Basic questions around policies and schedules
Updated: 26 Jan 2012 | 14 comments
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I have a couple of basic questions, just to clear up a few annoyances I have.
Question 1
Could someone give me a good example as to why you are able to set the multiplexing level in a schedule as well as the storage unit? And if possible provide an example why these two might differ? It’s just not clear to me as to why some schedules might have a different multiplex settings from schedules in other policies that use the same storage unit.
Question 2
If move a client from one policy to another, will this first backup this client does in the new policy be a full no matter what the schedule says? And is this the only case where this might happen?
Many many thanks
JB
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Hi - hope this helps: 1. The
Hi - hope this helps:
1. The maximum multiplexing is set on the drive but you may want to restrict this per client or policy so it can be reduced in the schedule - it can also then load balance usage across policies in that way. The maximum number of jobs per client (Master Server Host Properties - General tab; and also Client Attributes [max jobs this client]) can also affect this. Note also that the multiplexing level set in a schedule has no effect when backing up to disk so does not restrict the number of backup jobs that run when backing up to disk - that is set on the disk Storage Unit only (weel, apart from the maximum number of jobs per policy on the Policy attributes tab)
2. If you move a client to a new policy it will run which ever schedule is due, however, if it is in Incremental schedule it will backup the entire server as it has no Full backup to compare it to - and will continue to do so until it runs a Full Backup schedule. Best to manually run (or schedule) a full backup as soon as it is placed into a policy. Many policy changes can cause this to happen such as path changes and schedule changes so always best to make changes on a Friday afternoon (or which ever is nearest to your Full backup window)
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Thanks for both responses.
Thanks for both responses. This helps a lot.
I guess I'd like to know an example situation why you might want to reduce the multiplexing level on the schedule?
Suppose you have multiple
Suppose you have multiple clients with low processor power or bandwidth available. You'd want only 1 stream to start from each client, but you would want them to simultaneously write to 1 tape drive. Multiplexing on the schedule would be 1, but say 5 on the drive.
That way you can keep the drive going at an acceptable rate and not damage it.
Regards,
Riaan Badenhorst
ITs easy ;)
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1. Think of it this way. What
1. Think of it this way. What you set on the storage unit is the maximum mulitplexing you'll allow per the drive/media. What you set on the schedule is what you actually want to use for the client, number of streams you want the client to produce (for that policy). Like Mark said, all the settings combined allow you to control how the streams are distributed across the tape drive and vice versa, how the data arrives from the source.
Regards,
Riaan Badenhorst
ITs easy ;)
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The schedule MPX value limits
The schedule MPX value limits jobs that can run to a drive - so when that policy kicks in a starts writing to a drive it is restricted to that many streams on that tape.
An example would be if you wanted one server to always write on its own tape - by using a schedule with MPX of 1 and starting that policy first it would take a drive and set its MPX to 1. No other jobs would be able to join it in using that tape.
It can also be used to load balance policies in this way
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Explained in a loooot of
Explained in a loooot of detail http://www.symantec.com/docs/DOC2799
Regards,
Riaan Badenhorst
ITs easy ;)
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Thanks a lot to you both.
Thanks a lot to you both. Very helpful indeed :)
I may be wrong but the answer
I may be wrong but the answer you have marked as the solution is not actually correct.
If a drive has an MPX of 5 but the schedule has an MPX of 1 for the slow policy and 4 for the fast policy these two will not be able to write to the same drive to create the total of 5 streams.
If any schedule has an MPX of 1 it will take a drive and no others will be able to join it regardless of the MPX setting on the drive - as per my earlier post
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I agree with Mark
If you have a slow client and you only want THAT client to run 1 job at a time - that is set in Client_attributes in the master server properties - by setting it here the client can only run 1 job at a time - but the schedule/policy can still run multiplex to the tape.
Now the difference between a Storage unit and the policy can be:
when you have multi policies that use the same storage unit but might use different volume pools - or even the same volume pools.
say one policy has the majority of your normal clients and uses a storage unit with 6 drives
and you have a policy that does databases - some people want fast restores on the database backup so they don't want to multiplex -
so you have 6 drive in the SU with multiplex at 6
the client policy uses that storage unit and volumepool A - and you set the policy to multiplex 6
but your database policy has a multiplex of 1
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the thing is there are so many ways to look at it and use it - all based on what you want to do or can do
in the above example you could also have the databases using a different storage unit that is set to 1
I don't have to know how to spell....I work on Unix.
NetBackup 7.0.1 - AIX & Windows
Thanks J.Hinchcliffe. In
Thanks J.Hinchcliffe. In your example, if the schedule with a multiplex setting of 1 was to begin first, then this would lock down the drive to only one stream, even though the storage unit has a multiplex setting of 6 other schedules of a higher multiplex setting would wait until this job finishes.
And if this was the other way round, whereby if the schedule with a higher multiplex setting was to begin first the schedule with the multiplex setting of 1 would queue.
JB
kind of yes
the schedule with a multiplex of 1 only need 1 tape then only 1 tape drive would be locked down. If the storage unit had 6 drives the other 5 could be used by other policies. If however the first policy was allowed to use all 6 tape drives (and had enough jobs) they it would put 1 job to each of the 6 drives and it they all would lock down.
if the schedule that has a multiplex of 6 started first and had enough jobs to use all 6 drives then the jobs that are only allowed to multiplex only 1 would have to wait for a free drive before it could start.
I don't have to know how to spell....I work on Unix.
NetBackup 7.0.1 - AIX & Windows
You are correct - as
You are correct - as hopefully I have explained during my posts - they do tie each other down a bit - it is always the lowest figure that governs the number of streams going to a tape
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Thanks Mark, updated
Thanks Mark, updated solution.
After some testing it seems it’s not always the lowest figure.
If policy A is has a schedule with a multiplex setting of 4 and policy B has a multiplex schedule setting of 6 (let’s say the storage unit has one drive with max streams set to 10)
If policy A runs first it will use a max of 4 streams. When policy B starts it will only be able to start a max of two streams adding up to the total of 6 streams. In this case the highest schedule multiplex setting in policy B dictates the overall max amount of streams to the drive, between these two policies.
However, if policy A has a schedule multiplex setting of 1, and policy B’s schedule multiplex setting remains at 6 then as you explained above, if policy A starts first it will use its maximum of 1 stream. When policy B begins it will NOT start any streams until policy A is complete due to the setting of 1 in policy A’s schedule.
JB
Thanks That's pretty much
Thanks
That's pretty much what I was saying - glad you had the chance to try it out in practice - it is a nightmare to explain in words and so much easier to understand when you see it for yourself
Glad to have helped
Mark
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