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

Dieter freebsd at sopwith.solgatos.com
Fri Feb 13 23:08:57 PST 2009

> > 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.

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