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I have some huge files that I have to parse to produce even bigger files, and 2 discs in my machine, one SSD and one HDD.

I was wondering what would be the fastest way to process those files : I guess it would be best to read from one disk and to write on the other, but would you rather read from SSD or HDD ? Or maybe since SSD is faster, it could be best to do everything on it ?

I am looking not only for advice for this particular case, but also for any kind of file processing activity where you intensively read AND write to disk, like compressing files, converting video, etc.

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Try it and see. –  Daniel Andersson Apr 27 '12 at 13:01
    
@DanielAndersson : I will, but it will be a bit long, and it will be biased by the perfs of my specific drives. I wanted to know if there was general advices for this. –  Zonko Apr 27 '12 at 14:55
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5 Answers

up vote 2 down vote accepted

In general, SDD have a better performance about the reading part of your process than the HDD. And, in general, your SDD might have be used before, so there might not be enough "clean areas" to be written without having to perform some kind of erase first.

If you can't test to see which combination is faster, try reading from SDD and writing to HDD.

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It seams you had the right answer, but it was contradictory with the other ones, so I couldn't tell. –  Zonko May 2 '12 at 15:47
    
I don't agree with this answer. SSDs are typically significantly faster than HDDs at both reads and writes - especially for random reads and writes. (There can be exceptions for sequential accesses - see here for an example.) Also, the point about "clean areas" is largely irrelevant if TRIM is being used. –  sblair May 2 '12 at 15:58
    
@sblair I think the OP made some tests and confirmed it... and TRIM is a very good action, but can't save everything if your saving large files without giving enought time to it happen. –  woliveirajr May 2 '12 at 16:13
    
@sblair indeed, I chose this answer after making the tests myself, and the link you provide sustains the answer if I read well. Of course, my tests can be biased by the fact that I have a pretty fast HDD. –  Zonko May 2 '12 at 16:37
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Considering the fact that an SSD is capable of much greater read/write speed than a conventional mechanical HDD, logic dictates that any task which relies on read and write speed would be better achieved using an SSD. Things to consider are obviously the size of the files (and the resultant files) and the size of the SSD.

If your SSD is relatively new, then there is a good chance it will have trim. In which case, then the 'erasing' mentioned in the other answer is rendered obsolete as this takes care of keeping the disk clean.

My suggestion would be, if you have enough storage space on the SSD, use it.

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I made some benchmarks myself, here is the setup :

  • SSD : Intel, 80Go, 69% free
  • HDD : WD Velociraptor 160Go / 10k rpm, 79% free

I am reading a 1Go file and adding info to each line, producing a 3Go file, using a batch writen in C# using StreamReader/StreamWriter.

And here are the results :

R    W     times in seconds                    average
SSD  SSD   79   77   78   77                   78
SSD  HDD   67   62   70   68                   68
HDD  SSD   100  113  85   74   118  68   81    91
HDD  HDD   81   81   70   80                   78

So, as always when I do benchmarks, I'm über confused by the results, especially the speed of the HDD to HDD process, and the dispersion of the HDD to SSD process (that's why I made more measures for this one).

Clearly, it's better (at least on my configuration) to read on SSD and write on HDD. If someone has an explanation for the results, I'm all ears.

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Well, my edit was disconsidered, so... –  woliveirajr May 2 '12 at 17:46
    
can you edit your own answer to add details maybe ? –  Zonko May 3 '12 at 8:13
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It depends on the file sizes. If you are dealing with smaller files, such as 4kB-256kB or so, the SSD will perform better than the HDD, if you are working with lots of files simultaneously.

If you are working with large files, sequentially, like say video files, the HDD will be better, depending on capacity. Typically higher capacity results in higher sequential read and write, due to platter density increasing, and in turn requiring less movement from the head. If your HDD is less than 750GB in capacity and NOT made within the last 3 or so years, the SSD will probably beat the HDD out in every facet except for capacity.

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SSD is the best option for anything. Whatever you might want to do with it. SSD's are very, very fast...probably ten times faster...no, not kidding, it really is that fast. So, whatever you want to do on your computer, use a Solid State Drive.

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