Performance guidelines for individual HDD/SSDs?

Question

I really appreciate all the great computer building and system guideline information here in the hardware forum, but I've not found a thread which explains desirable individual hard drive and SSD performance characteristics, and how they pertain to video editing needs.
For example, people seem to talk mostly about sequential read/write performance...but is that the only data we really need to consider when shopping for drives? CrystalDiskMark tests sequential, 512K, 4K, and 4KQD32. Does stellar 4k performance matter? If a drive manufacturer breathlessly proclaims 50,000 IOPS performance, what's that going to do for me?  In short, it would be great to know which benchmarks are useful for us, and why.
It would also be helpful to understand optimal task assignment based on performance information. I thought I had read one should use the fastest individual drive for previews...or was it for scratch disc? And I assumed the recommendation pertained to drives other than C:, but I hate to assume. And what type of "fastest" are we talking about?
Note: I asked this question in the generic disk setup guidelines thread and was advised to start a new thread for it.

Answer 1

These are all valid questions, but OTOH it may be you are oversearching in your quest for information. However to start with a site that delivers or better said, that used to deliver very valuable information about all kinds of disks, look here: http://www.storagereview.com/
Lately their performance database seems to be rather out of date and very few new entries in the last year or so, but still very informative.
The much touted IOPS for some SSD's are irrelevant for video editors. They are mainly useful if you have high transaction websites that need to access high volumes of very small files. Examples are news sites, webshops, etc.
What is relevant for video editors? Generally it is about storing and accessing large files, even when one shoots short clips in the range of 3 or 4 seconds, but especially if one shoots longer clips, say interviews, wildlife, sceneries, live performances, etc. So for video editors sequential transfer rates are far more important than IOPS.
Once the clips are ingested, they need to be easily accessible for sequential reading, but to add to that are the much smaller indexed, conformed and peak files that are stored in the media cache with pointer files in the media cache database and for these files random access times are more important than sequential transfer rates.
However, people tend to forget that even more important than benchmark scores in various tests, fill rates can completely undo any advantage of a marginally faster disk. A disk that shows better benchmark performance than any other disk will in practice be slower than many other disks if its fill rate increases more than other disks. Say you have a disk that is a top performer with a capacity of 750 GB and you have a mediocre performing disk with a capacity of 2000 GB. In practice when you have 400+ GB stored on both disks, the smaller one is already showing performance degradation and the larger one is still going strong.
The best way to improve performance on an editing rig is to increase the number of disks, to lower the fill rates and to expand raids to more disks. Expanding raids (notice the R, so I do not suggest this for aid0 because of the lack of redundancy) means that the performance of the raid controller will get more impact on the system and may be of bigger importance than the choice of the hard disk.
If I were to build a new system today, I would have a serious look at the Hitachi 7K3000 series of disks, for instance the 2 or 3 TB models. Price/GB is very attractive, around € 0.045 per GB, performance is great and their reliability is reputed to be great and no longer deserve the 'Deathstar' name. With those disk sizes, you will keep fill rates low and not suffer performance degradation, even with large amounts of data stored. Imagine a 16 disk raid30/50 with two hot-spares and a net storage capacity of 24 TB (using 2 TB models) or 36 TB (using 3 TB models) and you will be hard pressed to fill that to notice any performance degradation and you will easily have a sustained transfer rate of more than 1000 MB/s if you have a good controller.