[colug-432] HDD Questions

[Rick Hornsby]

Sent from my iPhone
> On Sep 5, 2016, at 15:50, Thomas Cranston <thomas.w.cranston at gmail.com> wrote:
> 
> I am shopping for 750 GB laptop drive. I have Seagate drive bought in 2013. Manufactured in 2012. SMART reports the drive as OLD, but OK. Smart lists many realigned sector counts. How old is old? Does more GB capacity on drive = more chance of failure?

Drives come with some capacity to remap bad blocks away from failed areas of the disk. They reserve space on the platters (and flash memory in the case of ssd) specifically for this purpose. Does higher GB mean more chance of failure? I think that's unlikely, and I don't think the data I've seen over the years as capacities have increased support higher failure rates. Sure, the data density is higher but more space can be reserved for bad block mapping, as well as the continued improvements in error correction, electronics, materials etc.

> What's different between a 250GB and 750 GB drive, the spinning disk, or the electronics.

Across generations of drive tech that allows larger capacity, yes to both things.

Focusing on two modern drives of the same generation but differing sizes, they're likely physically and electronically the same. A lower capacity drive may just have failed quality checks that would have allowed a larger capacity, or it may be just fine and artificially limited to the lower capacity. Both of these things are common with electronics - video cards are a good example. The difference between two SKUs (and a few hundred $) might be just a few unsoldered traces. I remember this about 3.5" floppy disks specifically (a hole punched into a 720K disk made it a 1.44M disk - though reliability became an issue) but it probably goes back before that.

> I am considering a software type drive. Which have the best reliability? I have heard that the performance is not as good as claimed. Same for reliability.

I'm not sure I even understand what you mean by "software type drive".

> I have used about 25% of the storage capacity of my present drive. Does a lot of unused space over a long period of time lead to problems?

Nope.

On the contrary, IIRC an SSD's performance degrades if the space is over utilized. Most of what I've seen puts it at around > 90%. It has to do with the (computational) expense of returning a marked-deleted NAND block back to the free-to-use pool, and then writing to that newly ready block, vs being able to just write to an already available block.