On 3/28/2013 8:27 AM, Scott Long wrote:
On Mar 27, 2013, at 4:13 PM, Matthew Jacob <mja...@freebsd.org> wrote:
On 3/27/2013 2:22 PM, Alexander Motin wrote:
Hi.
Since FreeBSD 9.0 we are successfully running on the new CAM-based ATA stack,
using only some controller drivers of old ata(4) by having `options ATA_CAM`
enabled in all kernels by default. I have a wish to drop non-ATA_CAM ata(4)
code, unused since that time from the head branch to allow further ATA code
cleanup.
Does any one here still uses legacy ATA stack (kernel explicitly built without
`options ATA_CAM`) for some reason, for example as workaround for some
regression? Does anybody have good ideas why we should not drop it now?
Some people have expressed performance concerns about ATA_CAM. I have not
validated those concerns. Does anyone know of any?
The albatross of "CAM is slow" comes up over and over, but I never see any data
to support the claims. So here's an anecdote of my own.
Yes, I understand that. Like I said, they didn't give me details about
it, but it did seem like some data they were throwing around showed a
falloff that was significant. However, they have a number of other
differences which, for whatever reason, may not have played well. I'm
waiting for more info on it.
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