Very Slow RAID-5 Reads

Hello, I got a RAID-5 array consisting of 8 drives 1 of them is standby. This array was rebuilt today after a failure. I get somewhat good speeds in write but VERY slow speed on read. It starts out fine and a couple of seconds it goes to 0 bytes and so on... Here is my Crystal report:

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CrystalDiskMark 5.0.2 x64 (C) 2007-2015 hiyohiyo
                           Crystal Dew World : http://crystalmark.info/
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* MB/s = 1,000,000 bytes/s [SATA/600 = 600,000,000 bytes/s]
* KB = 1000 bytes, KiB = 1024 bytes

   Sequential Read (Q= 32,T= 1) :   321.858 MB/s
  Sequential Write (Q= 32,T= 1) :   283.666 MB/s
  Random Read 4KiB (Q= 32,T= 1) :     3.815 MB/s [   931.4 IOPS]
 Random Write 4KiB (Q= 32,T= 1) :     0.487 MB/s [   118.9 IOPS]
         Sequential Read (T= 1) :   127.089 MB/s
        Sequential Write (T= 1) :   283.765 MB/s
   Random Read 4KiB (Q= 1,T= 1) :     0.757 MB/s [   184.8 IOPS]
  Random Write 4KiB (Q= 1,T= 1) :     0.370 MB/s [    90.3 IOPS]

  Test : 1024 MiB [I: 96.1% (10741.8/11177.5 GiB)] (x5)  [Interval=5 sec]
  Date : 2015/08/23 20:59:31
    OS : Windows 10 Professional [10.0 Build 10240] (x64)
LVL 3
infernumAsked:
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Davis McCarnOwnerCommented:
Unfortunately; with RAID, its almost impossible to check the individual drives; but, I suspect one of the other drives is on the verge of failing.  If you have another PC available, you can connect each drive, one at a time to inspect and/or test it with the free trial of http://www.hdtune.com .  Hook the drives up where the DVD drive was, run HDTune, and change it to one of your drives.  On the health tab, if the data value of reallocated sectors (05) or pending (C5) is NOT 0 (zero), the drive is beginning to fail.  If you really want to be sure, run the error scan.  One red box is doom.
Be very careful to mark the drives so they go back in the right place!
pgm554Commented:
What type of RAID controller?
What model disks?

If it's one of those onboard fake controllers without cache,I would dump it and use the windows 10 Storage Spaces with refs.

http://windows.microsoft.com/en-us/windows-8/storage-spaces-pools
infernumAuthor Commented:
Its a Highpoint Rad 2722 SAS controller and disks are Hitachi Deskstar 3.5-Inch 2TB 7200RPM SATA III 6 Gbps 64 MB Cache Internal Hard Drive (0F12115)

I fixed it by upgrading to th latest driver for the SAS card on windows level now I am getting high speeds read and write.

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pgm554Commented:
Very bad idea to use consumer grade disks and hardware RAID 5.

The difference is the way consumer grade disks act when they encounter a bad spot on the drive.

They can take 15 to 30 seconds trying to read or write before they give up and mark sector as bad.

If you are using hardware RAID,the controller after 7 seconds will flag that disk as bad(even though the disk might be good)
Then you would need to do a rebuild and if you are doing a rebuild (which on those size disks take many hours)and another disk times out ,your array is toast.

Use the Ultrastars ,there's a reason why thay are rated for hardware RAID.
infernumAuthor Commented:
I found the answer myself
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