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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--VbJkn9YxBvnuCH5J Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Hello, After my dump/restore test failed back in May of 2010[1], I finally got=20 around to burning a test DVD after installing about 2.5 inches of=20 semi-rigid foam under the machine to dampen any local vibration. In designing the test, I was under the mistaken impression that buffer=20 under-runs would reduce the amount of space for writing. Apparently,=20 DVD+R media supports loss-less linking[2]. Test Procedure (using ATAPI interface, rather than the newer ATAPI/CAM=20 interface). The man pages do not imply any major differences for this=20 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=3Daux45G count=3D2197266 bs=3D2048 | md5 3. Write test disk: # dd if=3D/dev/urandom bs=3D2048 count=3D2295104 | \ tee auxout aux45G | dd of=3D/dev/acd0 bs=3D2048 Error: dd:/dev/acd0: Input/output error 679+0 records in 678+0 records out 1388544 bytes transferred in 80.97 seconds=20 (step 4 not completed due to premature burn failure after 684=20 blocks, 80 seconds (from 'dd if=3Daux45G'...) (15743 bytes/sec)) Drive spun up at least twice during this time. 4. Read test (in another term 'cat aux45G | md5') # dd if=3D/dev/acd0 bs=3D2048 count=3D2295104 | tee aux45G | md5 Questions: Currently, the drive is locked. Before forcefully ejecting it and=20 risking an new disk, I want to know what may have gone wrong. Was=20 I expecting too much of FreeBSD on old hardware?=20 The hardware is a Pentium-II desktop machine with 256MB of RAM, with a=20 Promise ATA100 controller card. An extra-long 80-wire cable is in use=20 (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=3D/dev/urandom of=3D/home/test Wrote at 4485315 bytes/second: faster than I was expecting (based on=20 linux's slow urandom function), but still slow enough to cause buffer=20 under-runs. So the second question is: do I have to do anything special=20 to enable buffer underrun protection? (with DVD+R's lossless linking=20 feature, no data should be lost.) How important is running ATAPI/CAM? Obviously DVD burning was happening=20 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=20 bug that only shows up on old hardware or heavy load? (Or possibly drive=20 firmware bug?) Regards, James Phillips # uname -a FreeBSD dusty.inet 8.0-RELEASE FreeBSD 8.0-RELEASE #0: Sat Nov 21=20 15:48:17 UTC 2009 =20 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=3D290415+0+archive/2010/freebs= d-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? --=20 OpenPGP Public Key: http://phillipsjk.ca/signature0611.txt --VbJkn9YxBvnuCH5J Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.6 (GNU/Linux) iD8DBQFOq90FPPYMXhz9onsRAoymAJ4mf2X8f1Z88150dkoNuU1w5RpfkgCdHiih FoG2UgpsoF/KZvZACxBubR0= =vmrS -----END PGP SIGNATURE----- --VbJkn9YxBvnuCH5J--
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