AVS › AVS Forum › Video Components › Home Theater Computers › RAID5 typical problem? (very low write speed: 6MB/s)
New Posts  All Forums:Forum Nav:

RAID5 typical problem? (very low write speed: 6MB/s)

post #1 of 11
10/13/08 at 10:58am
Thread Starter 
I'm sorry if there is another topic telling how to solve this issue, I've read about 12 topics here and hundreds out of here, microsoft papers, manuals, etc.
I've a TX4650 by promise. My problem is as follows:
If I try to copy a file from anywhere (a pata disk, a sata disk, another raid (of another controller) disk, lan disk) to the RAID5 it begins copying at about 40-50MB/s but after a few seconds the speed drops to ~ 6MB/s and remains there. Some kind of system activities (open a file, run a program or move a window) randomly increase that speed for a few seconds to 40-50MB/s and then drops to 6MB/s again.
When running at "expected" speed the CPU usage is about 30-40%. If not drops to 5-6%.

If I put "6MB/s RAID5" in google there are lots of results but no solution. I hoped here maybe someone had the same problem as me and solved it.

The system can write at 40-50MB/s that is for sure, the problem is why it stops doing it suddenly after a few seconds, and why some random events make it wake and run fast for some other seconds.

I've tried:
- Contacted to Promise. They reply fast with no solutions.
- Put the controller on an independent irq. No resuts.
- Redo the raid. No results.
- Increase "numberofrequests" registry parameter. No results.
- Disable secondari IDE. No results.
- Disable the other controler (TX4310). No results.
- Use an older driver. No results.
- Disable/enable write cache of the disk (administration panel). No results.
- Enable/disable write cache on every disc (via webpam). No results
- Check if the raid LBA allocation is correct (128MB displacement). No results.
- Enable/disable antivirus (ESET Smart Security Businnes). No result.

The system:
Windows Server EE 2003 SP2
ASUS M2NPV-VM bios 1401 (latest)
pci-e Promise TX4650 with 4x seagate 1TB ES.2 (ST3100340NS) RAID5
1 logical drive GPT 2.7TB
Windows is on a PATA disk.
Using latest bios/drivers available for TX4650.
Reply
Reply

AVS Top Picks

post #2 of 11
10/13/08 at 11:15am
bad controller?
Reply
Reply
post #3 of 11
10/13/08 at 11:41am
Buy a real RAID controller.
Reply
Reply
post #4 of 11
10/13/08 at 12:22pm
Quote:
Originally Posted by Valnar View Post

Buy a real RAID controller.

What do you recommend for under $300? PCI-e.
Reply
Reply
post #5 of 11
10/13/08 at 12:52pm
Look at Areca or 3Ware. I myself have a Highpoint 2320 which is cheaper, but runs great for my needs. If you need more write throughput, Areca or 3Ware is the way to go.
Reply
Reply
post #6 of 11
10/13/08 at 12:59pm
I checked the specs for this card and couldn't figure out where they do write-buffering - in the host or in the controller. My guess is that when the test first starts running it's writing to the buffer and able to do full stripe writes. Then the buffer fills up and enters a read/modify/write mode (pure supposition) which will have HORRIBLE write performance. If the buffering was in the host then you could increase the size and postpone the drop in performance. Also, using a smaller stripe size could cause the controller to stay in full stripe write mode longer, or avoid whatever bug is causing them to use the buffers poorly.

I hate to say it, but regardless of the buffer size the algorithm should still use the buffer effectively to stay in full stripe write mode, even at a lower transfer rate, but as Valnar said it is just a Promise card. I suspect that this is simply a poor buffer management algorithm. Most RAID cards under $300 are going to have issues like this. To get real RAID joy you're going to need a card that has been shipped by OEMs, and be prepared to spend $500-$1000. I'd recommend companies like LSI, 3Ware, Adaptec and Intel. Even though they don't have OEM experience, Areca and RAIDCore seem to also be doing well.
Reply
Reply
post #7 of 11
10/14/08 at 4:59am
Thread Starter 
I would do with 20-30MB/s write speed. That is why I did not buy an expensive card. Also I don't need 100 or 200 MB/s read speed just some redundancy vs. price. But I wasn't expecting 6MB/s.
Even if the cpu does the xor stuff 6MB/s is too poor.

@HAppyFunBoater: I thought about some buffer problem too. But this time promise support is being late to answer me. I've also read about bad alignment can cause very poor write performance, but to check that is beyond my knowledge.

Finally I've tested them with crystaldiskmark 2.2 with 5 x 1000MB and it rates at 20MB/s write speed. That is more than 3 times faster and enough for me.

I just was wondering if someone else have had the same problem and have been able to solve it.
Reply
Reply
post #8 of 11
10/14/08 at 6:48am
Quote:
Originally Posted by calamarcillo View Post

I would do with 20-30MB/s write speed. That is why I did not buy an expensive card. Also I don't need 100 or 200 MB/s read speed just some redundancy vs. price. But I wasn't expecting 6MB/s.
Even if the cpu does the xor stuff 6MB/s is too poor.

@HAppyFunBoater: I thought about some buffer problem too. But this time promise support is being late to answer me. I've also read about bad alignment can cause very poor write performance, but to check that is beyond my knowledge.

Finally I've tested them with crystaldiskmark 2.2 with 5 x 1000MB and it rates at 20MB/s write speed. That is more than 3 times faster and enough for me.

I just was wondering if someone else have had the same problem and have been able to solve it.

Yeah, the CPU can definitely XOR faster than 6MB/s. That's not the problem. If you had a SATA analyzer you could check to see if read/modify/write is occuring, but there's not much you can do about it.

Did you try a smaller RAID-5 stripe size?
Reply
Reply
post #9 of 11
10/15/08 at 8:20am
Quote:
Originally Posted by calamarcillo View Post

I would do with 20-30MB/s write speed. That is why I did not buy an expensive card. Also I don't need 100 or 200 MB/s read speed just some redundancy vs. price. But I wasn't expecting 6MB/s.
Even if the cpu does the xor stuff 6MB/s is too poor.

...

Finally I've tested them with crystaldiskmark 2.2 with 5 x 1000MB and it rates at 20MB/s write speed. That is more than 3 times faster and enough for me.

I just was wondering if someone else have had the same problem and have been able to solve it.

I have an AMD SB750 based RAID-5 array. Three Seagate 640GB drives. Some of the technology (at least the managment GUI) comes from Promise AND I get ~30-40 MB/s sustained write speeds doing real world copy operations. The SB-750 MB cost me an extra ~$10 compared to the SB-700 based MB I bought ~six months ago. Well worth the ~$10...
Reply
Reply
post #10 of 11
10/15/08 at 2:47pm
Thread Starter 
Quote:
Originally Posted by HappyFunBoater View Post

Yeah, the CPU can definitely XOR faster than 6MB/s. That's not the problem. If you had a SATA analyzer you could check to see if read/modify/write is occuring, but there's not much you can do about it.

Did you try a smaller RAID-5 stripe size?

It can't be changed. 16k. I also tried with a smaller disk (<2TB) dynamic, basic-gpt. It doesn't matter, it doesn't work.

I uploaded a video of what happens:
http://www.megaupload.com/es/?d=FDFAQBYI

I send it to promise but I have had no answer for 2 days...
Reply
Reply
post #11 of 11
10/15/08 at 3:08pm
Quote:
Originally Posted by calamarcillo View Post

It can't be changed. 16k. I also tried with a smaller disk (<2TB) dynamic, basic-gpt. It doesn't matter, it doesn't work.

I uploaded a video of what happens:
http://www.megaupload.com/es/?d=FDFAQBYI

I send it to promise but I have had no answer for 2 days...

16KB is already pretty small. It seems that roughly 72MB is transferred before performance drops off, which isn't an unreasonable size for a buffer (assuming this is a buffer overflow problem).

Sorry, bud. I've got no idea. It definitely sounds like a Promise bug.
Reply
Reply
New Posts  All Forums:Forum Nav:
  Return Home
  Back to Forum: Home Theater Computers

AVS Top Picks

AVS › AVS Forum › Video Components › Home Theater Computers › RAID5 typical problem? (very low write speed: 6MB/s)