Poor RAID5 performance

[joblo37pam]

I recently inherited a Dell PowerEdge SC1420 that I plan to use as a test rig for SBS 2008. It has a CERC SATA 1.5 6ch controller in it (rebadged Adaptec).

The controller supports RAID 5 and I had three 500GB Seagate ES.2 drives laying around, so I assumed that would be the way to go. Unfortunately, I can't get it to perform worth a damn. HDTune shows an average 45mb/s read speed even after full build/verify of the array (which took ~30 hours), while each drive individually connected to the onboard SATA gets ~105mb/s. Raid1 and JBOD don't perform any better.

I haven't updated BIOS/firmware yet, and that will be my next step if there are newer available, but I was wondering if anyone had any experience with this controller and whether these numbers are normal? I was really hoping for better, but may have to upgrade to a better controller. I just don't want to drop much money into this box.

Thanks for the help.

 

[sub.mesa]

Could be your controller yeah. Do you have any benches we can look at?

 

[joblo37pam]

I haven't taken any screenshots, but I can. I'll play with it a little more today and see what I can come up with.

 

[Blue Fox]

That RAID card is ancient and slow. You'll have to replace it if you desire better performance.

 

[joblo37pam]

That RAID card is ancient and slow. You'll have to replace it if you desire better performance.

I know it's old, but I at least expected it to get equal or better performance to the onboard controller, especially with RAID5 or 0. Instead, the onboard is over twice as fast.

I ran some more tests this morning just for comparison:

This is the onboard controller with a single disk.

This is the CERC controller with all three disks configured as JBOD

This is the CERC controller with all three disks in RAID0 (64k Stripe)

This is the CERC controller with all three disks in RAID5 (64k Stripe) - the array was still in build/verify mode for this one.

 

[sub.mesa]

If you want to do simple STR benchmarks; test in the filesystem instead. Buy or download HDTune Pro and run the File benchmark instead; at least in some benchmarks it would give higher numbers; and those are actually real as its running off the filesystem.

The normal HDTune benches are done at raw disk I/O with queue depth of 1, not suitable for any RAID array.

 

[joblo37pam]

Thanks for the tip on the RAW vs NTFS. Here is a sample of the results with HDTunePro. They are pretty similar regardless of the file size chosen.

 

[joblo37pam]

Since this controller is pretty obviously useless for what I want to do, what would you all suggest for a controller that I can pick up on the cheap? I've already dropped more money on this thing than I wanted, but I need to finish it up.

PCI-e (x1 or x8) would be nice for future-proofing, but PCI-X would also work if the price is right. SAS would also be nice, but not necessary. I'd like to keep it around $100 if possible, but could be persuaded to spend more on the right card.

LSI 300-8X?
3Warre 9500s?
Perc 5i?
Something else?

 

[sub.mesa]

Re-run HDTune Pro benchmark, click the File Benchmark tab and set file length to a large value and delay to something like 2. Then run the benchmark.

The raw read benchmark may not work properly on RAID-arrays since it uses an artificial queue depth of 1.

 

[nitrobass24]

That dell card just sucks, theres not much you can do about it.

Get something else or use the onboard controller.

 

[drescherjm]

This looks worse than software raid on windows (which sucks because it tends to cause every write to read first). Although this is a read test. I have no explanation for this abysmal performance. I would expect 125 to 150MB/s on a linux software raid and the same 3 disks and same cpu.

BTW, raid5 with only 3 disks is far from optimal. At work I generally do not do raid5 unless I have at least 5 drives in the array.

 

[joblo37pam]

Re-run HDTune Pro benchmark, click the File Benchmark tab and set file length to a large value and delay to something like 2. Then run the benchmark.

The raw read benchmark may not work properly on RAID-arrays since it uses an artificial queue depth of 1.

The last picture I posted was with the file benchmark. That particular one was only with a 32kb file length, but things were almost identical with all the sizes. I will try it again with a delay of 2 and see if that makes a difference, but I have pretty much given up on this controller.

Any comments on what I should replace it with?

I realize that a 3 disk array isn't necessarily optimal, but this is a machine put together out of spare parts for testing purposes. It doesn't need to be great. I had the three matching disks, so I'll use them.

The onboard controller only has two ports, so that is pretty limiting.

 

[sub.mesa]

Your controller does not do write-combining, that means every write will be 2-phase; very slow. It will also wear your drive by excessive seeking if you do this alot.

You should get another controller, or use software RAID instead. You might also settle for RAID0 and use a good backup instead.

 

[nitrobass24]

Could grab a Perc5/i or a Perc6/i.
From what i can tell you have an x8 expansion slot so that really opens the doors.

Whats your budget?

 

[joblo37pam]

Could grab a Perc5/i or a Perc6/i.
From what i can tell you have an x8 expansion slot so that really opens the doors.

Whats your budget?

From above:

Since this controller is pretty obviously useless for what I want to do, what would you all suggest for a controller that I can pick up on the cheap? I've already dropped more money on this thing than I wanted, but I need to finish it up.

PCI-e (x1 or x8) would be nice for future-proofing, but PCI-X would also work if the price is right. SAS would also be nice, but not necessary. I'd like to keep it around $100 if possible, but could be persuaded to spend more on the right card.

LSI 300-8X?
3Warre 9500s?
Perc 5i?
Something else?

 

[nitrobass24]

If you are willing to break your budget a little bit you can get a Perc6/i w/ BBU for 165

Didnt really see a better deal for a Perc5i right now, but they are usually cheaper.
Either one will provide much better performance than what you have now.

 

[joblo37pam]

If you are willing to break your budget a little bit you can get a Perc6/i w/ BBU for 165

Didnt really see a better deal for a Perc5i right now, but they are usually cheaper.
Either one will provide much better performance than what you have now.

That's really not a bad price if it is really BNIB. The SAS and PCI-e would be nice, but I'm not sure if it comes with cables. It says it has the BBU cable, but doesn't mention the fanout cable. I emailed him to see.

Any other suggestions?

Edit: He wants $25 per fanout cable. I think I'll pass. There are a few other 6i's coming up that I may keep an eye on, unless someone has a better suggestion.