SAS5IR performance issue with Dell 860

[韓家標 Bill Hacker]

Espen Tagestad wrote:
> Hi,
> 
> We recently bought 3 new Dell 860 servers with the onboard SAS5/IR SATA 
> RAID-controller. They seem to be quite well spec'ed servers with 
> management and everything - but I am experiencing av major performance 
> issue with the disc i/o. On write I get at max 7-8MB/sec, while read 
> gives a bit more (11MB/sec). I tried first with 6.2-RELEASE, and then 
> upgraded to 6.3-PRERELEASE without any better results.
> 
> I am aware of some discussion around this issue on these two maillists 
> in the spring earlier on this year, but I have not been able to find any 
> good resolution. My old firewall/router at home equipped with a 733Mhz 
> Pentium 3 processor and a old 40GB IDE harddrive made around year 2001 
> performe better. Is there anybody out there with the same problem who 
> has solved this issue? Could it be that this is solved in 7.0?
> 
> Thanks in advance.
> 

You haven't indicated what drives are on that controller, or how (RAID?) 
arranged.,, what sort of on-drive or on-controller cahce and policy.

Nor how you measured the '..performs better', which a single <anything> can 
often do compared to several of the possible RAID configurations.

Otherwise, those are not actually 'bad' numbers for sustained I/O - especially 
if anything-at-all is going on at the same time that needs to intervene and move 
the r/w heads 'elsewhere' - however briefly.

More info?

Bill