3 Replies Latest reply on Aug 31, 2010 3:06 PM by Harm Millaard

    What difference does 3 drives make instead of 2?

    KenK2468

      Hi all,

       

      I spent quite some time reading all the informative and helpful articles here on this forum with regards to system optimization. I learned a lot about hardware. Thank you.

       

      I just wanted to ask about hard drives for non-professionals / students in video editing.

       

      I understand that it's better to spread around 'read' and 'writes', but wouldn't 2 drives suffice and render the third pointless?

       

      C: OS/Apps/Page

      D: Media / Prev / Export

       

      If you add a third:

       

      C: OS/Apps/Page

      D: Media / Page

      E: Prev/Export

       

      In the 2 drive setup, the application on C: reads from D: and writes to D: - read 1x write 1x

       

      In the 3 drive setup, the application on C: reads from D:, writes to D: (page) and E: - read 1x write 2x

       

      So iwouldn't the 3 drive setup actually be slower?

       

      Since 3 drives are recommended I'm pretty sure I'm wrong, but how would it go faster if the writing has to work 2X instead of 1X ?

        • 1. Re: What difference does 3 drives make instead of 2?
          Harm Millaard Level 7

          You are making some fundamental mistakes here.

           

          There is no difference in the number of R/W activities, since you perform the same actions. The only difference is how you distribute them.

           

          Your two disk example means reading the media files and writing your export files to the same disk and disks can only do one thing at a time. In your three disk example there are the same activities, but one disk for reading and the other for writing.

           

          And your calculus is off. How can the same activities lead to 1x write with only 2 disks and 2x write with 3 disks?

           

          To put it in another way:

           

          One hour of DV material, around 13 GB that needs to be read and written to the same disk means a transfer of 26 GB (13 read and 13 written). Spread it over two disks and each disk only needs to handle 13 GB. Average performance gain close to 50%, disregarding overheads.

          • 2. Re: What difference does 3 drives make instead of 2?
            KenK2468 Level 1

            Thanks for the response.

             

            "...disks can only do one thing at a time" -- this explains a lot. All this time I was thinking hard drives have separate read and write heads.

             

            Cheers

            • 3. Re: What difference does 3 drives make instead of 2?
              Harm Millaard Level 7

              I'm not sure if there ever were separate read and write heads on disks, but it would make the failure rate go up, the cost of the disks skyrocket and the mechanical wear and tear go up, so it makes sense not to do that.