LSI 9361 RAID5 slower with cachecade - is that normal ???

Discussion in 'RAID Controllers and Host Bus Adapters' started by minimini, Oct 27, 2017.

  1. minimini

    minimini Member

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    I have one ST200FM0073 (Seagate SAS SSD, 185 GB, 12GB/s) as cachecade drive. When I use it to cache RAID 5 i get worse results than without using that SSD as the cache.

    In other words:

    - SSD as independent virtual drive (not CC drive) has performances 1 GB/s read/write. (SSD 12GB/s)
    - SSD as CC on RAID 5 reduces speed of raid to 400MB/s (6x 4TB Seagate SAS 6GB/s drives)
    - RAID 5 without CC goes to 900 MB/s (6x 4TB Seagate SAS 6GB/s drives)

    What is happening here ???
     
    #1
    Last edited: Oct 27, 2017
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  2. KioskAdmin

    KioskAdmin Active Member

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    Cache fill speeds aren't that fast for a small benchmark. Real world will be good
     
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  3. minimini

    minimini Member

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    Raid drive is empty. It has one 10GB single file. It goes twice faster without CC than with CC. This is real life test for me.... Are you sure there isn't some other problem here ??
     
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  4. i386

    i386 Well-Known Member

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    Are you sure that you're not getting this nummers from the controller ram?

    I see a read/mixed load optimized ssd in the specs:
    Screenshot-2017-10-28 1200-ssd-ds1781-4-1310gb pdf.png
     
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  5. minimini

    minimini Member

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    I will try putting CC drives in raid and see if it improves performance. Thx for the table.
     
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  6. aron

    aron New Member

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    i have been experimenting with cachecade,

    My conclsuion is that its not particularly good for sequential reads, which is what i care most about as i typically use the raid array on the server for backing up video editing projects, and copy the files to work station for working. And also use the array for raw photo data (80mb/photo) for adobe lightroom on PC.

    I have 11 spinning drives and 5 SSDs.

    The spinning drives do around 1,5 tb/sec squential read in raid 5. The SSDs around the same.

    Add the SSDs as a cashecade, and a warm cache, and i get sequential reads of 800 mb/sec. The general finding supported by other who have tested.

    So dissapointed on cachecade for my use i.e. sequential read, but probably good for database etc.
     
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  7. minimini

    minimini Member

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    Thanks Aron, I come to the same conclusion. Here is one more crazy finding.
    - I created raid 5 on LSI 9361 + memory + bbu+ cachecade
    - I imported that very "foreign" raid 5 to IBM 5210 +memory + bbu + cachecade
    (basically I just switched controllers; plugged in cables, and that's it) and :::::

    Performance on IBM 5210 is 50% slower. Just to say, it's same controller, same chipset.... EEEK !!!
     
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  8. minimini

    minimini Member

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    This is good remark, I thought if I use 10GB file I will eliminate advantages of 1 GB ram cache on the controller.
     
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  9. minimini

    minimini Member

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    Anyway, to close this thread with some decent evidence/tests; I attach two images of raid-5 benchmark with and without cachecade.

    RAID 5 - No CC
    RAID5_NO_CC.png
    RAID 5 - with CC
    RAID5_CC.png
    6 x Seagate Constellation 4T SAS 6G on RAID 5
    2 x Seagate ST200FM0073 200GB SAS 12G on RAID 0 as CC
     
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  10. i386

    i386 Well-Known Member

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    Throughput:
    Read / Write @ 4k > worse
    Read / Write @ 512k/sequential > better

    Latency:
    Read > 10 times better
    Write > 6 times better
    :eek:
     
    #10
  11. mrkrad

    mrkrad Well-Known Member

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    change the strip size!
     
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