Dell Perc 6/E and MD1000 Poor RAID50 Performance

[maxxoverclocker]

Hi guys, I have a Poweredge R710 at work with a PERC 6/E SAS card, along with a brand new Powervault MD1000 with 15 2TB SAS 7200rpm drives.

The performance is as follows:

http://img23.imageshack.us/img23/4819/percr.png


This disk copies over to some tape drives than NEED 120mb/s if it drops lower than that even for a second- the tapes encounter SEVERE performance issues.

I called dell and they said essentially that this is to be expected. :mad: I'm running a RAID50 (3 RAID 5's in a RAID0.) He gave me some crap about how advanced the algorithm was to calculate the hashes for a RAID50. I kind of told him that essentially what he was saying is I spend $14,000 on an array of hard disks that my 14dollar flash drive could out perform?


His only suggestion was to change from a RAID50 to a RAID5. Does anyone have any suggestions on where to go for this? I have the latest firmwares and drivers... Or was he telling the truth about this?

Any help would be appreciated.

Thanks!

[maxxoverclocker]

Anyone have any suggestions?

[||Console||]

That looks like really bad , but I have no exp with raid 50 what Os are you running ?
Can you run ATTO and Crystal diskmark ?

[ratbuddy]

If it was going 250-275MB/s straight across I'd say it was fine, but something is funking things up - why the heck is it dipping down below 23 MB/s?

[Xaotic]

Or was he telling the truth about this?


Quite possibly he was. The Perc 6/E is a decent controller, but that is a very complex set of parity calculations. Writes are going to be intermittently slow due to the calculations of three disparate parity sets.

I do not currently have a set of drives on a MD1000 that I can split, but do have a 14 drive RAID-6 set of 15K 300GB SAS. This yields a bit lower write performance than RAID-5, but gives an overall level of expectations. Using HD Tune, it still has a drop to 14.9MB/s.

If you need better, more consistent performance I would recommend RAID-10. I cannot currently verify performance criteria as the systems using it are under load by DB servers.

The SATA drives are likely partially culpable in the issue, as they support lower IOPs than the SAS drives. Other usage of the array could also be a cause. Is the array free of other activity while the tape jobs are running?

EDIT: Have you aligned the partitions on the array? This can lead to substantial drops in performance is the array is not aligned properly. Use the diskpart.exe section to correct after making sure that you have the correct offset.

http://msdn.microsoft.com/en-us/library/dd758814.aspx

[maxxoverclocker]

Thanks for your help you guys. I've determined that if ABSOLUTELY nothing is accessing the disk- the benches are fine. But if theres anything at all... (a 2gb file download over a 22megabit connection) the performance is absolute crap. I'm assuming it's the RAID mode i'm in so I guess I'll have to wipe the drive clean and start from scratch...

Quite possibly he was. The Perc 6/E is a decent controller, but that is a very complex set of parity calculations. Writes are going to be intermittently slow due to the calculations of three disparate parity sets.

I do not currently have a set of drives on a MD1000 that I can split, but do have a 14 drive RAID-6 set of 15K 300GB SAS. This yields a bit lower write performance than RAID-5, but gives an overall level of expectations. Using HD Tune, it still has a drop to 14.9MB/s.

If you need better, more consistent performance I would recommend RAID-10. I cannot currently verify performance criteria as the systems using it are under load by DB servers.

The SATA drives are likely partially culpable in the issue, as they support lower IOPs than the SAS drives. Other usage of the array could also be a cause. Is the array free of other activity while the tape jobs are running?

EDIT: Have you aligned the partitions on the array? This can lead to substantial drops in performance is the array is not aligned properly. Use the diskpart.exe section to correct after making sure that you have the correct offset.

http://msdn.microsoft.com/en-us/library/dd758814.aspx

[login]

Hi maxxoverclocker,

Did you manage to resolve your issue? I'm looking at a Dell MD1000 with 8*7200RPM NL SAS drives in RAID10 with the Perc6/E for a san-on-a-budget to replace our slow NAS devices...

This thread is the only thread i've seen anywhere that has benchmarks of the MD1000 using 7200RPM drives... does anyone have any benchmarks of this MD1000 unit using a more Common raid - i.e. RAID5 or RAID10 .... is the issue of the benchmarks dipping to very low speeds like in your post above still there??

Thanks in advance :)

[login]

*bump* ... Anyone here with a Dell MD1000 :-/ ?