I did NOT say "replicated copy".
Backup on DASD means some form of *backup*, but on DASD.
"Replicated copy" - I understand it as remote copy, like PPRC, SRDF,
TrueCopy, etc. - it is NOT a backup. Such copy protect my data against
datacenter disaster, but not against software or human error. That's
obvious.
"air gap" could mean it cannot be destroyed by the human or software
error, just by mistake. It can be really air gap - like cart on desk (or
better in some safe). Less secured (against human) is copy in the ATL or
VTS or on DASD. However every of the three provide *the same* in my
opinion level of "air gap".
I'm sorry, but the only reasons for using VTS with no real tapes at
backend are:
1. VTS disk storage is cheaper than MF DASD.
2. Backup software cannot use disks as a media, it demands tape-like
devices. Even emulated.
Regards
--
Radoslaw Skorupka
Lodz, Poland
W dniu 2018-12-07 o 14:29, Russell Witt pisze:
Where I disagree is when you compare a "backup with air gap" to a "replicated copy". A replicated copy is corrupted at
the same time that primary is corrupted. A "backup with air gap" is not. Now, can you create a "backup with air gap" on
DASD - yes, I believe you can now. However, a "backup on DASD with air gap" means having the backup on expensive MF-DASD while
"backup on virtual-tape" implies both the air-gap and usage of cheaper DASD. Plus, replicated virtual-tape means the air-gap
backup is both a local copy and a remote copy.
Sorry, but for backups I still believe that tape is the superior solution. Now,
granted the new HSM-archive to the cloud is wonderful and will further decrease
the usage of tape in most data centers; but many of the production sites I have
reviewed show that HSM-archive data is only about 25% of their overall tape
usage. Still, a large chunk - no question.
Russell
-----Original Message-----
From: IBM Mainframe Discussion List [mailto:IBM-MAIN@LISTSERV.UA.EDU] On Behalf
Of R.S.
Sent: Friday, December 7, 2018 2:58 AM
To: IBM-MAIN@LISTSERV.UA.EDU
Subject: Re: Another IBM tape not for z/OS
IMHO, the air gap for tape in ATL or even more for virtual tape is as
(in)secure as copy on DASD.
Disclaimer: I understand "air gap" as "physical separation" backup from the
system, just to be sure the backup cannot be destroyed by human mistake or any other error. I hope
I understood this idiom correctly.
--
Radoslaw Skorupka
Lodz, Poland
W dniu 2018-12-05 o 14:39, Russell Witt pisze:
So very true. And the concept of an "air-gap" backup has become a real issue and shows
one of the problems with replication. And nothing is better for an "air-gap" backup than
tape, including Virtual Tape.
The other point is that while dasd-management products (HSM, FDR/ABR, CA-Disk)
are one of the biggest users, and together with backup-solutions like DFDSS and
FDR account for the majority of tape usage there are other uses as well. I have
seen some production sites where DB2 backups from the DB2 utility use as much
tape (measured in Mb of data) as either one.
Russell Witt
-----Original Message-----
From: IBM Mainframe Discussion List [mailto:IBM-MAIN@LISTSERV.UA.EDU] On Behalf
Of Joel C. Ewing
Sent: Tuesday, December 4, 2018 9:30 AM
To: IBM-MAIN@LISTSERV.UA.EDU
Subject: Re: Another IBM tape not for z/OS
On 12/02/2018 07:55 PM, Rugen, Len wrote:
Batch tape should be dead, even if batch JCL still looks like tape is used.
One of my last SMS projects was to manage tape, redirecting almost all to SMS
disk.
Before employing any technique to convert all tape data sets to DASD, one
should I hope first consider whether replacing a tape data set with a DASD data
set is a reasonable act based on the application design. The one logical
capability of a tape data set, even one using virtual tape, that is not
normally associated with a DASD data set is the innate ability to continue to
exist for hours, days, or even longer after a new data set with identical name
has been created, depending on how tapes volumes are scratched. The use of
tape could mean the application is depending on that retention as an implicit
and essential part of recovery should programming errors or other disasters
occur during application processing, especially if the problem is a subtle one
that isn't caught immediately. Throwing out that capability without providing
a suitable substitute is something you may live to regret.
Joel C. Ewing
--
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