MP 2.1 Internal RAID seems slow

Discussion in 'Mac Pro' started by Trimster, Aug 1, 2016.

  1. Trimster macrumors newbie

    Joined:
    Nov 1, 2015
    #1
    So I have 2 x 1TB 7200 RMP drives (WDC WD1001FALS-00J7B1) Which rate fairly high in the pile of similar drives. Blackmagic speed test gives a single drive a 106 MB/s write and 102 MB/s read. Array them together (internal bays 3 & 4) and I get 194 MB/s. Somehow that just seems slow when the SSD boot drive I have comes in at 250MB/s. It would seem to me that the RAID should come close if not exceed the single SSD.

    I'm doing video editing and color correction and feel the real need for some speed here. Are these numbers all I can expect from a couple of spinning disks internally?

    TIA
    Bob
     
  2. h9826790 macrumors G4

    h9826790

    Joined:
    Apr 3, 2014
    Location:
    Hong Kong
    #2
    You simply have the wrong concept.

    Your benchmark is reassuring the sequential speed. (A single large file read / write speed).

    And system boot up require high random small files read /write performance.

    However, there is no relationship between this 2 areas. A HDD can have very good max sequential speed, but extremely poor random 4k speed. That's why we need SSD.

    If fact, for most home users, the benefit of using SSD is the high IOPS (e.g. 100,000 IOPS), but not the max sequential speed (e.g. 1500MB/s). For system boot up, as long as the SSD has high IOPS, they can perform roughly the same. (e.g. a 850Evo which installed via the native SATA 2 port, which limited to 250MB/s, can boot in about 20s. And a PCIe SSD that has 1500MB/s installed in the same machine, can also just boot up in about 20s.)
     
  3. Trimster thread starter macrumors newbie

    Joined:
    Nov 1, 2015
    #3
    So, thinking out loud... If I installed a PCI card that's SATA 3, the drives connected to that controller would allow the SSD to run at full speed (or close)? Something like the cards that allow one to install 2 SSDs on the card and then RAID those?
    Bob
     
  4. h9826790 macrumors G4

    h9826790

    Joined:
    Apr 3, 2014
    Location:
    Hong Kong
    #4
    Like a Sonnet Tempo SSD Pro. That will much much faster than your current setting (in both sequential and random read/write). Sequential may be 4x faster, but random can easily >10x faster (real world result, theoretical can be >100x faster).

    However, since the PCIe card itself is very expensive. It make more sense to get a relative expensive PCIe SSD which has even higher performance, but a very very low cost adaptor. Unless you are looking for something like >1T SSD storage, then SATA option may be still significantly cheaper.
     

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