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A little concerned with throughput on RAID-5

A

awsiemieniec

Gawd
Joined
Jul 2, 2004
Messages
810
I have 5 X Ultra320, 15K RPM drives setup on an Adaptec 2230SLP with 256MB cache...yeah, it's an expensive setup to say the least. I was checking out the speed of the array and comparing it to my much cheaper I/O setup on my HTPC (2 X SATA 150 drives in RAID-0, yeah I know it's not technically RAID by definition, attached to the on-board SATA RAID ports). On my HTPC, I was averaging 87 MB/sec. On my system in question with the SCSI RAID-5, I was only getting about 53 MB/sec. (I need to go home and run the tests again just to make sure I'm reporting the correct numbers - but regardless, the RAID-5 system that I shelled out close to $1900 for was much slower in the test) This has me losing sleep at nights. :) I use the system for primarily gaming and sometimes I take work home and do VB programming, so I guess I could re-do the RAID-5 into a RAID-0 (forget about the "failsafe"). But before I do all that, does anyone have any opinion as to why it's so slow. We're talking about Ultra320drives on a controller PCI-X 2230SLP SCSI-RAID. That beast should be flying fast!

I don't have any slower devices on the same channel as these HDDs. On channel B I have an 80MB/sec HDD, but that shouldn't slow it down on channel A (right????). And the RAID card is installed into a PCI-X slot on the mobo (SuperMicro P4SCT+II) Any ideas?
 
Review here: http://www.tweakers.net/reviews/557/29

The 2230SLP is not the strongest at RAID 5.

If you get a good hardware RAID 5 card, you would be doing somewhat better. But remember RAID 5 is not performance oriented. It is reliability first, with performance still considered, but second.

Also what benchmark are you using (many are not very good)

And last but not least, are all your drivers up to date? (chipset, RAID, etc.)

==>Lazn
 
Yeppers, RAID-5 is a capacity and fault tolerance tool, not a performance tool. Questions:

A) What mobo are you using, and which expansion slot on that board are you using?
B) Cables etc. - you might be running at something bizarre like Ultra 3 because of a 'weakest link' in a BIOS setting, SCA adapter, cable, etc.
C) RAID-5 isn't a great choice for tasks with frequent writes, such as typical desktop use.

RAID 0+1 with the fifth drive as a hot spare, would be a good choice, and I'd bet you'd pull over 100MB/sec in such a configuration. Another option would be to take the fifth drive, used it as a SLED boot drive, and go with 0+1 for the other 4 drives. Also, the 15K.4 isn't the zippiest current generation 15K drive out there, although it does continue to stick to Seagate's strengths of quiet operation and reliability, so I don't fault you for picking them up.
 
DL, he listed the board in his first post; it's also in his sig. :p

Make sure that PCI-X slot is set to at least 66MHz or Auto if you can help it. BIOS should give you the bandwidth available for that bus. Should be 528MB/s with a 64-bit/66MHz bus.

But generally no, RAID 5 isn't about performance in the slightest.
 
This image is from HD Tach. Test was just run during my lunch hour. Top image is the system in question, bottom is from the HTPC. Test was with the 32MB zone. Previous numbers quoted were from a program called "HD Tune".

Main.JPG

HTPC.JPG
 
DougLite said:
A) What mobo are you using, and which expansion slot on that board are you using?
B) Cables etc. - you might be running at something bizarre like Ultra 3 because of a 'weakest link' in a BIOS setting, SCA adapter, cable, etc.
C) RAID-5 isn't a great choice for tasks with frequent writes, such as typical desktop use.
QUOTE]

A.) SuperMicro P4SCT+II Slot: 3
AGP card is a "double wide" causing top PCI-X to be covered. Sticking the RAID controller in PCI-slot #2 is too close causing the NVSilencer fan (center of fan) to rub on the corner of the RAID card. So I was forced to put in PCI #3

B.) Cables are from Adaptec and are guarenteed U320 cables

C.) Thinking of trying out RAID-0. Am on current firmware and drivers.
Click to expand...
 
awsiemieniec said:
A.) SuperMicro P4SCT+II Slot: 3
AGP card is a "double wide" causing top PCI-X to be covered. Sticking the RAID controller in PCI-slot #2 is too close causing the NVSilencer fan (center of fan) to rub on the corner of the RAID card. So I was forced to put in PCI #3

B.) Cables are from Adaptec and are guarenteed U320 cables

C.) Thinking of trying out RAID-0. Am on current firmware and drivers.
Click to expand...

Well according to this review all the PCI-X slots are 66mhz (and of course 64 bit) so being in slot 3 should not be a problem.. (you could try it temporarily in Slot 2 just to see if it makes a difference, if it doesn't stay there it should not cause a heat problem)

==>Lazn
 
Try running atto (google: atto benchmark)
I had a raid 5 running on old mylex adapter, like scsi2 LVD 80mbytes/sec.
hdtach would report 20mbytes/sec but atto would report near 80 when running overlapping I/O.
 
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