LSI 6GB/s RAID6 Performance Issues

[T_Minus]

Even with CacheCade SSD Cache the performance is terrible.

Screen clip

Be sure to scroll, and read notes at bottom it outlines what I changed between tests.

CacheCade should be worth it! I'm not sure why it's not showing CacheCade 2.0 either... any ideas?

What are proper/optimal settings for a RAID6 config? Read Ahead? Writ back? Direct IO, etc....

I'd like to use CacheCade as it seems to work great when I google, and read reviews here but wow it didn't do anything for me. Possibly due to version 1.0 vs 2.0? Not 100%.

 

[T_Minus]

As you can see the S3500 appears to be operating at the Intel specs (or rather very close) based on their IOPs if memory serves me. So I'm not sure why when cached it doesn't benchmark good, other than possibly the benchmark utility doesn't make use of the cache by writing new data for each test and then reading?

I wonder if there's a different / better way to benchmark w/Cachecade/

 

[Mr. F]

Do you have a cache on the LSI card?

 

[T_Minus]

Yes, the onboard LSI 2208 cache is 1GB, tests were all done with 4GB of data as to avoid RAID CARD cache-hits only.

 

[azev]

Have you try enabling write back on the array ? I notice the difference between write back and write through is very significant even with cachecade on.
Anyway mine is setup with Writeback with BBu, no read ahead, direct io, and disk cache policy enabled.
I think the performance on mine is pretty good, especially when the cache is warm.

 

[T_Minus]

Currently using/testing:

Strip Size: 64KB & 512KB tested.
(RAID6 for NAS duty, streaming videos, mp3s, etc... it has small files like "my Docs" but more for backup than linked to desktop. Not too sure optimal size if I use CacheCade + SSD though.)

Read Policy: No Read Ahead
Write Policy: Always write back.
I/O Policy: Direct IO
Disk Cache Policy: Disabled

Thank you for the input.

 

[T_Minus]

Have you try enabling write back on the array ? I notice the difference between write back and write through is very significant even with cachecade on.
Anyway mine is setup with Writeback with BBu, no read ahead, direct io, and disk cache policy enabled.
I think the performance on mine is pretty good, especially when the cache is warm.

If you have time can you do a benchmark and also let me know which drives you're using, controller, software/hardware raid, cache, etc...

 

[T_Minus]

Caschade 2.0:
"Think of the cachecade 2.0 write functionality as just being a 2nd level write cache that gets migrated to spinning disk as io load allows. Writes go to nvram, then to ssd, then to disk -- if write cache is enabled."
Source: Dell/LSI CacheCade - Any Experiences? - Ars Technica OpenForum (ANOTHER FORUM)

 

[azev]

here's my anvil test result, mind you the same drive is currently running about 20vm mounted via iscsi.

This is Raid6 with 14x 2Tb combination of Hitachi & Toshiba drive. Cachecade SSD is HUSSL4020ASS600... all drive connected in a supermicro chassis with sas2 expander.

 

[T_Minus]

What about your:

Strip Size:


Read Policy:
Write Policy:
I/O Policy:
Disk Cache Policy:
(Since I had disk cache policy disabled, I wonder if that messes with CacheCade, not sure on that.)


Yours looks good with the Cachecade, and more along what I'd expect.

 

[azev]

Strip Size: 256K
Read Policy: No read Ahead
Write Policy: Writeback with BBU
I/O Policy: Direct IO
Disk Cache Policy: Enabled

 

[ninja6o4]

Did you ever solve your RAID6 performance issues? I'm running into something similar myself and will be doing some investigating.