[CentOS] Poor RAID performance new Xeon server?

Stewart Williams lists at pinkyboots.co.uk
Sun Jan 11 15:13:13 UTC 2009


William Warren wrote:
> 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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> 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. 

Thanks William,

I am no expert on RAID, so you have opened my eyes to somethings I 
wasn't aware of.

I am considering disabling the onboard RAID in the BIOS and 
re-installing CentOS and configuring the 4 drives as RAID 10 just to see 
what the performance is like.

Or I may purchase a card as you advise. Would I benefit from buying a 
SCSI/or SAS card and drives for my requirements? Basically the main role 
of the machine is to serve a ~600MB file via samba to 5 Windows XP cient 
PC's on a gigabit network.

Stewart


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