Joshua,

> > I never understood why some users wanted their disk storage pools
> > mirrored when tape wasn't.
>
> Ah, but tape can be "mirrored" as long as you create multiple copies of
> the data on the first tape.
>

        as you said you can "mirror" a tape simply backing up the content of the
Primary Tape Pool to a Copy Pool, but in the same way you can backing up the
content of a Primary Disk Pool to a Copy Pool ... sorry but I can't see any
difference!

Although I agree with you that a disk-mirror gives you immediate protection.

I don't mirror my diskpool, I simply back them up twice a day, I consider them a
cache that allow me to spawn multiple backup sessions.

Mauro, STM

> The best example I can give of an instance where you would want to mirror
> your stg volumes would be when you are using either HSM or archiving the
> data and then deleting the original files.  Then you are guaranteed that
> if one of your disk vols is lost you would still have the data on a
> second.
>
> Then to avoid the single point of failure of the tape when you perform
> migration would be to backup your disk pool to your primary tape pool
> and then again backup your disk pool to your tape copy pool.
>
>
> Joshua S. Bassi
> Storage Management Team Lead
> Tivoli Certified Consultant - ADSM V3
> IBM Certified Specialist - AIX and
> Mid-Range Storage Technical Solutions
> Dickens Services Group
> (404) 386-9848
> jbassi AT gloryworks DOT com
> www.TeamDSG.com
>
> -----Original Message-----
> From: ADSM: Dist Stor Manager [mailto:ADSM-L AT VM.MARIST DOT EDU]On Behalf Of
> Alan R. White
> Sent: Wednesday, August 25, 1999 12:58 PM
> To: ADSM-L AT VM.MARIST DOT EDU
> Subject: Re: Comments solicited about a disk pool plan?
>
>
> Allen
>
> Looks good to me - database inJFS mirrored by ADSM, multiple ADSM volumes in
> raw LVs in each disk storage pool - someone somewhere once said ADSM can
> only have one write outstanding to any volume so split large (disk stg)
> volumes into multiple smaller ones for high concurrent workloads. If anyone
> knows different I'd like to hear.
>
> On the availability side do you have the disks used for database and logs
> available through different SSA adapters? AIX level mirroring of disk stgs
> hampered write performance severely last time I tried it so that seems to be
> a no-no - I never understood why some users wanted their disk storage pools
> mirrored when tape wasn't.
>
> My #0.02 (UKP)
>
> Regards
> Alan