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SubjectRe: IDE/ATAPI in 2.5

>From riel@imladris.surriel.com Wed Jul 17 15:37:18 2002

>> >Error handling is more than local. Some errors, you are correct, can only be
>> >handled at the SCSI layer. However, a large class of drivers (Think
>> >multi-path or software raid) want the ability to direct how SCSI handles
>> >errors themselves. It is unacceptable to have SCSI all on its own retry a
>> >medium error command x times, taking minutes before the upper layers become
>> >aware anything went wrong.
>>
>> It looks like you have the wrong ideas about software raid. If you have
>> software raid, you will stack a SW raid driver just on top of the disk
>> drivers that handle the access to the real drives. The real drives first
>> do own error handling and if they cannot correct errors, the error is
>> handled inside the raid layer.

>Did you even read what James wrote ?

>When one of the disks in a RAID array develops a bad block
>it shouldn't stall the box for minutes when the error can
>be handled by simply doing the IO from other disks instead.

Is there any problem with using a ioctl() from upper layer kernel to the low
level drivers (living under the SW raid) to reduce the number of retries to a
reasonable value in this case?

The main design goal for UNIX as to keep it simple. There is no need for a
complex cross layer error control.

Jörg

EMail:joerg@schily.isdn.cs.tu-berlin.de (home) Jörg Schilling D-13353 Berlin
js@cs.tu-berlin.de (uni) If you don't have iso-8859-1
schilling@fokus.gmd.de (work) chars I am J"org Schilling
URL: http://www.fokus.gmd.de/usr/schilling ftp://ftp.fokus.gmd.de/pub/unix
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