[CentOS] Poor RAID performance new Xeon server?

William Warren hescominsoon at emmanuelcomputerconsulting.com
Sun Jan 11 00:55:09 UTC 2009


Stewart Williams wrote:
> I have just purchased an HP ProLiant HP ML110 G5 server and install ed 
> CentOS 5.2 x86_64 on it.
>
> It has the following spec:
>
> Intel(R) Xeon(R) CPU 3065  @ 2.33GHz
> 4GB ECC memory
> 4 x 250GB SATA hard disks running at 1.5GB/s
>
> Onboard RAID controller is enabled but at the moment I have used mdadm 
> to configure the array.
>
> RAID bus controller: Intel Corporation 82801 SATA RAID Controller
>
> For a simple striped array I ran:
>
> # mdadm --create /dev/md0 --level=0 --raid-devices=2 /dev/sdb1 /dev/sdc1
> # mke2fs -j /dev/md0
> # mount -t ext3 /dev/md0 /mnt
>
> Attached are the results of 2 bonnie++ tests I made to test the 
> performance:
>
> # bonnie++ -s 256m -d /mnt -u 0 -r 0
>
> and
>
> # bonnie++ -s 1g -d /mnt -u 0 -r 0
>
> I also tried 3 of the drives in a RAID 5 setup with gave similar results.
>
> Is it me or are the results poor?
>
> Is this the best I can expect from the hardware or is something wrong?
>
> I would appreciate any advice or possible tweaks I can make to the 
> system to make the performance better.
>
> The block I/O is the thing that concerns me as mostly I am serving a 
> 650MB file via samba to 5 clients and I think this is where I need the 
> speed.
>
> Plus I am hoping to run some virtualised guests on it eventually, but 
> nothing too heavy.
>
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>
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That onbard raid is fakeraid..so when you dialup raid 5 you effectivly 
put hte hdd's in pio mode since ALL data has to be routed through your 
cpu.  Please get a raid card from HP or go get a 3ware card so you ahve 
real hardware raid.

fake and real raid chpsets:
http://linuxmafia.com/faq/Hardware/sata.html

Why using fakeraid at all is bad:
http://thebs413.blogspot.com/2005/09/fake-raid-fraid-sucks-even-more-at.html

MDM under linux is kernel raid that does not use a binary 
driver..however you don't want to do ANY software raid 5. 


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