On 9x, when SCSI miniport “tells” port to limit maximum transfer size, the port driver for large data transfers chunks the overall IO requests into series of 4Kb requests. That would work fine for most disk drives (the performance would suck, but it would work)…
Does anyone knows what would happen if the sector size of the particular hard disk is more than 4Kb (this could be a custom OEM audio-video disk drive)?
Typically, it will return the first 4Kb of the sector and indicate an
insufficient buffer size. I’m not sure what Win9x would make of this sense
data. The next read would read the next sector, so would skip data not
originally returned by the first sector read. NT faces the same problem
when using tapes that have say 1MB block sizes. Since SCSIPORT chunks it
up, it actually just reads the first x KB of each block until it returns 1MB
of useless data. I think there is a SCSI command that allows you to read
the device’s memory buffer directly, but this would require bypassing
SCSIPORT directly by using SCSI passthru (I’m assuming that Win9x supports
SPTI here). This might even require vendor-specific commands to achieve,
and you’re much more likely to encounter firmware
bugs/incompatibilities/limitations preventing you from implementing what you
want. This path is fraught with danger, but you might be able to get it to
work.
Regards,
Paul Bunn, UltraBac Software, 425-644-6000
Microsoft MVP - Windows NT/2000/XP
http://www.ultrabac.com
-----Original Message-----
From: xxxxx@KrollOntrack.com [mailto:xxxxx@KrollOntrack.com]
Sent: Monday, February 24, 2003 10:37 AM
To: NT Developers Interest List
Subject: [ntdev] Odd disk sector sizes and scsi miniports on 9x???
On 9x, when SCSI miniport “tells” port to limit maximum transfer size, the
port driver for large data transfers chunks the overall IO requests into
series of 4Kb requests. That would work fine for most disk drives (the
performance would suck, but it would work)…
Does anyone knows what would happen if the sector size of the particular
hard disk is more than 4Kb (this could be a custom OEM audio-video disk
drive)?
wrote in message news:xxxxx@ntdev…
>
> On 9x, when SCSI miniport “tells” port to limit maximum transfer size,
the port driver for large data transfers chunks the overall IO requests into
series of 4Kb requests. That would work fine for most disk drives (the
performance would suck, but it would work)…
> Does anyone knows what would happen if the sector size of the particular
hard disk is more than 4Kb (this could be a custom OEM audio-video disk
drive)?
That’s somewhat dependent on how the miniport and SCSIPORT interpret the
INQUIRY (or Identify) data from the device, and respond to the parameters
that differ from the expected norms.
Theoretically, you could write a SCSI miniport and SCSIPORT that aren’t
dependent on a 512 byte sector size. You’ll have to ask MS (and possibly
the HBA vendor) how well they’ve accomplished that.
You’ll probably need to ask what the expected behavior is when the device
reports a sector size larger than the maximum transfer size of the
HBA/Miniport. If the Port/Miniport/HBA can’t handle your sector size,
hopefully it would simply refuse to do anything with the device, instead of
damaging data.
Phil
–
Philip D. Barila
Seagate Technology, LLC
(720) 684-1842
As if I need to say it: Not speaking for Seagate.
There is a great thread on the t13 mailing list that occurred in the
last month that discusses this exact issue in great detail. Search for
the archives to the list.
Jamey
-----Original Message-----
From: xxxxx@lists.osr.com
[mailto:xxxxx@lists.osr.com] On Behalf Of
xxxxx@KrollOntrack.com
Sent: Monday, February 24, 2003 10:37 AM
To: NT Developers Interest List
Subject: [ntdev] Odd disk sector sizes and scsi miniports on 9x???
On 9x, when SCSI miniport “tells” port to limit maximum transfer size,
the port driver for large data transfers chunks the overall IO requests
into series of 4Kb requests. That would work fine for most disk drives
(the performance would suck, but it would work)…
Does anyone knows what would happen if the sector size of the particular
hard disk is more than 4Kb (this could be a custom OEM audio-video disk
drive)?
You are currently subscribed to ntdev as: xxxxx@storagecraft.com
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“Jamey Kirby” wrote in message news:xxxxx@ntdev…
>
> There is a great thread on the t13 mailing list that occurred in the
> last month that discusses this exact issue in great detail. Search for
> the archives to the list.
>
> Jamey
A few weeks ago, someone mentioned t10 or t13 didn’t archive the reflector,
though I can’t find that message, maybe it was on one of the ms.public
newsgroups. Anyway, maybe t13 doesn’t, but someone does… (Google saves
the day again!)
http://www.mail-archive.com/forum@t13.org/index.html
Phil
–
Philip D. Barila
Seagate Technology, LLC
(720) 684-1842
As if I need to say it: Not speaking for Seagate.