01-22-2013 08:51 AM
I'm curious about how NetBackup decides which media servers should be used for SLP duplications.
We have 2 Data Domains which we back up to, with a total of 4 media servers; these servers are then grouped in load balanced pairs. Generally our policies are set up so that one pair writes backups to one Data Domain while the other pair deal with the backups for the other Data Domain. However, all 4 media servers can access both Data Domains.
Looking at many of our SLP duplication jobs, the "Media server" listed in the detailed status is something along the lines of:
"exampleserver1 -> exampleserver2" (with each server being from a different pair as described above)
However, I have noticed that when the environment is busy overnight, any running SLP duplications often use the same server to read and write the image (e.g. "exampleserver2 -> exampleserver2"). Is this simply because the other servers are busier so NetBackup doesn't assign two different media servers for the duplication job?
Solved! Go to Solution.
02-06-2013 04:16 AM
If the duplications / replications are using Opt Dup then it doesn't really matter which media server it uses as the actual process will go from de-dupe appliance to de-dupe appliance, the media server is just an incidental part of the process as it doesn't actually do anything
In general when you setup a Storage Server then in the credentials secton you have all media servers included within it as having access to it (first tab labelled Media Servers).
You find that if all are selected it will use any to do replications
The -required option is about the only way to prevent that happening in my experience other than unchecking the other media servers in this credentials section
01-22-2013 09:28 AM
hi,
its because of the Network Optimized Duplication feature.
see the highlited once below
01-22-2013 09:32 AM
https://www.google.co.in/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&ved=0CDEQFjAA&url=http%3A%2F%2Fwww.symantec.com%2Fbusiness%2Fsupport%2Fresources%2Fsites%2FBUSINESS%2Fcontent%2Flive%2FTECHNICAL_SOLUTION%2F75000%2FTECH75047%2Fen_US%2F334042.pdf&ei=Wsn-UMC6LeOP8gG9lIGIBQ&usg=AFQjCNHGLMu4Kja7p6cu7d-R1RTXCevCyg&bvm=bv.41248874,d.b2U
01-22-2013 10:00 AM
I think it's this one :)
01-23-2013 05:03 AM
Thank you for the replies - that's some useful info. So it's preferable for the same media server to be used?
Does NetBackup have to involve the media server that wrote the original backup when it duplicates? As I explained, all 4 of my media servers can access both Data Domains so even if the original backup server is busy, could NetBackup not use another idle media server to read and write for the duplication? Or is this what using the required option would achieve?
Looking at the default option of Network Optimized Duplication feature ("If the media server is busy or unavailable, NetBackup uses a different media server" in particular), I seem to be getting the opposite for many of my duplications. I checked some SLP duplications that ran when the environment was either very quiet or had no jobs running at all, and it still used 2 different media servers for the duplication in most cases. Very confusing! Or have I misunderstood the default option?
If it is preferable for the same media server to be used for read and write (and a delay in resource allocation isn't a problem for me), should I consider running the "nbemmcmd -changesetting -common_server_for_dup" command to use the preferred or required option?
01-23-2013 05:17 AM
hi,
as you are saying "checked some SLP duplications that ran when the environment was either very quiet or had no jobs running at all, and it still used 2 different media servers for the duplication in most cases."
by any chage alternate read server is selected in SLP?
please use Preferred option and see how its works.
nbemmcmd -changesetting -common_server_for_dup preferred -servername master server name
01-24-2013 07:19 AM
I've double checked and we definitely don't have an alternate read server selected on any of our SLPs.
Just out of interest, why do you recommend the preferred option over the required option? Also, can anyone advise on my other questions from above?
Does NetBackup have to involve the media server that wrote the original backup when it duplicates? As I explained, all 4 of my media servers can access both Data Domains so even if the original backup server is busy, could NetBackup not use another idle media server to read and write for the duplication? Or is this what using the preferred/required option would achieve?
Thanks for your help so far.
02-05-2013 05:29 AM
Have a look at this TN: http://www.symantec.com/docs/TECH87200
DOCUMENTATION: Restores and duplications from OpenStorage backup need not use the same media server that wrote the backup.
Solution:
1. In most cases creating this touch file on the master server will force Open storage backups to use the media server that did the backup.
02-06-2013 04:00 AM
Thanks for the response Marianne - I'll take a look.
02-06-2013 04:16 AM
If the duplications / replications are using Opt Dup then it doesn't really matter which media server it uses as the actual process will go from de-dupe appliance to de-dupe appliance, the media server is just an incidental part of the process as it doesn't actually do anything
In general when you setup a Storage Server then in the credentials secton you have all media servers included within it as having access to it (first tab labelled Media Servers).
You find that if all are selected it will use any to do replications
The -required option is about the only way to prevent that happening in my experience other than unchecking the other media servers in this credentials section
02-06-2013 06:04 AM
Ok, that's good to know. With regards to the media server not doing anything during an optimised duplication, I'm guessing it's only involved as part of the initiation of the job if it isn't involved in moving any data?
All of our media servers are listed for each storage server, exactly as you described. From the above, I'm still unsure if it's actually preferable for one media server to do both reading and writing for a duplication - although I'm guessing this is irrelevant for optimised duplication?
How can I confirm if we're using optimised duplication? DD Boost is licensed and enabled on the Data Domains and we're using v2.5.0.3 of the OST plugin on our media servers. This is actually something else on my list of things to look into and address in our environment!
02-06-2013 06:52 AM
I believe DD Boost and DD in general is supported for OPT DUP - so data will go from DD to DD - all part of the OST-Plugin
04-02-2013 01:08 AM
Thanks for the help everyone - I eventually found that OST Opt Dup wasn't being used in our environment due to our use of Storage Unit Groups. After checking with Symantec support, I restructured our DD Storage Units and SLPs and confirmed that Opt Dup is now being used.