Terrible RAID 5 performance after upgrade

[darkfalz]

I went from 4x2TB (Seagate Barracuda LP, a few years old) which wrote at over 100 MB/sec with write cache enabled to a 5x4TB with new Desktop 15 HDDs, but even after initializing and re-enabling the cache, the write speed maxes out at a disgusting 26.7 MB/second. Read speed is over 500 MB/sec.

This is plainly unacceptable but I can't for the life of me figure out what happened. I updated to latest software, and no change.

Any ideas?

 

[Concillian]

were both in RAID-5 before and after? Same controller for both arrays?

RAID 5 on a low end controller offers really poor write speed due to the parity calculated in software. I even had an old 3ware card that would hit a pretty low ceiling on writes in RAID 5 due to parity calculations.

 

[darkfalz]

Before was 4x2TB as I said, same chipset, same settings, but well over 100 MB/sec write.

New one is 5x4TB and write 26 MB/sec no matter what write cache settings are.

 

[sub.mesa]

Show us the data! With data we can give you better advice.

You're probably using Intel RST RAID; so next time include this very important information in your thread. I'd also like to see SMART attributes of your drives, gathered with CrystalDiskInfo for example. A screenshot of AS SSD would be nice too, because it includes alignment information and driver information in the top left corner.

You speak about write cache, but you do not mention volume write-back cache. Is that enabled in the Intel RST driver utility? If not, parity RAIDs would be very slow because the disks will seek all the time. They might also wear quicker because you're letting them seek all the time. And it would explain the low performance.

Without any measured data, it is impossible to help you with performance issues. So always include data allowing others to help you with your issue is probably good advice. ;-)

 

[mrpiggy]

Did you try 4x2 like it was originally was? Might simply be a scaling issue. The controller might just not be able to handle the concurrency load of more than 4 drives in RAID 5 well. not saying that's the problem, but it would be something to check to see if the original configuration runs the same still.

 

[darkfalz]

Intel RST. Yes, it's "crappy software onboard" and so on, but it worked brilliantly with my last array which is why I am so annoyed that after spending this much on a new array, with several generations newer HDDs, the performance sucks...

The strange thing is I get identical results with all caching modes (off, write through, write back ie. write cache and buffer flushing disabled). 26 MB/sec writes. Have tried restarts between changing settings and no difference. CPU usage is virtually zero.

Differences between last array and this one are

5x4TB vs 4x2TB
4k sectors vs 512
1 disk in on Sata 6g other 4 on 3g, vs last with all on 3g

Running Windows 7 64bit. Tried with latest Intel RST drivers and no change.

Am at work now but will experiment with 4 drives instead of 5 (hope this isn't it, as losing 4 TB storage this way, but I suppose this gives me a spare on-hand) and different stripe/cluster sizes.

 

[darkfalz]

This may have been resolved by going to a lower stripe size, but this terribe thing called going to work interrupted me before I could do further testing

 

[darkfalz]

Spot the odd one out....

http://i.imgur.com/qwJBjSv.png

Nice job Intel.