mfi driver performance

Hi!

We’re testing a new Intel S2600GL-based server with their recommended RAID adapter ("Intel(R) Integrated RAID Module RMS25CB080”) which is identified as

mfi0: <ThunderBolt> port 0x2000-0x20ff mem 0xd0c60000-0xd0c63fff,0xd0c00000-0xd0c3ffff irq 34 at device 0.0 on pci5
mfi0: Using MSI
mfi0: Megaraid SAS driver Ver 4.23 
mfi0: MaxCmd = 3f0 MaxSgl = 46 state = b75003f0 

or

mfi0_at_pci0:5:0:0:        class=0x010400 card=0x35138086 chip=0x005b1000 rev=0x03 hdr=0x00
    vendor     = 'LSI Logic / Symbios Logic'
    device     = 'MegaRAID SAS 2208 [Thunderbolt]'
    class      = mass storage
    subclass   = RAID

and seems to be doing quite well.

As long as it isn’t used…

When the system is getting a bit more IO load it is getting close to unusable as soon as there are a few writes (independent of configuration, it is even sucking  as a glorified S-ATA controller). Equipping it with an older (unsupported) controller like an SRCSASRB
(mfi0_at_pci0:10:0:0:       class=0x010400 card=0x100a8086 chip=0x00601000 rev=0x04 hdr=0x00
    vendor     = 'LSI Logic / Symbios Logic'
    device     = 'MegaRAID SAS 1078'
    class      = mass storage
    subclass   = RAID) solves the problem but won’t make Intel’s support happy.

Has anybody similar experiences with the mfi driver? Any good ideas besides running an unsupported configuration?


Achim