iMac Pro iMac Pro SSD config

Discussion in 'iMac' started by zarf2007, Mar 1, 2018.

  1. zarf2007 macrumors regular

    Aug 27, 2010
    London, UK

    got the base model iMac Pro and looking at other posts was led to believe that the 1TB storage would consist of 2 x 500GB SSD blades in a RAID 0 config. When I check under system information however it appears to be a single 1TB SSD blade.

    Just checking if any other base model owners have the same? doesn't really bother me and tbh would prefer a single blade.

    From system info:

    APPLE SSD AP1024M:

    Capacity: 1 TB (1,000,555,581,440 bytes)

    TRIM Support: Yes

    Model: APPLE SSD AP1024M

    Revision: 114.37.2

    Serial Number: C02747600JKJ803A4

    Link Width: x4

    Link Speed: 8.0 GT/s

    Detachable Drive: No

    BSD Name: disk0

    Partition Map Type: GPT (GUID Partition Table)

    Removable Media: No



    Capacity: 314.6 MB (314,572,800 bytes)

    Available: 298 MB (298,033,152 bytes)

    Writable: Yes

    File System: MS-DOS FAT32

    BSD Name: disk0s1

    Mount Point: /Volumes/firmwaresyncd.p81CkC

    Content: EFI

    Volume UUID: E783267B-A4C3-3556-B751-DBED770EB996


    Capacity: 1 TB (1,000,240,963,584 bytes)

    BSD Name: disk0s2

    Content: Apple_APFS


  2. FredT2 macrumors 6502a

    Mar 18, 2009
    It is physically two separate sticks controlled by T2 chip, no RAID.
  3. zarf2007 thread starter macrumors regular

    Aug 27, 2010
    London, UK
    ah ok thanks
  4. RyanXM macrumors 6502


    Jul 7, 2012
    DFW, TX
    I would imagine the T2 Chip is making the separate physical drives into a LVG (Logical Volume Group). I haven't seen any evidence of it RAIDing them.
  5. wardie macrumors regular

    Aug 18, 2008
    Does an LVG give you striping even if it’s not RAID0? I’m sure I saw some performance figures which indicated high speeds that you thought would only come from that type of config >2GB/s.
  6. RyanXM macrumors 6502


    Jul 7, 2012
    DFW, TX
    I'd have to dig into how the LVG handles the data transfers, but given that a "Fusion HD" is just an LVG group, software knows which volume is "faster", so I'd imagine you would see some benefits. Aren't write speeds higher than reads on the iMac Pro?
  7. curmudgeonette macrumors 6502

    Jan 28, 2016
    There's no significant controller on the individual SSD halves. Therefore, I suspect they are simply two banks of SSD chips. Just like two RAM DIMMs forming a 128 bit wide memory system.
  8. bplein macrumors 6502a


    Jul 21, 2007
    Austin, TX USA
    So, if I told you it was one stick, or two, or 4... other than curiosity, what does it matter?

    My solid bet is that the T2 is striping across 2 sticks. This gives better performance and write leveling BUT higher risk of failure. But you should be backing up regularly and even doubling the failure rate by striping across 2 devices is probably more reliable (lower failure rate) than a single HDD of old...

    ---- added later ----

    By the way, a single SSD will stripe across many chips internally. More chips means more chances of failure, but higher performance. But you don't hear people complaining that several chips are used inside an SSD.

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7 March 1, 2018