Slow write to LSI Logic / Symbios Logic SAS1068E

i had to install system [ Debian that is ] on HP DL120G5 server.

all went fine but it turned out write on the disk drives connected to onboard sas/sata controller was horrible. apparently other people experienced similar issue – this controller by default does not enable write cache. but solutions found on the web did not really work for me – they advices to enable write cache in the raid settings; i’ve run:

cd /usr/local/src
wget ftp://ftp.lsil.com/HostAdapterDrivers/linux/lsiutil/lsiutil.tar.gz
tar -zxvf lsiutil.tar.gz
cd lsiutil
make
./lsiutil

but when i tried to go into RAID actions i got:

RAID actions menu, select an option:  [1-99 or e/p/w or 0 to quit] 21
No active physical disks

although disks were connected to LSI controller:

Main menu, select an option:  [1-99 or e/p/w or 0 to quit] 42
/proc/mpt/ioc0 is SCSI host 4
 B___T___L  Type       Operating System Device Name
 0   1   0  Disk       /dev/sda    [4:0:0:0]
 0   2   0  Disk       /dev/sdb    [4:0:1:0]

but.. setting Write cache in ‘Change IO Unit settings’ of expert mode:

Main menu, select an option:  [1-99 or e/p/w or 0 to quit] e
14.  Change IO Unit settings (multi-pathing, queuing, caching)
Main menu, select an option:  [1-99 or e/p/w or 0 to quit] 14
Multi-pathing:  [0=Disabled, 1=Enabled, default is 0] 0
SATA Native Command Queuing:  [0=Disabled, 1=Enabled, default is 0] 0
SATA Write Caching:  [0=Disabled, 1=Enabled, default is 1] 1

and rebooting the server did the trick.

before in dmesg i saw:

sd 4:0:0:0: [sda] Write cache: disabled, read cache: enabled, doesn't support DPO or FUA

now i have:

sd 4:0:0:0: [sda] Write cache: enabled, read cache: enabled, doesn't support DPO or FUA

and

time (dd if=/dev/zero of=bigfile count=1024 bs=1M; sync)

gives me reasonable 65MB/sec instead of miserable 13.

maybe this post will help someone…