Weird, man.
Why not re-arrange it like this:
_____________
| |
| NAS storage |
|_____________|
|
| ethernet
__|__
| |
| hub |
|_____|
||___________
| |
|ethernet | ethernet
________|_ _|________
| | | |
| Server A | | Server B |
|__________| |__________|
NASs (look in the Harris Tech catalogue) http://www.ht.com.au
might not be as fast as direct SCSI connection but they do allow NFS
connections
and, well, NFS is a bit like magic. Both machines would be able to "see" the
mounted partition provided it was mounted as NFS.
Warning: some of the NASs run Windoze; avoid if you are using it with an
all-Linux system as you are only paying for a license you don't need
(blablabla).
Cheers,
Jill.
--
Jill Rowling, Snr Des. Eng. & Unix System Administrator
Eng. Systems Dept, Aristocrat Technologies Australia
Level 2, 55 Mentmore Ave Rosebery NSW 2018
Phone: (02) 9697-4484 Fax: (02) 9663-1412 Email: [EMAIL PROTECTED]
-----Original Message-----
From: Wienand Ian [mailto:[EMAIL PROTECTED]]
Sent: Thursday, 18 April 2002 11:07
To: 'Grant Parnell'
Cc: [EMAIL PROTECTED]
Subject: RE: [SLUG] Sync of filesystem on multiple SCSI hosts
firstly what file system are you using? i can't see this working with any
standard non distributed file system.
i've never seen anything like this -- two pc's essentially using a single
disk. but everything makes me think that this would not be a good solution
as i can't think of any file system that was developed to be used like this.
the problem is one of abstraction; the scsi bus handles putting blocks onto
the disk, and that is all. the os filesystem functions organise those
blocks into an entity that is file system. a user space protocol and
daemons such as NFS can handle multiple accesses and sort them out for
handing down the chain.
i can't see how this setup can guarantee normal unix semantics ; i.e. a read
after write returns the value just written and two writes returns the latest
write. if this fails, then so does everything built ontop of it. why you
can't see updates i don't know, but i think that would only be a symptom of
a larger problem.
for what it's worth, i can't see this working without some sort of
distributed file system, e.g. nfs or samba. failing that, you would have to
write your own file system that implements some sort of session semantics,
immutable files or atomic transactions or some other scheme you think of
yourself. sounds like fun but probably not the easiest way to solve the
problem.
i'm happy to be corrected on any of the above points, however.
-i
> -----Original Message-----
> From: Grant Parnell [SMTP:[EMAIL PROTECTED]]
> Sent: Thursday, April 18, 2002 10:40 AM
> To: [EMAIL PROTECTED]
> Subject: [SLUG] Sync of filesystem on multiple SCSI hosts
>
> I have a client with the following setup:
>
> __________________
> | |
> | Firewire storage |
> |__________________|
> | |
> | |
> ________|_ _|________
> | | | |
> | Server A | | Server B |
> |__________| |__________|
>
> This is not an NFS mount, the box has multiple SCSI buses.
>
> Both Server A and Server B mount the same filesystem and my client says
> that when files are written by Server A the only way they can be seen on
> Server B is to unmount the filesystem and re-mount it. I did suggest using
> the sync option when mounting the filesystems and also trying the sync
> command but this didn't help.
>
> Effectively we need to lose the linux filesystem buffers (and yes, all the
> efficiency that goes with that) I think but I don't know how to do that.
>
> Possibly this could be done periodically on each server to allow some
> level of filesystem efficiency but I'm guessing this would be more
> trouble.
>
> If this isn't easy I'm going to have to suggest NFS... wonder if you can
> do NFS over SCSI? I've heard of TCP/IP over SCSI I think. I do not know if
> the Servers can see each other on the SCSI buses, certainly not visible in
> /proc/scsi areas so my guess is no.
>
> --
> ---<GRiP>---
> Grant Parnell - senior consultant
> For all your Linux Commercial quality support and consulting needs
> Web: http://www.linuxhelp.com.au Email: [EMAIL PROTECTED]
> For retail sales see http://www.everythinglinux.com.au
> Phone 02 8753 0792 to book service.
>
> --
> SLUG - Sydney Linux User Group Mailing List - http://slug.org.au/
> More Info: http://lists.slug.org.au/listinfo/slug
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