Date: Wed, 1 May 1996 16:12:48 -0700 From: asami@cs.berkeley.edu (Satoshi Asami) To: dkelly@hiwaay.net Cc: freebsd-scsi@freebsd.org Subject: Re: Buffered Writes? Message-ID: <199605012312.QAA05975@sunrise.cs.berkeley.edu> In-Reply-To: <v02140b05adac79b189ad@[206.104.23.160]> (dkelly@hiwaay.net)
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* How do I querry (and maybe enable) my hard drives for buffered writes? I
* have (2) supposedly identical ST3610N Seagate 500M drives and the one on
* SCSI ID #0 seems to run at half the thruput of the other on ID #1. I'm
* guessing one had internal caching enabled. The answer is mostly acedemic
* now as those drives are elsewhere, replaced with an ST32550N, but now I'd
* like to know more about how my Barracuda is configured. Studying scsi(8)
* suggests that is where the key is but at this time I know enough to know I
* shouldn't go playing with scsi(8) using random commands.
*
* System is a NexGen PCI-90 with Adaptec 2940.
Yes, the Barracuda comes without the write cache enabled. However, by
turning on the tagged queuing (options AHC_TAGENABLE), we got the
sequential write speed to get very close to the read speed:
write read
without tag 3.6 6.9
with tag 6.2 7.9
So we haven't actually looked into how to enable the write cache.
Please let me know if you find something interesting.
Satoshi
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