Date: Fri, 04 Sep 1998 22:17:51 -0500 From: David Kelly <dkelly@hiwaay.net> To: freebsd-stable@FreeBSD.ORG Subject: Re: 8mm tape block size max - changed? Message-ID: <199809050317.WAA20987@nospam.hiwaay.net> In-Reply-To: Message from "Chad R. Larson" <chad@freebie.dcfinc.com> of "Fri, 04 Sep 1998 11:44:21 PDT." <199809041844.LAA15768@freebie.dcfinc.com>
next in thread | previous in thread | raw e-mail | index | archive | help
"Chad R. Larson" writes:
> Or,
>
> dd if=/dev/tape of=/tmp/junk bs=64k count=1
> ls -l /tmp/junk
>
> should tell you the size of the tape blocks.
Agreed. It *should*. But for some reason it doesn't anymore.
n4hhe: {553} tar -cvb 20 gifs
gifs/
gifs/cycle_large.gif
gifs/title_bottom.gif
[...]
n4hhe: {554} dd if=/dev/rst0 bs=64k of=/dev/null count=1
1+0 records in
1+0 records out
65536 bytes transferred in 2.138313 secs (30648 bytes/sec)
n4hhe: {555} tcopy
file 0: block size 65536: records 0 to 7
file 0: block size 43008: record 7
file 0: eof after 8 records: 501760 bytes
eot
total length: 501760 bytes
n4hhe: {556}
You'll notice 501760 is 49 * 10240 and the last block came up short of
64k. I believe tar correctly wrote the tape with 10k blocksize but the
kernel is (incorrectly) combining multiple blocks to fill a single read.
I don't believe this has always been the case.
n4hhe: {559} uname -a
FreeBSD n4hhe.ampr.org 2.2.7-STABLE FreeBSD 2.2.7-STABLE #0: Sun Jul 26 21:19:55 CDT 1998 root@n4hhe.ampr.org:/usr/src/sys/compile/PPRO200 i386
n4hhe: {560} mt stat
Present Mode: Density = QIC-150 Blocksize = 512 bytes
---------available modes---------
Mode 0: Density = 0x00 Blocksize variable
Mode 1: Density = X3.136-1986 Blocksize = 512 bytes
Mode 2: Density = X3.39-1986 Blocksize variable
Mode 3: Density = X3.54-1986 Blocksize variable
n4hhe: {561}
--
David Kelly N4HHE, dkelly@nospam.hiwaay.net
=====================================================================
The human mind ordinarily operates at only ten percent of its
capacity -- the rest is overhead for the operating system.
To Unsubscribe: send mail to majordomo@FreeBSD.org
with "unsubscribe freebsd-stable" in the body of the message
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?199809050317.WAA20987>