[Info-vax] RAID vs. MOUNT/BIND

[H Vlems]

On Nov 17, 12:03 pm, hel... at astro.multiCLOTHESvax.de (Phillip Helbig---
undress to reply) wrote:
> I might need some logical disks bigger than any physical disks I have.  
> Controller-based RAID is not an option (don't have enough controllers
> for the needed redundancy), so the options are host-based RAID and
> volume sets.  If the only point is to create a larger logical disk,
> which is better?
>
> HELP says:
>
>      The following command creates a volume set with the logical
>      name TEST3. The volume set TEST3 is not shadowed, however each
>      element of the volume set (TEST3011 and TEST3012) is a shadowset,
>      providing redundancy for the volume set as a whole.
>
>      $ MOUNT/BIND=TEST3013 DSA3011/SHADOW=($1$DUA402:,$1$DUA403:),
>      DSA3012/SHADOW=($1$DUA404:,$1$DUA405:) TEST3011,TEST3012 TEST3013
>
> Presumably, the opposite is not possible (i.e. shadow a volume set with
> another volume set).  Right?
>
> HELP says:
>
>      If you mount an ISO 9660 volume using the /SYSTEM or /CLUSTER
>      qualifier, and the volume label is not unique within the first
>      12 characters, you must supply an alternate 12-character volume
>      label using the qualifier /BIND=volume-set-name. If you choose
>      this option, then Mount verification is disabled for the device.
>
> Why is mount verification disabled in this case? (Not relevant for my
> current problem; I just want to know.)
>
> With host-based RAID, do I have the option of a) binding several small
> shadow sets into a larger RAID 0 device or b) shadowing two (or more)
> RAID 0 devices?  If so, which is better?

Phillip,
first, I have *very* painful memories with respect to restoring bound
volumes.
We had a VAX 8550 with bind sets, three RA82 disks bound and used as
one volume.
Restoring a bindset took forever. It was more than twice as long as
restoring three
seperate RA82 disks. Modern hardware is faster but I'd hate to restore
a 3 member bindset
composed of, say, 36 GB disks.
Another thing is you ought to bind shadowsets, don't shadow bindsets.
Hans