On 14 okt 2008, at 18:19, Howard Coles wrote:

Really?  That's odd because from my experience I've never found tape
to
tape as fast as disk to tape.  I guess it depends on a lot of factors,
but generally speaking I've gotten better speeds going from disk,
mainly
because read times are faster from disk (especially properly
configured
local disk).

well, current tape-devices do about 120-200 MB/s, you'll really have
to push a disk to do that, so as long as you can keep your tapes
streaming....

As for disk, I might see an advantage in collocated pools, since those
will require a lot of load/unload actions from tape, but generally,
you'll find that you're doing more than one task on a single disk at
any time and keeping the disk in sequential-read or write mode is very
hard.... (seagate quotes their cheetah's as going up to 125 MB/s, a
bit less than an enterprise tape drive).

See Ya'
Howard

-----Original Message-----
From: ADSM: Dist Stor Manager [mailto:ADSM-L AT VM.MARIST DOT EDU] On Behalf
Of Allen S. Rout
Sent: Tuesday, October 14, 2008 10:50 AM
To: ADSM-L AT VM.MARIST DOT EDU
Subject: Re: [ADSM-L] Backup order

On Tue, 14 Oct 2008 10:08:54 -0500, Howard Coles

<Howard.Coles AT ARDENTHEALTH DOT COM> said:

The best I can remember you can't "migrate" into a copypool.

Right. :)

Additionally,

-----Original Message-----
From: ADSM: Dist Stor Manager [mailto:ADSM-L AT VM.MARIST DOT EDU] On

Behalf

Of Orin Rehorst
Sent: Monday, October 13, 2008 5:20 PM
To: ADSM-L AT VM.MARIST DOT EDU
Subject: [ADSM-L] Backup order

Our TSM was set up to nightly:

1. backup the VTLpool to copypool
2. backup the tapepool to copypool
3. migrate stg VTLpool (to tapepool)

Step 2 is tape-to-tape and therefore slow.

I think that you will find tape-to-tape to be as fast or faster than
disk-to-tape.

- Allen S. Rout

--

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