On Jan 11, 2009, at 10:13 AM, Stewart Williams <lists at pinkyboots.co.uk> wrote: > 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. >>> >>> --- >>> --- >>> ------------------------------------------------------------------ >>> >>> _______________________________________________ >>> CentOS mailing list >>> CentOS at centos.org >>> http://lists.centos.org/mailman/listinfo/centos >> 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. If all your doing is serving a single file to a handful of PCs then a 2 drive mirror will be more then enough. You should stick with the OS RAID though as the onboard RAID will bring nothing but pain. For sequential IO expect 60MB/s read and 40MB/s write (with the drive's write cache enabled) per drive. Random IO is an order of magnitude less. -Ross