[Linux-cluster] iscsi doubt

[ESGLinux]

Thank you ALL


Finally the light came to me,

I thought that iscsi was a file sharing protocol and now I see  it isn´t.

I think I´m going to implement GFS on it, (its a good oportunity to learn
something new :-)

Thaks all again for your help

ESG


2009/4/20 Graham Wood <gwood at dragonhold.org>

> On Mon, Apr 20, 2009 at 06:56:23PM +0200, ESGLinux wrote:
> > Yes I agree with you, but I thought with iscsi i can do the same as with
> > NFS.
> No. iSCSI is a way of remotely getting access to a block device.  NFS is a
> way of accessing
> a network filesystem.  They server completely different purposes, and run
> at different parts
> of the "stack" as well.
>
> > any suggestion that makes me see the light ;.)
> As has already been stated, you cannot do it.
>
> You cannot mount ext3 on two machines at the same time, and write data.  If
> you want to
> write from one at a time, don't mount it on the other.  It's THAT simple.
>
> There is NO other answer with ext3.  If you want to have it mounted twice
> your choices are:
> - NFS
> - GFS/OCFS2/etc.
>
> The standard reason for wanting to avoid GFS and the like is the complexity
> - unfortunately
> the complexity is required because (as previously stated) of cache
> coherency.
>
> As for your example of NFS, I can tell you from experience that it doesn't
> work as well as
> you seem to think - it is still quite possible for NFS to get things wrong,
> and give you the
> wrong data - however, the protocol has been designed with that in mind, and
> you get
> "sensible" errors when it detects things.
>
> We've got NFS servers that are accessed by 1000+ clients - and creating a
> file on one can
> take a few minutes to appear on the others, however the way NFS works means
> that this is
> done "safely", and it will recover.  Ext3 has NO functionality to do this.
>
>
> So, in summary, "No".
>
> Graham
>
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