From owner-freebsd-hackers Sun Jun 4 19:55:16 1995 Return-Path: hackers-owner Received: (from majordom@localhost) by freefall.cdrom.com (8.6.10/8.6.6) id TAA06973 for hackers-outgoing; Sun, 4 Jun 1995 19:55:16 -0700 Received: from mpp.com ([204.157.201.242]) by freefall.cdrom.com (8.6.10/8.6.6) with ESMTP id TAA06961 for ; Sun, 4 Jun 1995 19:55:09 -0700 Received: (from mpp@localhost) by mpp.com (8.6.11/8.6.9) id VAA01688 for hackers@freebsd.org; Sun, 4 Jun 1995 21:54:24 -0500 From: Mike Pritchard Message-Id: <199506050254.VAA01688@mpp.com> Subject: why won't my tape drive keep streaming? To: hackers@freebsd.org Date: Sun, 4 Jun 1995 21:54:23 -0500 (CDT) X-Mailer: ELM [version 2.4 PL24] MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Content-Length: 1881 Sender: hackers-owner@freebsd.org Precedence: bulk I have an Archive 2150S SCSI tape drive attached to An Adaptec 2842VL controller. This drive is capable of writing 6MB+ per minute, but I rarely see that under FreeBSD (running -current). Often the drive will start out streaming, writing 5.5MB/min - 6MB/min. After a while, and for no apparent reason, the drive will stop streaming, and throughput drops down to as bad as 1MB/min - 3MB/min. This happens even on a totally idle machine with just the test program running. I've also tried several different tapes, so I don't think it is a media problem. Plus, the drive will stream with a tar program that supports drive under DOS. Usually when this happens the drive won't start streaming again until the program stops and closes/re-opens the tape device and starts writing again (although the test I have running right now seems to have started streaming again after dropping to start/stop mode for about 15 megabytes, but that is unusual). I've been running these tests with nothing else running on the machine, and it is doing all of the tape writes directly from memory - no disk access is involved. I've tried writes with sizes ranging from 512 bytes at a time all the way up to 10 megabytes. Writes of size 10240 bytes seem work the best, but even those usually fall off after a while and stop streaming. Has anyone else seen this problem with this tape drive, or have any ideas as to what the problem might be? Reads from the tape drive don't seem to suffer from this problem. Basically the guts of the test program looks like: dev = argv[1]; bsize = atol(argv[2]); bcount = atol(argv[3]); buf = malloc(bsize)); fd = open(dev, O_RDWR)); for (i = 0; i < bcount; i++) { if (write(fd, buf, bsize) <= 0) { perror("write"); exit(1); } } -- Mike Pritchard mpp@legarto.minn.net "Go that way. Really fast. If something gets in your way, turn"