Switchover to CAM ATA?

Dag-Erling Smørgrav des at des.no
Tue Apr 27 14:17:03 UTC 2010

Alexander Motin <mav at FreeBSD.org> writes:
> Dag-Erling Smørgrav <des at des.no> writes:
> > Most pseudo-raid kit has nifty features like checksum offloading,
> > composite writes etc. which can improve performance considerably.  You
> > can't access those from GEOM.
> Have you ever seen them documented?

ISTR I got the info from sos@ at some point.  I have several Promise
cards lying around and was working onm RAID5 offloading, but I stopped
when ZFS became usable.

> Does the need to specifically handle dozens of incompatible
> implementations with limited resources worth those (probably not
> major) benefits?

The details probably vary from controller to controller, but the
capabilities are pretty much the same: perform the same write operation
to several disks at once, split a write operation across several disks,
compute and write parity.

IIRC, composite writes are already supported but not used.

Dag-Erling Smørgrav - des at des.no

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