[PC-BSD Testing] Support for J-Micron?

Jeff dejamuse at yahoo.com
Wed Dec 2 05:05:35 PST 2009

The RAID array is managed by an onboard ROM based controller, Intel matrix.

I previously had my system setup as RAID - 0 but it failed after a few months. Assuming a drive had failed I replaced both and the array broke again.  Gave up on RAID - 0.

Guess I'll have to give up on eSATA for now and just use the USB connection.


--- On Wed, 12/2/09, Josh Paetzel <josh at tcbug.org> wrote:

From: Josh Paetzel <josh at tcbug.org>
Subject: Re: [PC-BSD Testing] Support for J-Micron?
To: "PC-BSD Testing list" <testing at lists.pcbsd.org>
Cc: "PC-BSD Testing list" <testing at lists.pcbsd.org>
Date: Wednesday, December 2, 2009, 7:21 AM

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 booted. 
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. 
Josh Paetzel
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