Another advantage of cache is to increase the number of concurrent client
sessions.  Going direct to tape limits the number of concurrent sessions to
the number of tape drives available, minus drives needed for ADSM
maintenance processes (space reclamation most notable -- takes 2 drives).

Best regards,
Ray Kampa
MCI / WorldCom

> -----Original Message-----
> From: Richard Sims [SMTP:rbs AT BU DOT EDU]
> Sent: Friday, December 18, 1998 11:42 AM
> To:   ADSM-L AT VM.MARIST DOT EDU
> Subject:      Re: %Util vs %Migr
>
> Betsy - One would not use caching if the recall pattern did not make
>         its use worthwhile, to eliminate some overhead.  In most
> shops, an initial disk in a backup storage pool hierarchy basically
> serves as a buffer rather than a repository: it's usually "write-only"
> with minimal prospect of retrieval.  In such situations this just
> presents ADSM with more work to do in maintaining the cache, including
> rapidly having to dismiss cache images when more space is called for.
> Caching makes a lot more sense for Archive and HSM storage pool disk,
> where recall of files is more probable.
>    Richard Sims, BU