A Few Technical Questions On Hdd's and Cooling Fans

[cornemuse]

I am curious about the 'thickness' of some 2½" hdd's. Mostly they are 8mm thick, some are 12mm. Mostly the older ones are 12mm, though I have newer ones @12mm. Question: does this difference affect reliability/longitivity?
EG: I happen to have an old fat Toshiba ide drive, 12mm, its capacity is 814mb. Yet newer ones 500g/1T are 8mm.

Another, more important question, cooling fans. Mostly, it seems, on cpu fans, air is directed 'down' towards the heat-sink. I accidently broke off one blade of a cooling fan & liked to destroy the works trying to detach the fan from the heat-sink. Wasn't screwed on, but it snapped on with plastic clips, the devil to separate the two. Looking for a replacement fan, (I have dozens of old mobo's, I leave 'em with cpu's & fans attached) I noticed some fans blew air down, but some blew up. It seems to me blowing down towards heat sink makes more sense. The larger case fan on the back of the computer blows out of the case. No fans at the front of the case.

How should fans be 'aimed' on computers? Opinions?

(I could be off on hdd measurements, made quick measures on drives)

[pandy]

General rule is simple - fan is more efficient when it "blow" than "suck" - usually on fan edge you have usually two arrows marks, one shows rotation direction second air stream direction. So try to place fan in such way so it will suck cold air and blow it in heatsink direction. Try to detect and avoid situations where you have two fan installed in a way so they blow in opposite directions as this create place where there is no airflow as opposite air stream nullify itself. Usually best cooling is made by single large fan and produced air stream is directed by air ducts - air channel to distribute air stream in predictable way. Small fans may improve air flow locally. Try also to install air filter on intake - before fan - ideally fan should create inside closed enclosure pressure higher than surrounding air (over pressure) so you can control air quality and avoid distributing dust.

HDD thickness depends on number of plates inside HDD - more plates higher thickness.

[lingyi]

Typical 2.5" HDD drives are 7mm (1 platter), 9.5mm (2 platters), 12mm (3 platters), 15mm (4-5 platters). Each platter is double-sided, so there's two heads, top and bottom for each platter.

In theory, the fewer platters/heads, the less likelihood of failure, but in reality, there's little, if any difference. The reason your old drive is fat, is because it required more, lower density drives to achieve the level of capacity. Here's a blog with lots of info about platter capacity. https://rml527.blogspot.com/

Single platter 2.5" has maxed out at 1TB, and the largest 2.5" HDD is 5 platters = 5TB, and is likely to the end of the line for 2.5" HDD technology as SSDs have taken over the 2.5" form factor space.

Note that with [the exception of] a handful of specialized drives, all 2.5" drives 1TB+ are SMR (Shingled Magnetic Recording). SMR as it's name states, shingles the data tracks like the roof tiles, requiring new data to partially erase and overwrite previous data, causing writes/rewrites to be slower, especially as the drive fills up. Read speed is the same as on [non-]SMR drives.

In general, yes, a fan blowing air across a drive will give better cooling. However, most external hard drive cases and multi-bay enclosures pull air across the drives. But this is because they're designed to draw air in from the front and exhaust out the back. The ideal situation, as found in most PC cases is have both a fan(s) pulling air from the front and a fan(s) exhausting out the back.

[lingyi]

Here's a good article discussing airflow. It's about PC cases, but the theory is the same for all types of cooling. https://www.tomshardware.com/how-to/set-up-pc-case-fans-for-airflow-and-performance

[cornemuse]

Thanx for all info here!
FWIW, This case, and a few others I have, has an opening on side of case with a tube? that go's down (almost) to the cooling fan so outside/cool air is drawn in by fan to heat-sink. As I mentioned : I noticed some fans blew air down, but some blew upwards. ← I allus set so's air is blown towards heat-sink.
Anyways, thanks for all th' info

[pandy]

As I mentioned : I noticed some fans blew air down, but some blew upwards. ← I allus set so's air is blown towards heat-sink.

Create air duct - separate air flows with some stiff, rigid plate like cardboard, paperboard etc - this is easiest way workaround issues with airflow.