Re: [Networker] Query in Staging from adv

The implementations I've done, cloning outside the VTL was the right way to
do it.

Cloning in NW is not that hard, it does take some effort, but when you're
cloning from VTL to physical tape autoclone works pretty good and is very
easy to configure. I haven't seen any performance hit from doing that.

Volume sizes are purposely kept smaller or not filled up in the VTL as a
best practice. Thin provisioning and all. Physical tape is what it is.
NetWorker manages that difference better by filling up physical tapes
completely.

Plus I like having a volume reference for each copy of my data.

-----Original Message-----
From: EMC NetWorker discussion [mailto:NETWORKER AT LISTSERV.TEMPLE DOT EDU] On
Behalf Of Curtis Preston
Sent: Tuesday, September 02, 2008 1:42 PM
To: NETWORKER AT LISTSERV.TEMPLE DOT EDU
Subject: Re: [Networker] Query in Staging from adv_file

>I do not want to get into the situation where the VTL has copied a 
>virtual tape (VT00001) out to a physical tape
(VT00001) 
>and then NW recycles that tape in the VTL and uses it again.  NW has
now 
>lost track of the data that is on the physical VT00001.    

This is a red herring, IMHO.  In any integrated VTL worth its salt, this is
done with barcode matching:

1. You put physical tape LT00001 into the physical library (PTL) 2. VTL
inventories PTL, finds LT00001 3. VTL adds LT00001 to inventory of VTL 4. NW
backs up to LT00001 5. VTL sees LT00001 is full, copies it to real LT00001
5. NW ejects LT00001 from VTL, triggering eject of real LT00001

When you're done, NW thinks it copied to LT00001, and thinks it ejected it,
and that's what happened.  If you expire/recycle LT00001, there won't be any
difference from what happened if the tape was physical from the start.

>If you can keep NW from ever recycling the virtual tapes so that it 
>never loses track of the data on the physical tapes then you'll be ok.

Again, this is no different than physical tape.  Why would you be expiring a
tape that has backups on it you want?

>Much easier (in my mind) to have NW stage the data from the virtual 
>tapes to a different physical tape.  Doing that means that you can have

>small virtual tapes and large physical tapes and not waste tape media 
>and according to recent discussion here

It's easier IF YOU CAN DO IT.  What might stop you?  Two things.

First, in the VTLs I've tested, there is sometimes a significant performance
difference between the copy speed of a backup-software-managed copy and a
VTL-managed copy.  (It has to do with the makeup of the backups on the tape.
If there are a lot of files in it, or if there are a lot of small
incremental images, the copy can take a lot longer if you do it via the
backup software.)  I had one customer that tested the alternative, and found
it to be about 20 times faster in his environment to have the VTL make the
copies.

Second, it's not like it's easy to automate making clones in NW, especially
in large environments.  If you're good at scripting, you can make it happen.
If you're not, this is still NW's Achilles' Heal.  BUT, if you want to just
back up to virtual tape, have those virtual tapes become physical tapes, and
then send those physical tapes offsite, you can do that with no scripting --
if the VTL supports copying to physical tape.

>...increase performance on the VTL

Completely disagree based on what I've seen.

>...and decrease the risk of virtual tape contention.

Again, I don't see where this is an issue.






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