Explanation of the different read/write operations

[Whitestar127]

Hi, could someone provide me with some explanations on the different read/write operations in reviews (for example this: http://www.anandtech.com/show/7173/...w-120gb-250gb-500gb-750gb-1tb-models-tested/8) and the real world applications of those operations?

For example:
When Fraps or some other game recording program writes to the disk, what sort of operation is that? Is it incompressible sequential? This is useful info for me because I'm looking for an SSD which has good write performance for this kind of operation.

What about 4K read/write, in which cases is that used?

Etc etc.

Apologies if this has been clearly answered before.

 

[BrightCandle]

Fraps frametime writes are probably compressible 4k writes although its possible its using a buffer to make it 512k or greater. I don't know which of the two it is but its certain compressible.

Reading and writing large files are obviously sequential. Database access is the classical example of 4k reads/writes and especially high Queue Depth reads/writes. The middle range of 512k is more typical for applications reading and writing files (like game saves and documents).

 

[Whitestar127]

I ran a test in DXtory on how fast it could write to my SSD, which is a Samsung 840 PRO 128GB. I got 315 MB/s (at least I think it was MB/s if I remember correctly) as a result. That's part of the reason why I'm wondering what kind of write operation it is.

So if I use an 128GB EVO can I expect a similar write performance you think (in DXtory that is).

What I'm really interested in is if 128GB EVO or 128GB PRO are fast enough to write really high quality game recordings (uncompressed) at 1920x1080p 60fps using Fraps or DXtory.

Or will I have to get one of the 256GB versions instead?

 

[BrightCandle]

DXTory with video out is definitely sequential in nature, because its writing about 355MB/s of data without any compression (IIRC dxtory does a little better than this with some basic lossless compression in some of its encodings). Most SSDs can cope with that for a while, the key is finding one that can cope with GB's of GBs of writes without showing serious reduction in performance, ie dirty performance.

I did a quick check on reviews and it seems the 128GB copes OK with that but that doesn't mean it will in the real environment of graphical writes sustain it for the length of your recording. You will want to have a look at some quality reviews to see how consistent it is, in spec at least its capable.

 

[Whitestar127]

Thanks for helping