zeigh
Level 1 (8 points)
Desktops

Q: Best Use of Speed- At the Startup or Data Volume?

Hello,

 

Sorry for such an elementary tech question but, which volume needs to be the fastest in an efficient workflow; the startup volume or the data volume? I never really thought about it like this before...

 

I am reconfiguring an older Mac Pro with SSD via PCIe capability for the startup volume. Two SSD’s in a RAID 0 configuration blaze along at 900 MB/sec. However, a single receiving SATA III hard drive is averaging only 200 MB/sec because of the hardware limitation of the hard drive bay. So, where is the speed needed the most; doing the work or writing/storing the work? My next option is to create a RAID 0 volume of four hard drives, but I still need to understand the basics first.


Yup, there are allot of variables. If it makes any difference, the primary focus is for video editing and the heavy rendering involved.

 

 

Peace,

Dr. Z.

Mac Pro, OS X El Capitan (10.11.6), null

Posted on Sep 8, 2016 3:47 PM

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zeigh

Q: Best Use of Speed- At the Startup or Data Volume?

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  • by Kappy,

    Kappy Kappy Sep 8, 2016 3:58 PM in response to zeigh
    Level 10 (270,418 points)
    Desktops
    Sep 8, 2016 3:58 PM in response to zeigh

    The volume most frequently used and accessed.

  • by Grant Bennet-Alder,

    Grant Bennet-Alder Grant Bennet-Alder Sep 8, 2016 6:38 PM in response to zeigh
    Level 9 (60,774 points)
    Desktops
    Sep 8, 2016 6:38 PM in response to zeigh

    Your notion of the speedup provided by RAID is overly simplistic. RAID gets its speedup with Rotating Drives on the second and subsequent Read (or Write) from the Same large file. This is because you do not have to endure the dead time while the second drive seeks, it is overlapped with the previous Read (or Write) from the Same file. If you are not Reading (or Writing) to the same large file, there is no speedup from a RAID. But you DO still endure the complexity of a RAID.

     

    The speedup happens in the same way for the second and subsequent Read (or Write) from a large file on an SSD RAID, but the savings is FAR smaller, because the latency is already very low -- there is little to save.

     

    When you Read or Write randomly, or read (or Write) small files, RAID does not produce any savings at all.

     

    The best way to get the fastest speeds is to use your fastest drive for the boot drive. You will not see much real benefit from RAIDing it. The System is always "snacking" from the Boot drive, doing small random reads and writes of parts of your User-ID, parts of Applications and Libraries, parts of Directories, parts of Paging files, parts of Preference files, and other similar things.

     

    If you are doing Video editing the best performance is obtained by having Source files on one drive, Destination files on another drive, Scratch files (if used) on another drive, and the Boot drive separate. Dedicating those same drive to a huge RAID makes no sense, because you are not using them in the way that a RAID provides a speedup -- Reading (or Writing) from the SAME large file.