SUMMARY: Mounting LSM disks to a non-LSM server?

From: Carlos Chua <chuacarlos_at_hotmail.com>
Date: Fri, 23 Jun 2000 23:22:23 +0123 (SGT)

Thanks to Tom for the quick reply. The answer is no, it won't work.
Below is my original question and a detailed explanation from Tom.

Best Regards,

Carlos

>From: "Dr. Tom Blinn, 603-884-0646" <tpb_at_doctor.zk3.dec.com>
>To: Carlos Chua <chuacarlos_at_hotmail.com>
>Subject: Re: Mounting LSM disks to a non-LSM server?
>Date: Fri, 23 Jun 2000 08:28:35 -0400
>
> > Hi,
> >
> > I've got a customer who wants to mount a group of disks originally from
>a
> > server (call it Server A) with LSM installed to another server (Server
>B)
> > without LSM. The customer will be using EMC Symmetrix. As Symmetrix has
>BCV,
> > which is like a hardware mirror of the data disks, this is physically
> > possible. The idea is to split the BCV from Server A and then attach
>the
> > BCV disks to Server B for database processing. However, Server B is not
> > running LSM and the customer doesn't want to install LSM on this
>machine. In
> > this case, will the data still be useful to server B? The customer is
>using
> > both AdvFS and raw device on Server A. Server B has AdvFS installed.
>Both
> > are running UNIX V4.0F.
> >
> > Thanks in advance for any help.
>
>Won't work. LSM does "interesting" things to the disks. Without LSM on
>the system you won't be able to access the disks. (There are ways that
>you can tell LSM to not do much to the disks, but there's not much point
>in doing that.)
>
>If you need to try to explain this to them, use the analogy of a backplane
>RAID controller with SCSI attached disks. Sure, you can take the disks off
>the RAID controller and move them to a system that has SCSI interfaces but
>no compatible RAID controller. They are, after all, SCSI disks. But the
>new system will almost certainly be able to make any sense of the disks or
>the data on them. They may appear to be unlabelled. If you really knew
>enough about the way the RAID controller worked, you might be able to write
>software that would read the raw disks (no file system interface) and then
>export a software "pseudo-disk" that would look like what the RAID hardware
>was doing.. But then you'd have invented LSM.
>
>Some backplane RAID controllers do offer a "just a bunch of disks" style of
>interface, in which they don't do any RAID functions, but just operate as
>a simple SCSI interface controller. In that mode, you MIGHT be able to
>move the disks to a simple SCSI controller and access them, but you might
>find the RAID controller had done something on the disks that differs from
>what UNIX would do on a simple SCSI controller attached disk, and that
>might keep it from working. (I don't know just how hard it it to get LSM
>to manage the disks with NOTHING special done; after all, why would anyone
>bother?)
>
>Tom
>
> Dr. Thomas P. Blinn + UNIX Software Group + Compaq Computer Corporation
> 110 Spit Brook Road, MS ZKO3-2/W17 Nashua, New Hampshire 03062-2698
> Technology Partnership Engineering Phone: (603) 884-0646
> Internet: tpb_at_zk3.dec.com Compaq's Easynet: alpha::tpb
> ACM Member: tpblinn_at_acm.org PC_at_Home: tom_at_felines.mv.net
>
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>
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>
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> -- Phil Agre, pagre_at_alpha.oac.ucla.edu
>
> Yesterday it worked / Today it is not working / UNIX is like that
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>
> Opinions expressed herein are my own, and do not necessarily represent
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>

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Received on Fri Jun 23 2000 - 15:23:44 NZST

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