Slow throughput on Intel SRCS28X RAID Ctrlr

[dthede]

Windows Server 2003/XP Pro environment.
This RAID controller card is in a 133MHz slot in an SE7520BD2 Intel logic board, controlling 6 Maxtor 7Y250M0 1.5Gb/s drives (Maxline II). The ctrlr has 128MB RAM on it, supporting a RAID5 config. Not using optional on-card battery backup.

While the drives are now obsolete, they are not too shabby. However, the throughput for this array has been worse than disappointing from day one.

Installation directions recommends disabling the on-disk cache (set to WRITE THROUGH) which has been done.

(1) Can anyone indicate the reality of enabling the on-disk cache based on their (similar) experience?
(2) Approx. 6MB/sec writing speed is measured over a sustained 300GB copy, vs. 46 MB/sec to a standard mirrored drive pair (both across the Gb network); copy from the same source. What sort of real-world write speeds are others typically getting?
(3) copies from one (FW800) external drive to another on this "all-Intel" box are, again, _much_ faster than even the 46MB/sec mentioned above. Intel and (some of) its VARs have nothing helpful to say.

 

[technome]

Not familiar with this particular controller, but disabling "write back" on every raid adapter I have used for raid 5 absolutely CRIPPLES throughput. As to data safety, in years past, 1990-1994, I was running raid with write back enabled without battery backed cache at a number of clients with UPS units( as were many others), never had data loss.
I would not do this at this point !!!; at that time, in small businesses, little flowed to the disks...battery backed cards were expensive.
If you have a UPS, you would be fairly safe, as long as writes are not taking place, when the UPS gives out.

I will not guess as to the throughput you should be getting with this disk system, as I only use SAS or SCSI for raids, but I used to get 6 meg/sec back in the early 90s.



........................................
Chernobyl disaster..a must see pictorial

http://www.kiddofspeed.com/default.htm

 

[dthede]

... but I used to get 6 meg/sec back in the early 90s."

Hence the request for help. And, exactly my thought as I reminisced about a Compaq Proliant from that period, etc.

Please note, however, that the issue is one of interaction between two caches: one on the RAID controller, and one on each disk. Note that cacheing on the _controller_ is not disabled (that's set to WRITE BACK). It's the cache on the _hard drives_ which is disabled in/by the RAID setup. My question was, should the cacheing on the hard disks be enabled - contrary to installation notes advice.

System is on a large capacity UPS, hence idea of foregoing the battery backed ctrlr. If we get the throughput I'd expect, then battery backup is "ipso facto" in the budget. Intel's diplomatically stated warning is to the effect that throughput can be negatively impacted. Right.

 

[technome]

Sorry for the lack of my reading ability...

"My question was, should the cacheing on the hard disks be enabled - contrary to installation notes advice."

I have benchmarked with the drive cache enabled/disabled, on a few different controllers, if the raid adapter allowed it or I could bypass the defaults. In almost all tests, with different manufacturers/model drives, it made NO discernible difference in benchmark tests (which surprised me at first); in a couple tested arrays a slight negative or positive throughput resulted. A poster at CPU.com stated he did see a notable positive difference in performance on his array...guessing, possibly due to the drive manufacturer's cache programming.



........................................
Chernobyl disaster..a must see pictorial

http://www.kiddofspeed.com/default.htm