Quote from: rdl on February 19, 2019, 02:46:09 amActually, my server with my home video has the drives mounted vertical for that exact reason - I was not sure which side was hotter (even back a decade ago, that was on my mind but not enough for me to spend too much bio-CPU on thinking about that), besides, my vertical setup gives me better air-flow so I mounted it vertical and let it be. That set up has been running for over a decade with 3/4 of the drive around 10 years old!My workstation has drives mounted horizontally. With a couple of dead-drives on my work-station, I am reallocating a couple of those server drives to my workstation (replacing them with faster/more-cache versions.) So, the which-side-hotter mind-puzzler came back into mind.The interesting info in this thread is, well, interesting... This gives me a rule of thumb - I am setting (targeting) 40/50C as high-temperature-limit.