Date: Fri, 3 May 1996 15:28:29 -0400 (EDT) From: Eric Chet <ec0@s1.GANet.NET> To: Satoshi Asami <asami@CS.Berkeley.EDU> Cc: dkelly@HiWAAY.net, freebsd-scsi@FreeBSD.ORG Subject: Re: Buffered Writes? Message-ID: <Pine.SOL.3.91.960503152557.22613A-100000@s1> In-Reply-To: <199605012312.QAA05975@sunrise.cs.berkeley.edu>
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On Wed, 1 May 1996, Satoshi Asami wrote: > * 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 Hello Does anybody know how to or have a utility to turn on the write cache on a barracuda? I have a wide barracuda on a NCR 825 and would like to see if there is any performance difference. Peace, Eric
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