IBM blade server abysmal disk write performances

[Karim Fodil-Lemelin]

On 18/01/2013 10:16 AM, Mark Felder wrote:
> On Thu, 17 Jan 2013 16:12:17 -0600, Karim Fodil-Lemelin 
> <fodillemlinkarim at gmail.com> wrote:
>
>> "SAS controllers may connect to SATA devices, either directly 
>> connected using native SATA protocol or through SAS expanders using 
>> SATA Tunneled Protocol (STP)."
>>  The systems is currently put in place using SATA instead of SAS 
>> although its using the same interface and backplane connectors and 
>> the drives (SATA) show as da0 in BSD _but_ with the SATA drive we get 
>> *much* better performances. I am thinking that something fancy in 
>> that SAS drive is not being handled correctly by the FreeBSD driver. 
>> I am planning to revisit the SAS drive issue at a later point 
>> (sometimes next week).
>
> Your SATA drives are connected directly not with an interposer such as 
> the LSISS9252, correct? If so, this might be the cause of your 
> problems. Mixing SAS and SATA drives is known to cause serious 
> performance issues for almost every 
> JBOD/controller/expander/what-have-you. Change your configuration so 
> there is only one protocol being spoken on the bus (SAS) by putting 
> your SATA drives behind interposers which translate SAS to SATA just 
> before the disk. This will solve many problems.
Not sure what you mean by this but isn't the mpt detecting an interposer 
in this line:

mpt0: <LSILogic SAS/SATA Adapter> port 0x1000-0x10ff mem 
0x99910000-0x99913fff,0x99900000-0x9990ffff irq 28 at device 0.0 on pci11
mpt0: MPI Version=1.5.20.0
mpt0: Capabilities: ( RAID-0 RAID-1E RAID-1 )
mpt0: 0 Active Volumes (2 Max)
mpt0: 0 Hidden Drive Members (14 Max)

Also please not SATA speed in that same hardware setup works just fine. 
In any case I will have a look.

Thanks,

Karim.