Date: Fri, 6 Jul 2001 02:03:53 +0200 (MET DST) From: Joerg Schilling <schilling@fokus.gmd.de> To: ken@kdm.org, schilling@fokus.gmd.de Cc: freebsd-scsi@freebsd.org, gibbs@scsiguy.com, mckay@thehub.com.au Subject: Re: Problems reading burned CDs Message-ID: <200107060003.CAA04785@fokus.gmd.de>
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>From ken@panzer.kdm.org Fri Jul 6 00:45:37 2001
>>
>> >Sending a Bus Device Reset message to a target when it doesn't respond
>> >in the expected amount of time is a bug? Perhaps the driver could try
>> >an abort message first, but the behavior is not completely unreasonable.
>> >Your other complaints seem to be in regard to a "bus reset", which never
>> >occurred in this situation.
>>
>> OK, if it is no bus device reset, it should be OK.
>Eh? It is a bus device reset...
I believe you are talking about a target reset which does not reset the whole
bus but a specific target.
>> However, 5 seconds is a too short timeout.
>For what? The 5 second timeout is for a generic SCSI command facility,
>not for any particular command. 5 seconds is plenty of time for some
>commands, and way too short for others. A user savvy enough to compose
>his own CDBs should also be knowledgeable enough to specify a suitable
>timeout.
Believe that _any_ SCSI device I know will take much longer if there is some
problem to read the media.
For a hard disk you should wait at least 20 seconds for error recovery
(this means read retries _and_ eventually error correction).
If a CD-ROM uses error correction, you should give it ~ 100 seconds.
If you don't follow these rules, you will end up believing that there are
completely _unreadable_ blocks where the media is only _very hard_ to read.
Jörg
EMail:joerg@schily.isdn.cs.tu-berlin.de (home) Jörg Schilling D-13353 Berlin
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