[Info-vax] RAID vs. MOUNT/BIND

[Bart.Zorn@gmail.com]

On Nov 23, 9:25 pm, Ken Fairfield <ken.fairfi... at gmail.com> wrote:
> On Nov 23, 11:25 am, Rob Brown <mylastn... at gmcl.com> wrote:
>
>
>
> > On Tue, 23 Nov 2010 at 09:15 -0800, Keith Lewis wrote:
> > > ... RAID 5 should theoretically give you both performance and
> > > redundancy.
>
> > RAID 5 gives redundancy, no argument there.
>
> > RAID 5 gives good read performance, but its write performance is not
> > as good.  Each logical write becomes 4 I/O: 2 reads and 2 writes.
>
> > If all of the extra I/O is hidden in hardware with deep caches, then
> > it may not be noticeable.  Or if you don't do so many writes, you may
> > not be bothered by poor write performance.
>
> > Or at least, that is the way it seems to me.
>
> > PS:  *Is* there a host-based RAID (other than 1 and 0) for VMS?
>
> Yes, there *is* host-based raid for VMS.  In fact, I think
> that's it's product name. :-)
>
> We used it when I was at my former employer.  It's
> pretty tightly integrated, and depends upon, host
> based volume shadowing.  My recollection is that
> you have only the single choice of RAID 0+1, i.e.,
> striped shadow sets.
>
> It worked well, but could be tedious to set up
> initially.   A failed shadow set member was
> handled pretty much in the usual way, but ISTR
> the product be "happiest" if you used the RAID
> commands  to add a 3rd member to copy and
> to subsequently drop a failing member, etc.
>
> I don't recall having any failures with the product...
>
>    -Ken

There is also raid 5. And I think you can also use 5+1 but that is
probably even more tedious to set up!

Bart