Dell SAS5 Performance Issue

[Richard Tector]

Ivan Voras wrote:
> 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?
Indeed I did.
> There should be at least a "write through" vs "write back" switch...
Correct, there should be options, but there aren't. The controller BIOS has very few options at all in fact.

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

mpt0: <LSILogic SAS/SATA Adapter> port 0xec00-0xecff mem 
0xfe9fc000-0xfe9fffff,0xfe9e0000-0xfe9effff irq 16 at device 8.0 on pci2
mpt0: [GIANT-LOCKED]
mpt0: MPI Version=1.5.12.0
mpt0: mpt_cam_event: 0x16
mpt0: Unhandled Event Notify Frame. Event 0x16 (ACK not required).
mpt0: mpt_cam_event: 0x12
mpt0: Unhandled Event Notify Frame. Event 0x12 (ACK not required).
mpt0: mpt_cam_event: 0x12
mpt0: Unhandled Event Notify Frame. Event 0x12 (ACK not required).
mpt0: mpt_cam_event: 0x16
mpt0: Unhandled Event Notify Frame. Event 0x16 (ACK not required).
[...snip...]
da0 at mpt0 bus 0 target 0 lun 0
da0: <Dell VIRTUAL DISK 1028> Fixed Direct Access SCSI-5 device
da0: 300.000MB/s transfers, Tagged Queueing Enabled
da0: 305175MB (624998400 512 byte sectors: 255H 63S/T 38904C)

Regards,

Richard