From owner-freebsd-current Tue Dec 21 7: 2:38 1999 Delivered-To: freebsd-current@freebsd.org Received: from uni4nn.gn.iaf.nl (osmium.gn.iaf.nl [193.67.144.12]) by hub.freebsd.org (Postfix) with ESMTP id F2CC515458 for ; Tue, 21 Dec 1999 07:02:34 -0800 (PST) (envelope-from wilko@yedi.iaf.nl) Received: from yedi.iaf.nl (uucp@localhost) by uni4nn.gn.iaf.nl (8.9.2/8.9.2) with UUCP id PAA18783; Tue, 21 Dec 1999 15:01:44 +0100 (MET) Received: (from wilko@localhost) by yedi.iaf.nl (8.9.3/8.9.3) id KAA52343; Tue, 21 Dec 1999 10:07:28 +0100 (CET) (envelope-from wilko) Date: Tue, 21 Dec 1999 10:07:28 +0100 From: Wilko Bulte To: Matthew Dillon Cc: Greg Lehey , FreeBSD current users Subject: Re: Recent current hangs frequently for 1 to 2 seconds. Message-ID: <19991221100727.A52224@yedi.iaf.nl> References: <19991219143759.C465@freebie.lemis.com> <199912190416.UAA01125@apollo.backplane.com> <19991221095213.L440@freebie.lemis.com> <199912210019.QAA62510@apollo.backplane.com> <19991221110148.N440@freebie.lemis.com> <199912210108.RAA62736@apollo.backplane.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-Mailer: Mutt 1.0i In-Reply-To: <199912210108.RAA62736@apollo.backplane.com>; from dillon@apollo.backplane.com on Mon, Dec 20, 1999 at 05:08:27PM -0800 X-OS: FreeBSD yedi.iaf.nl 3.3-STABLE FreeBSD 3.3-STABLE X-PGP: finger wilko@freebsd.org Sender: owner-freebsd-current@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG On Mon, Dec 20, 1999 at 05:08:27PM -0800, Matthew Dillon wrote: > :It's possible you might be on to something. I've been running iostat > :at 1 second intervals, and during the last hang I saw: > : > : tty ad2 da1 sa1 cpu > : tin tout KB/t tps MB/s KB/t tps MB/s KB/t tps MB/s us ni sy in id > : 36 142 7.75 95 0.72 0.00 0.00 0 10.00 27 0.27 29 0 9 1 61 > : 21 142 8.00 69 0.54 0.00 0.00 0 0.00 0 0.00 6 0 1 0 93 > : 37 143 8.00 44 0.34 0.00 8.00 3 0.00 0 0.00 5 0 1 1 94 > : 41 142 1.76 106 0.18 16.00 5.25 4 10.00 14 0.13 24 0 18 0 57 > : 15 143 1.98 87 0.17 0.00 0.00 0 10.00 16 0.15 30 0 15 2 54 > : > :Note that the stop in tape activity corresponds with a start in disk > :activity. I'll keep an eye on that and see if it looks the same the > :next time. > > Tape drives may: > > * Not support disconnection (the SCSI bus is locked through the entire > write sequence), or only partially support disconnection but run the > bus so slowly that other devices are left out in the cold. DLT drives do support disconnect/reconnect. > * Implement a crappy SCSI command stack that breaks down when So do may disks :) > higher-speed operations are running on the same bus (e.g. the disks > with their higher synchronous transfer rates). > > * Not properly terminate the SCSI bus (especially when mixing > bus architectures. For example, a tape drive may only > half-terminate a wide SCSI bus. Never use a tape drive to > terminate a SCSI bus, not even an older SCSI bus. As has been discussed many times already: use external terminators attached to the cable. SCSI termination is not difficult, it is just made that way by some :( > * Introduce too much noise onto the SCSI bus due to bad design. Does not apply to DLT drives that I've seen. A more interesting question would be if the DLT drive has a more or less recent firmware loaded. -- Wilko Bulte Arnhem, The Netherlands - The FreeBSD Project WWW : http://www.tcja.nl http://www.freebsd.org To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message