and if you are going for max capacity (large number of physical devices) in
order to NOT run out of slots in your processor for device controller cards,
you probably want to be looking at SSA disks ;-)

Dwight

> ----------
> From:         Roger C Cook[SMTP:rcook AT ROTECH DOT COM]
> Reply To:     ADSM: Dist Stor Manager
> Sent:         Wednesday, August 02, 2000 9:59 AM
> To:   ADSM-L AT VM.MARIST DOT EDU
> Subject:      Re: Why not use many cheap disks as a PRIMARY stg?
>
> ADSM considerations aside, from a hardware view in this environment SCSI
> is
> definitely the way to go. Not only is SCSI superior handling multiple
> simultaneous accesses, it is much less CPU intensive. When a SCSI drive is
> accessing, it normally uses 10-20% of the CPU, where IDE can use between
> 70-90%. That's why on a desktop system using IDE, when you transfer large
> amounts of data (such as copy one drive to another) the system becomes
> extremely sluggish during the transfer. SCSI will not normally have this
> impact. IDE may have evolved to surpass SCSI in some aspects, but SCSI is
> still the only choice in a server/multi-access environment.
>
> Roger C Cook
> RCG Information Services
>
>
> Hi,
>
> Recently, we're trying to decide about the various ways in which TSM can
> be
> set up. We need about 2Tb of primary pool space. For primary pool only ,
> we
> may either:
>
> 1) Get a big library, and a lot of tapes, amounts to >$50.000. (With the
> lib
> we can also maintain the copy pool)
>
> 2) Get a bunch of IDE-disk cabinets, and a lot of 70 Gb IDE disks, amounts
> to $25.000 or so (of course we will also need a small library for the copy
> pool). These cabinets have a scsi interface.
>
> It seems IDE disks are not only the cheaper, but also the much faster
> solution for daily retrieve operations. In this case we would opt for a
> RAID-5 IDE set for primary stg (but also a fast(er) SCSI system for the DB
> and LOG). With this amount of disks some are bound to crash every now and
> then, RAID-5 helps. All in all, the TSM server only 'sees' scsi.
>
> One cabinet would show up like one disk, in reality 70Gb disk times 7
> disks
> = 0.5 Tb/cabinet, which is a rather big 'disk' size.
>
> Question 1) However, on the forum no-one seems to use a PRimary IDE
> (PRIDE)
> disk pool? Why? I'm i missing something or what?
>
> Question 2) If PRIDE seems like a good solution, would the better way to
> use
> DISK devices (any TSM limits?, caused by size or sheer number of DISK
> volumes on the PRIDE disk) or FILE devices (but fragmenting files all over
> the disks, and need of reclaim)
>
> Question 3) Any (other) TSM limits endangering this plan (we are talking
> about 2Tb or more on disk...)
>
> Of course OS limits have been accounted for. It seems AIX and NT are OK.
>
> Thank you,
>
>
> Allshare Personnel BV
> Jochem van Hal
> TSM admin
> jvhal AT allshare DOT nl
>