Thanks again Matthew. Your thoroughness is always appreciated.
In regard to your questions, I'm going to have to get with the backup team
and see if I can get those answers.
On Mon, Aug 1, 2016 at 3:04 PM, Dimensional DBA <dimensional.dba@xxxxxxxxxxx
wrote:
The Oracle advice was only accurate if you used direct attached tape
drives to your servers (circa 1990’s).
As to Seth’s comment on “Shoe Shining”, that only applies to slow writes
to the tape device where the head is having to backtrack to the last write
point over and over again because the stream of data can’t keep up with the
streaming speed of the tape drives. If the streams are maintaining the pipe
to the tape drive itself, then you will not get “shoe shining”.
The math shows 1Gb link, but are your links larger than that from DB
server to Netbackup media server? If it is then yes multiplexing at the
Netbackup side for tape drives can help boost performance. This is where I
originally stated there is architecture and Netbackup tuning that has to be
done.
What version of tape drive do you have?
How many tape drives are dedicated to the Netbackup pool for your backups?
How many tape drivers are attached to each media server?
Intel or AMD architecture on the Netbackup media servers?
How many Netbackup media servers do you have to participate in the backup?
How much free memory is available on the Netbackup media server?
What is the chunk size setting of the Netbackup controlled tape drives.
How are you sending the data via RMAN? Are you simply letting Oracle chunk
the data or are you breaking the database backup apart into manageable
chunks?
No Mladen, there is still a large portion of the world that uses tape
directly for backups except for slow streaming or glitchy data flow backups
(like from many windows servers). Yes there are customers who use disk too.
As to your question Chris
“Let's say we have 6 tapes and he's configured it to do 2 threads per
tape. Does that mean I can open 12 channels in RMAN? I mean, I would
assume so but I have no idea LOL“
Your math is correct but that assumes no one else is performing backups to
those tape drives. This is where you have to work with your Netbackup admin
as to what overall resources are available to you versus the rest of the
backup system to get the optimal flow.
At Amazon we had Netbackup tape multiplexing set to 8 and I have many
clients that use multiplexing at 4 to 6. IT really depends on what
performance you are getting for each incoming stream and how much shared
memory is dedicated to Netbackup on the media servers and number of tape
drives per media server to help maintaining streaming performance to the
drive.
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