Bartlomiej Zolnierkiewicz wrote:
On Tuesday 14 April 2009 12:14:00 Jeff Garzik wrote:
The SATA features that needed SCSI infrastructure came 2 years later.
Moving libata out of SCSI is now a long term, far off goal. A goal that
implies many intermediate steps, cleanups to block, libata, IDE, SCSI
and other block drivers.
"far off"?
The fact that it is much harder to do nowadays than in 2004-2005 (without
ATAPI support, PATA support and heavy dependence on SCSI infrastructure)
is only _your_ fault.
Of course it is. Use of SCSI driver infrastructure was a sound
technical decision, I'll happily defend. Key reasons SCSI core was used:
* ATA-SCSI convergence was clear when libata began. Time has proven
this true:
ATAPI was always SCSI-like. SAS is plug-compatible with SATA [for some
SAS plugs], and SAS transmits SATA frames from SAS expanders and SATA
port multipliers. T10 and T13 standards committees actively
collaborate. SCSI even has a specification, SAT, that describes how to
best co-mingle ATA with SCSI.
* SCSI driver infrastructure was the only one advanced enough to support
controller hotplug, device hotplug, and all sorts of queueing contortions.
* SCSI was the only infrastructure that _guaranteed_ it would work with
existing installers and distros. For users, there is a clear level of
difference in support between /dev/hdXX, /dev/sdXX, and every other
block device in the kernel.
SCSI had a higher Just Works(tm) value at the time.
Jeff
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