Re: Extremely slow write speeds to disk : FreeBSD 7.1 and Dell SAS 6/iR Adapter

[Tom Judge]

Sebastiaan van Erk wrote:
Dieter wrote:
But the issue is that writing to disk is extremely slow...i.e. 14Mb 
per
second....

If I install any other linux distribution, like CentOS, write speek is
the way it should be..it averages around 190Mb+ per second

I was hoping if it were at all possible for you to assist me in with a
later RAID Controller Driver for the SAS 6/iR Adapter
      
Try:
hw.mpt.enable_sata_wc=1
in /boot/loader.conf and reboot.

Assuming you are using SATA drives, the write cache is disabled by 
default. This reenables it. The mpt manpage holds more information.
    

Just keep in mind that turning the disk's write cache on puts your
data at risk.  :-(

The correct solution is NCQ.
Just wondering, if you have a battery on your RAID array, is this a 
problem? Wouldn't the cache get written anyway in case of a crash?

Regards,
Sebastiaan
Hi,

hw.mpt.enable_sata_wc tunable enables the on disk write cache not the 
controller write cache.

Tom
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