Date: Mon, 28 Apr 2003 08:41:10 -0700 (PDT) From: Matthew Dillon <dillon@apollo.backplane.com> To: Geoffroy Desvernay <dgeo@esm2.imt-mrs.fr> Cc: freebsd-stable@freebsd.org Subject: Re: sharing scsi disk beetween two freesbd's ... Message-ID: <200304281541.h3SFfARi045685@apollo.backplane.com> References: <3EAD48E8.2020401@esm2.imt-mrs.fr>
next in thread | previous in thread | raw e-mail | index | archive | help
:This is a cryptographically signed message in MIME format.
:
:--------------ms000201080102020100060303
:Content-Type: text/plain; charset=ISO-8859-15; format=flowed
:Content-Transfer-Encoding: 7bit
:
:I want to use one scsi disk with two redondant servers, mounted r/w on server A and r/o on
:server B.
:Everything works, except that when I write data from server A, I can't read it on server B
:before un-mounting the disk ant re-mounting it... (with AND without soft-updates)
:
:Is there any way to mount a disk r/o keeping in sync with real disk data ?
:
:Thank you.
:
:--
:Geoffroy DESVERNAY
The machines cache the disk data in memory, so if one machine has read
a track and the second machine writes it, the first machine will not see
the changes until it flushes its caches (which may be never).
Also, what you are doing is extremely dangerous. Even the machine with
the read-only mount is going to assume that the data on the disk is not
going to change out from under it, and when it does you could crash the
kernel.
A better solution would be to attach the disk to a single machine and then
export the filesystem to the second machine via NFS.
-Matt
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?200304281541.h3SFfARi045685>