Optimize Mac Pro hardware RAID card

[mcmartin]

Hi everyone

 

I am using the Apple RAID card with 4 internal drives (WD5001ABYS, Western Digital 500 GB, SATA II, Raid Edition 2/RE2). I need this system for medical research purposes to analyze videos and images. My quick summary: the system is by far faster (my everyday experience) than my previous computer (G5). Also system startup (Mac OS 10.5 Leopard) from the RAID works nicely. The set up with the RAID utility was extremely easy. Further I first tried a 0+1 setting then switching to a RAID 0 was easy. Some first movie analysis also worked well. So overall everything works.

 

However, I wonder if I could optimize performance. Here is why: Apple claims that the RAID card reaches a transfer speed of up to 304 MB/sec (http://www.apple.com/macpro/expansion.html). Now my hard drives are supposed to maintain a sustained transfer speed of 85 MB/sec (Western Digital claim, buffer to disc; http://www.westerndigital.com/en/products/...sp?DriveID=331). My actual transfer speed are far below: at the max 100 MB/sec (Xbench, uncached write, 4K blocks), but my RAID system drops to poor 21 MB/sec (Xbench, uncached write 256 kB blocks). 4 uptodate hard drives in a RAID 0 should come up with more than 100 MB/sec ???

 

And: from the beginning I received the RAID utility error message "Write caches deactivated"/"Battery missing". According to my vendor a missing battery is due to the fact that I dont have an external additional power supply, mmh??

 

Can anyone explain the error message or the sluggish performance?

 

Thanks

Martin

[shoarthing]

Hi everyone

 

I am using the Apple RAID card with 4 internal drives (WD5001ABYS, Western Digital 500 GB, SATA II, Raid Edition 2/RE2). I need this system for medical research purposes to analyze videos and images. My quick summary: the system is by far faster (my everyday experience) than my previous computer (G5). Also system startup (Mac OS 10.5 Leopard) from the RAID works nicely. The set up with the RAID utility was extremely easy. Further I first tried a 0+1 setting then switching to a RAID 0 was easy. Some first movie analysis also worked well. So overall everything works.

 

However, I wonder if I could optimize performance. Here is why: Apple claims that the RAID card reaches a transfer speed of up to 304 MB/sec (http://www.apple.com/macpro/expansion.html). Now my hard drives are supposed to maintain a sustained transfer speed of 85 MB/sec (Western Digital claim, buffer to disc; http://www.westerndigital.com/en/products/...sp?DriveID=331). My actual transfer speed are far below: at the max 100 MB/sec (Xbench, uncached write, 4K blocks), but my RAID system drops to poor 21 MB/sec (Xbench, uncached write 256 kB blocks). 4 uptodate hard drives in a RAID 0 should come up with more than 100 MB/sec ???

 

And: from the beginning I received the RAID utility error message "Write caches deactivated"/"Battery missing". According to my vendor a missing battery is due to the fact that I dont have an external additional power supply, mmh??

 

Can anyone explain the error message or the sluggish performance?

 

Thanks

Martin

. . . replying to your points in the way you've phrased them is not simple:

 

1) If as I suspect this RAID host is an Apple-badged &/or modded LSI host, then, yes, not having the battery-pack will seriously affect performance, since (from memory of various LSI hosts) write-back is disabled with no BBU. Look here for a simple overview of write-through/write-back performance effects.

 

2) You don't say which motherboard you're using, nor what PCIe settings this motherboard allows: consumer-level boards can have performance issues with 8x (?) PCIe RAID-hosts.

 

3) HDDs vary enormously in their optimisation for various hardware RAID-hosts - worthwhile to establish the exact make/model of your Apple-badged host.

 

4) Xbench is not a good guide to RAID-host performance - isn't there an OSX port of IOMeter?

 

[Edit] . . looks like you'll have to compile IOMeter from source.

[mcmartin]

Hi shoarthing

To 1) thanks for the link to RAID performance effects. Other RAID cards seem to have a very nice performance-the test is from 2005 though. I couldnt find further specs on my Apple RAID card. What is an LSI host?

To 2) My motherboard: standard off-the-shelf Apple Mac Pro desktop computer (2x duo core 2.6 GHz): see http://www.apple.com/macpro/specs.html

To 3) how can I find out about my host?

To 4) I found only IOMeter for Linux, Win but not Mac. Please post link if available.

Martin