Yes, it is possible to have VTS without real tapes on backend. Some
vendors do offer only "tapeless tapes", with no option to connect real
tape library.
However from OS point of view there is difference between disk (DASD)
and tape (offline storage).
Price difference is also worth to consider, however I mean the logic.
Even the biggest, cheapest and really huge DASD will not protect you
form human and application (and other) errors. But backup will do it.
That's why we do backups. We don't afraid of disk failure, because we
have RAID, spare modules and possibly remote copy. However we do backups.
If you insist on DASD, you may (theoretically) connect another DASD box
dedicated for backups only. And even (logically) disconnect it between
backup sessions. However it is IMHO worse version of VTS.
Note: I do not discuss here things like price (initial, per terabyte),
compression, thruput, scalability, RAID, etc.
--
Radoslaw Skorupka
Lodz, Poland
W dniu 06.07.2020 o 16:46, kekronbekron pisze:
Hmm... do a lot of shops use actual cart based tapes ... TS77xx with TS4x00?
Don't know if EMC DLm has a cart back-end option.
If it's VTL with disk back-end, is that any different from having it all on
DASD?
- KB
‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐
On Monday, July 6, 2020 4:25 PM, R.S. <r.skoru...@bremultibank.com.pl> wrote:
I forgot something obvious for me: NEVER USE TAPES FOR APPLICATION DATA.
No jobs should write or read tapes.
Nothing except backup and restore and (optionally) ML2. Managed by HSM
or FDR. Some excepions for archive copies are worth to consider.
Note: you may have 15 years old backup on new shining tape. Migration
from older tape is no nightmare at all. It is simple.
---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Radoslaw Skorupka
Lodz, Poland
W dniu 06.07.2020 o 12:49, R.S. pisze:
W dniu 05.07.2020 o 14:12, kekronbekron pisze:
Hello List,
Just wondering ... assuming there's a primary storage product out
there that can store how-many-ever hoo-haa-bytes, and is a good
product in general, it should make sense to begin eliminating all
tape (3490/3590) use right?
First, ML1 & ML2 in HSM, then HSM itself, then rebuild jobs to write
to disk, or do SMS/ACS updates to make it all disk reads/writes.
Looking at the current storage solutions out there, this is possible,
right?
What would be the drawbacks (assume that primary storage is super
cost-efficient, so there's no need to archive anything).
Few remarks:
Even the cheapest possible DASD will not replace backup and other
things (archive copy, etc.)
I did replace 3490E tapes with really cheap second hand DASD boxes, it
was approx. 20 years ago. Been There, done that. It wasn't very fine
solution, it was cheap and working. AFAIR HSM does not like DASD as
the output for some activities, can't remember details.
Someone wrote about tapes moved to DR shelter. That's very
old-fashioned. I would strongly prefer to have remote copy, that means
two dasd-boxes and connectivity between.
There are products for tape emulation on CKD disk. It is definitely no
cheap. It also consume MSU.
Tapes, even virtual tapes are OFFLINE media from MVS point of view.
Offline media are good for some oooops! mistakes.
Last, but not least: you assumption is far from reality. DASD is still
more expensive than tape. The more capacity the difference is bigger.
Tape (real one) is cheap when talking about carts and very well
scalable. However tape realm with "first cart" is extremely expensive,
because drives are expensive, controllers are expensive and ATLs are
expensive.
The real decision depends strongly on your capacity, your predicted
growths, your needs and budget.
==
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