Stuart D. Gathman wrote:
How does SATA fit in with all of this? Is it basically the same
limitations on the bus as IDE/PATA, so that you'd really not want to put
more than 1 device per bus?
SATA mandates at most 1 disk per channel, making the issue moot. It is
still true that there is only one active disk on a bus. But then there
is only one disk on a bus.
Newer SATA drives, with proper newer controllers and proper device
driver support will support NCQ (native command queueing), which
allows the drive to re-order requests. It appears that the Linux ACHI
and Nvidia SATA drivers support this capability in recent kernels.
Of course, any of the re-ordering (SCSI TCQ, or SATA NCQ) requires
filesystem and driver support of write barriers for reliability.
Write barriers are not implement in DM, hence LVM, so there is a
reliability risk in going with this kind of solution. Depending on
the filesystem this can result in power failures resulting in files
having inconsistent data.