Date: Sat, 20 Feb 1999 12:59:05 +0100 From: Paul van der Zwan <paulz@trantor.xs4all.nl> To: "Kenneth D. Merry" <ken@plutotech.com> Cc: freebsd-current@FreeBSD.ORG Subject: Re: Slow seq. write on Seagate ST36530N Message-ID: <199902201159.MAA01220@trantor.xs4all.nl> In-Reply-To: Your message of "Fri, 19 Feb 1999 14:15:52 MST." <199902192115.OAA04024@panzer.plutotech.com>
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> Paul van der Zwan wrote... > > > > I am having some performance problems on my -current ( update last weekend) > > I hooked up a new Seagate ST36530N yesterday ( connected to an Adaptec 2940U) > Andreas Klemm has had similar trouble, as he pointed out. > Can you check and see whether or not you have write caching turned on for > your disk? I have seen problems with sequential writes that appear to be > caused by conflicts between FreeBSD's caching policy and disk caching > policies. These problems often go away when you disable write caching on a > disk. > > The Write Cache Enable (WCE) bit is in mode page 8. To check it: > > camcontrol modepage -n da -u 1 -v -m 8 > > To edit the mode page: > > camcontrol modepage -n da -u 1 -v -m 8 -e > > Let me know whether that affects the problem at all. This did not improve anything , but I think I have found the couse. In that modepage there is a DISC value which was 0 on the IBM and 1 on the Seagate. I remembered a ' Enable disconnect' option in the Adaptec 2940 bios, setting this to 'off' for both harddisks led to a huge performance increase on the Seagate. If I also enable Ultra mode iozone write goes from 1.5 MB/s to 12 MB/s ( a factor of 8 !!!). Paul -- Paul van der Zwan paulz @ trantor.xs4all.nl "I think I'll move to theory, everything works in theory..." To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message
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