I have an Intel RS2WC080 RAID controller card connected to an array of 8 WD Black 4TB SATA3 drives, in a RAID5 configuration.

While the read speed is ~750MB/s the write speed hovers around 45MB/s. I know RAID5 is slower for writes, but this is not exactly what I expected with this setup. On an older machine, a Mac with a similar sized RAID 5 array using the same kind of physical drives I get around 430MB/s write and 450MB/s read.

I tried some of the suggestions from the Intel site; http://www.intel.com/support/motherboards/server/sb/CS-029227.htm but a lot of the options - like setting write cache policy to 'Write Ahead' and read ahead policy to 'Adaptive Read Ahead' - aren't possible either in the RAID BIOS settings or the Web Console software.

Another thing that's annoying is that it disconnects every time the computer sleeps, and doesn't reconnect on wake. The symptoms are that the volume doesn't show up at all to the OS - if I open the Windows Disk Management program it's visible at all. I'm coming back to windows after a while away, so I'm not sure where I'd find logs to look at.

Can anyone give me pointers on how to improve this situation?

Additional info: Z9PE-D8 mobo, 2 x (Intel E5-2690 x 10 cores @ 3.0Ghz), 64Gb RAM, Windows 7 64-bit

EDIT: it looks like Intel are playing sillybuggers somehow. Although they list it as a RAID 5 compatible card, it's based on an LSI AS2008 chip which only does 0, 1, 1E and 10. This could have something to do with it.

  • Some people out there claim those drivers get 80-150MB/s. So higher read speeds are due to caching AND/OR raid. Higher write speeds are due to caching. – LatinSuD Aug 21 '14 at 15:00
  • Start testing with a qualified test tool to measure your raid speed, like hddscan (free) or Passmark's PerformanceTest or hdtune. Or even better: burn a copy of Hiren's boot CD and use any of the available tests there to measure you disk's performance (and by that excluding any Microsoft voodoo). Please report any qualified results back and we'll be able to help you better. – agtoever Aug 24 '14 at 12:06
  • "Another thing that's annoying is that it disconnects every time the computer sleeps, and doesn't reconnect on wake." Your RAID disconnects on sleep? Can you expand on that? In what way does it "disconnect"? – Ƭᴇcʜιᴇ007 Aug 25 '14 at 20:11
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    Also, are you running the latest firmware? You should be seeing version 2.130.394. The list of fixes between the last two releases is quite lengthy. – Jason Aug 25 '14 at 21:39
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    Can I ask if the Mac was using the same RAID card? Because if it wasn't, that's definitely relevant. The RS2WC080 datasheet on the intel website (ark.intel.com/products/43164/Intel-RAID-Controller-RS2WC080 -> click 'datasheet') says that it uses an LSI SAS2008 controller and the LSI website for that controller (lsi.com/products/io-controllers/pages/lsi-sas-2008.aspx#tab/…) says it doesn't support RAID 5. It's possible that software/firmware on the card or the driver in the OS is implementing it instead which is why it's slow. Or not. This is just an educated guess :) – Jon Kloske Aug 26 '14 at 0:25

@JonKloske: I think you nailed it. That card doesn't seem to be a real RAID5 card, despite what Intel says. Last time I buy an Intel RAID card.

I returned it and got an adaptec card installed instead, and it's writing at ~450MB/s and reading at around 700MBs, so I'm a happy camper. I haven't tested to see how it copes with putting the system to sleep yet. Thanks for all the help people.

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