[Cluster-devel] GFS + iscsi target + LVM performance and file integrity

[अनुज Anuj Singh]

Hi,
Thanks for the reply.
I found this page, talking about simultaneous read/write to a single file
system.

http://www.redhat.com/gfs/
snap--------------------
Red Hat GFS is commonly used in clusters of enterprise applications to
provide high speed access to a consistent file system image across the
server nodes. This allows the cluster nodes to simultaneously read and write
to a single shared filesystem. Typical application clusters where Red Hat
GFS is deployed today include:
-------------------------end of snap


Please can I have some technical idea, doc or flow chart type of thing
regarding GFS mechanism.
Thanks and Regards
Anuj Singh.

On Wed, Apr 30, 2008 at 1:00 PM, Christine Caulfield <ccaulfie at redhat.com>
wrote:

> ???? Anuj Singh wrote:
> > Hi,
> > I have a question related to GFS + LVM and iscsi.
> > 1). I have a file test.txt on shared GFS file system, some user ramesh
> > opens test.txt to read, at the same time some other user Smith on the
> > network writes some data to test.txt file.
> > What data will Ramesh see in test.txt file which is changed after he
> > opened?
> > How does GFS handles data integrity?
>
> The same thing happens on GFS as would occur if you did that on a local
> file system. GFS does not provide any additional data integrity features
> over other file systems. If you can corrupt a file by writing to it from
> two places using ext3 on one node, then the same thing will happen using
> GFS, regardless of whether the processes are on the same or different
> nodes.
>
> The point of GFS is not to provide data integrity, but /metadata/
> integerity. ie, the filesystem itself does not become corrupted by two
> nodes writing to the same inode or directory.
>
> So, the basic rule is: if it would corrupt data if two people on the
> same node did it on next3, then it will also corrupt data if two people
> on different nodes did it on GFS.
>
> I hope that's clear!
> --
>
> Chrissie
>
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