Dell SAS5 Performance Issue

[Ivan Voras]

Richard Tector wrote:
> I'm suffering from very slow write performance on a Dell PowerEdge 860
> with the SAS5/IR controller (mpt driver) running either 6.2-RELEASE or
> 6.2-STABLE with sources from yesterday. The controller hosts 2 Western
> Digital 320GB SATA disks in a RAID1 configuration.
> Reads approach 65MB/s however writes appear extremely slow, in the
> region of 6-7MB/s with a dd and a blocksize of 1MB all the way down to
> about 300KB/s while extracting a ports snapshot.
> 
> It was suggested to me that perhaps write caching has been disabled on
> the controller however no options exist within the BIOS configuration to
> view/adjust *any* caching options.

You looked in the controller's BIOS, not motherboard's, right? There
should be at least a "write through" vs "write back" switch...
If you don't have a battery for the SAS controller, get one.

> Has anyone else experienced this issue? 

No, but can you post the relevant bits for the controller from dmesg?


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