Date: Sat, 29 Oct 2011 05:01:25 -0600 From: freebsd-questions@phillipsjk.ca To: freebsd-questions@freebsd.org Subject: Abstraction leakage burning test DVD+R Message-ID: <20111029110125.GA5140@workhorse.inet>
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[-- Attachment #1 --] Hello, After my dump/restore test failed back in May of 2010[1], I finally got around to burning a test DVD after installing about 2.5 inches of semi-rigid foam under the machine to dampen any local vibration. In designing the test, I was under the mistaken impression that buffer under-runs would reduce the amount of space for writing. Apparently, DVD+R media supports loss-less linking[2]. Test Procedure (using ATAPI interface, rather than the newer ATAPI/CAM interface). The man pages do not imply any major differences for this test. The drive in question is a LG drive with the SuperMulti logo. Test procedure: 1.# mkfifo auxout aux45G 2. In other terminals: # cat auxout | md5 # dd if=aux45G count=2197266 bs=2048 | md5 3. Write test disk: # dd if=/dev/urandom bs=2048 count=2295104 | \ tee auxout aux45G | dd of=/dev/acd0 bs=2048 Error: dd:/dev/acd0: Input/output error 679+0 records in 678+0 records out 1388544 bytes transferred in 80.97 seconds (step 4 not completed due to premature burn failure after 684 blocks, 80 seconds (from 'dd if=aux45G'...) (15743 bytes/sec)) Drive spun up at least twice during this time. 4. Read test (in another term 'cat aux45G | md5') # dd if=/dev/acd0 bs=2048 count=2295104 | tee aux45G | md5 Questions: Currently, the drive is locked. Before forcefully ejecting it and risking an new disk, I want to know what may have gone wrong. Was I expecting too much of FreeBSD on old hardware? The hardware is a Pentium-II desktop machine with 256MB of RAM, with a Promise ATA100 controller card. An extra-long 80-wire cable is in use (to ad4). acd0: DVDR <HL-DT-STDVD-RAM GSA-H55N/1.03> at ata-1-master UDMA33 ad4: 78167MB <Maxtor 6Y080L0 YAR41WB0> at ata-2-master UDMA100 dd if=/dev/urandom of=/home/test Wrote at 4485315 bytes/second: faster than I was expecting (based on linux's slow urandom function), but still slow enough to cause buffer under-runs. So the second question is: do I have to do anything special to enable buffer underrun protection? (with DVD+R's lossless linking feature, no data should be lost.) How important is running ATAPI/CAM? Obviously DVD burning was happening before the release of version 8, as far as I know. If running out of data is supposed to be abstracted away, did I find a bug that only shows up on old hardware or heavy load? (Or possibly drive firmware bug?) Regards, James Phillips # uname -a FreeBSD dusty.inet 8.0-RELEASE FreeBSD 8.0-RELEASE #0: Sat Nov 21 15:48:17 UTC 2009 root@almeida.cse.buffalo.edu:/usr/obj/usr/src/sys/GENERIC i386 [1] dump/restore (to DVD+R) test failure http://docs.freebsd.org/cgi/getmsg.cgi?fetch=290415+0+archive/2010/freebsd-questions/20100530.freebsd-questions [2] Why DVD+R(W) is superior to DVD-R(W) http://www.myce.com/article/Why-DVDRW-is-superior-to-DVD-RW-203/ PS: is signing messages on the mailing list a faux-pas? -- OpenPGP Public Key: http://phillipsjk.ca/signature0611.txt [-- Attachment #2 --] -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.6 (GNU/Linux) iD8DBQFOq90FPPYMXhz9onsRAoymAJ4mf2X8f1Z88150dkoNuU1w5RpfkgCdHiih FoG2UgpsoF/KZvZACxBubR0= =vmrS -----END PGP SIGNATURE-----help
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