From owner-freebsd-scsi  Mon Apr 24  8:15: 5 2000
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Subject: Safe mounting of one file system on multiple hosts?
From: sthaug@nethelp.no
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Date: Mon, 24 Apr 2000 17:15:00 +0200
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I have a RAID system from Nexsan (www.nexsan.com), which is basically
two CMD CDR-5644 controllers in a hot-standby configuration. The system
has two host channels, and two disk channels. I have two different hosts
connected to the two hosts channels.

Normally, I would configure two (or more) RAID sets, and have each RAID
set dedicated to one host (visible on only one of the host channels).
Each RAID set appears to the host as one disk - and can be partitioned,
newfs'ed etc. with normal FreeBSD tools. This works fine.

However, I also have the *option* of making all RAID sets visible on
*both* host channels. I don't want to try read/write mounting one RAID
set on two hosts - but can I safely read/write mount the RAID set (its
corresponding file system(s)) on one host, and mount it readonly on the
other host? I guess the basic question is: Will a readonly mount of a
file system lead to *zero* writes to this file system?

Steinar Haug, Nethelp consulting, sthaug@nethelp.no


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