[PC-BSD Testing] Support for J-Micron?
josh at tcbug.org
Wed Dec 2 04:21:51 PST 2009
On Dec 2, 2009, at 1:09 AM, Jeff <dejamuse at yahoo.com> wrote:
> I tried that at first but ad0 and ad1 are the two main drives and
> I'd assume they'd be the same since it's a RAID-1, mirrored.
> Mounting either of those drives shows the contents of the system.
Couple of things:
The last eSATA controller I had didn't support hot plugging in
FreeBSD. A drive attached when the system booted would be seen, but
the system would not recognize drives attached after the system was
PATA supports two devices per controller, generally refered to as a
master and a slave. The controller cannot access both devices
simultaniously. In a perfect world the devices in your mirror would be
on seperate controllers. I don't know how smart the ar driver is about
reads, but theoretically having the drives on seperate controllers
would allow for two concurrent reads simultaniously. It could also
allow for better resiliancy in the case of an unclean shutdown. In
your current setup, writes are always serialized. If the system were
to crash during a write the mirror would almost certainly need to be
resynced. Anyways, you might contemplate moving the drive that is the
primary slave (ad1) to being on the other IDE controller. It may or
may not have some tangible benefits, in theory it should.
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