Re: ETCP Project

[Greg Lindahl <lindahl@conservativecomputer.com>]

> > It wouldn't be hard to have system calls which read execute only on
> > the local node, and system calls which write get executed on the local
> > and remote node. Voila, it's a HA component.
> 
> I don't understand.  Read what execute only on the local system?
> If it's by system call, then there's no local data to read locally.  I'm
> confused.

I didn't explain it fully.

The basic ForwardFS is forwarding system calls to another system, so
it can have any filesystem on the remote system, and there is no local
data on disk.

The HigherAvailabilityMirrorFS I described is a filesystem that can
execute a given system call in 2 places: (1) against a local
underlying filesystem (of any kind), and (2) against a remote
underlying filesystem (of any kind). PVFS is actually forwarding the
call up to a user-level process. In order to keep the 2 underlying
filesystems synchronized, you need to do all writes against both, but
reads only need to go against 1. (Screw atime.)

-- g


Linux-cluster: generic cluster infrastructure for Linux
Archive:       http://mail.nl.linux.org/linux-cluster/