Date: Mon, 03 Apr 2000 13:25:33 +0200 From: Sheldon Hearn <sheldonh@uunet.co.za> To: rjk191@psu.edu Cc: freebsd-questions@FreeBSD.ORG Subject: Re: ATA_STATIC_ID Message-ID: <71763.954761133@axl.ops.uunet.co.za> In-Reply-To: Your message of "Fri, 31 Mar 2000 17:15:28 EST." <20000331171528.A659@rjk191.rh.psu.edu>
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On Fri, 31 Mar 2000 17:15:28 EST, Ray Kohler wrote: > What exactly does the kernel option ATA_STATIC_ID really do? I've > seen what is said about it both in LINT and in ata(4), but I still > don't know whether it is something I should use of not. Normally, ata(4) will name disks sequentially. For example: Primary Controller ata0 | +-> Master 1GB Seagate ad0 | +-> Slave 24x CDROM acd0 Secondary Controller | +-> Master 1GB Fujitsu ad1 | +-> Slave 512MB Seagate ad2 Now, suppose that you want to put a 2GB Seagate drive in your system. You'd like the 2GB Seagate on the same controller as the 1GB Seagate because, for some reason, it just won't work on the same controller as the 1GB Fujitsu. So you decide to take out the 512MB Seagate and move the CDROM drive onto the secondary controller. Now the ata(4) driver does this: Primary Controller ata0 | +-> Master 1GB Seagate ad0 | +-> Slave 2GB Seagate ad1 Secondary Controller | +-> Master 1GB Fujitsu ad2 | +-> Slave 24x CDROM acd0 Note that the 1GB Fujitsu's drive name has changed! Some people like this behaviour, because you don't end up with ad0 and ad2 without any ad1. Some people find it annoying, because you now have to update your /etc/fstab to reflect the change. If you find this behaviour annoying, you use ATA_STATIC_ID, which causes the numbering to work as follows before the move: Primary Controller ata0 | +-> Master 1GB Seagate ad0 | +-> Slave 24x CDROM acd0 Secondary Controller | +-> Master 1GB Fujitsu ad2 | +-> Slave 512MB Seagate ad3 Note that the system reserves "ad1" for the drive that would have been plugged into the primary controller as a slave. Now, after the upgrade, you have this: Primary Controller ata0 | +-> Master 1GB Seagate ad0 | +-> Slave 2GB Seagate ad1 Secondary Controller | +-> Master 1GB Fujitsu ad2 | +-> Slave 24x CDROM acd0 Note that the 1GB Fujitsu's drive name hasn't changed. Ciao, Sheldon. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
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