On Wed, Sep 16, 2009 at 7:26 PM, <william.d.brown AT gsk DOT com> wrote:

What are people using for the fragment size on LTO4 (or I guess LTO3) with
NBU 6.x?

I ask because the default is 1TB, i.e. more or less don't fragment.

The argument for a large fragment is that the backup doesn't have to stop
so often as it does briefly at the end of each fragment to update the
Master, and also the inter-fragment file markers waste space..though
that's hardly a consideration on such large tapes now.

The argument for a small fragment was that the tape can position at full
speed to the file marker for the appropriate fragment for a restore,
rather than reading the tar file from the top at read speed, which for a
large tape could be a very long time.

We used to (dating back to DLT7000) set a 2GB fragment, as back then this
was thought a good idea in case you wanted to dd the tape to disk and read
it without NetBackup.  UNIX file systems did not take files > 2GB.  Well I
can't say we ever tried it and it's a silly small size now.

But what are people using - 100GB?  200GB?  Does it really make a
difference...

William D L Brown


-----------------------------------------------------------
This e-mail was sent by GlaxoSmithKline Services Unlimited
(registered in England and Wales No. 1047315), which is a
member of the GlaxoSmithKline group of companies. The
registered address of GlaxoSmithKline Services Unlimited
is 980 Great West Road, Brentford, Middlesex TW8 9GS.
-----------------------------------------------------------

_______________________________________________
Veritas-bu maillist  -  Veritas-bu AT mailman.eng.auburn DOT edu
http://mailman.eng.auburn.edu/mailman/listinfo/veritas-bu

_______________________________________________
Veritas-bu maillist  -  Veritas-bu AT mailman.eng.auburn DOT edu
http://mailman.eng.auburn.edu/mailman/listinfo/veritas-bu