Date: Sat, 16 Jan 1999 02:20:06 -0800 (PST) From: asami@cs.berkeley.edu (Satoshi Asami) To: current@FreeBSD.ORG Subject: mounting double-ended SCSI disks Message-ID: <199901161020.CAA47520@silvia.hip.berkeley.edu>
next in thread | raw e-mail | index | archive | help
Hi, In our project, we're trying to connect two PCs to both ends of a SCSI chain. I've got it somewhat working, but have a couple of questions re. mounting the filesystems. If I mount the filesystem from one machine (A) as read-write, then the other one (B) can't mount it read-write because the clean flag is not set. This is ok. Also, I can mount the disk read-only from both A and B. (I even read the entire contents of a 20GB partition from both machines at the same time -- worked without a hitch.) However, if I try to mount it from B read-only while A is mounting it read-write, it succeeds. This looks dangerous, as A writing data onto the disk could cause B's cache to go stale without B knowing it. Is it a good idea to allow read-only mounts of a dirty filesystem anyway? (The filesystem could be corrupted, right?) Another problem is if A is mounting it read-only and then B tries to mount it read-write. This succeeds and is dangerous for the same reason as the last example. Since A can't write anything to the disk, I guess there is no way we can avoid this situation. (The only way I could think of avoiding a crash due to stale cache data was to have A check the clean flag before every read, but that seems excessively expensive.) Satoshi To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?199901161020.CAA47520>