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Snapshot pruning recommended setting OS 6.10.4

Labdoc1
Luminary

Snapshot pruning recommended setting OS 6.10.4

Q: is there a best practices setting for pruning or expanding a volume?

 

I am running an upgraded Pioneer Pro with OS 6.10.4. Currently there are 4 disks in a RAID 10 array with 4.23 TB data, 1.24 TB snapshots, and 1.80 TB free space. The warning for pruning is set to 70% - I may have set this number but I do not remember. 

I have room for 2 more disks in the array. Or, I can change the 70% to a higher number.

 

The Netgear "help" is silent on an optimal pruning level https://kb.netgear.com/24478/ReadyNAS-OS-6-Smart-Snapshot-Management

 

Any guidance appreciated

 

 

Model: RNDP600E (ReadyNAS Pro Pioneer Edition)|ReadyNAS Pro Pioneer Edition|EOL
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StephenB
Guru

Re: Snapshot pruning recommended setting OS 6.10.4

I don't think there is an "optimal" setting.  You do want to keep the overall volume free space at at least 10%, otherwise the file system can misbehave.  And there are some situations where snapshots can create a lot of fragmentation in the main share.  A share that holds a live database is one example.  One that is more common for home users is a share used to download torrents.  Generally you're better off turning off snapshots altogether on shares where files are frequently updated in place.

 

Beyond that, it's more about balancing the amount of retention you want to have against the disk space you are using for snapshots.

 

There are two approaches to managing the snapshot use.  One (apparently what you are doing) is to use the "snapshot pruning" setting on the volume settings tab.  Personally I don't use that, I just leave it at the default 90%. 

 

What I do instead is set up my shares to use custom snapshots instead of "smart" snapshots.  My usual settings are shown:

snapshot.png

Using custom snapshots instead of the smart snapshots gives me explicit control over the amount of retention I want to have ("Smart" snapshots actually keep snapshots around forever - until that global threshold you are using kicks in).  As you can see, I just use daily snapshots - of course you can schedule them more frequently.

 

Almost all my shares use the settings above.  But I have one where that holds encrypted PC backup images (it is the destination for my Acronis TrueImage backups), where the amount of space in the snapshot gets large very quickly.  So the retention is set lower there.  And I do have a couple of shares where snapshots are turned off (because the files are updated in place).

 

Then I periodically take a look at the total space used by my snapshots.  If it rises higher than I want it to, then I just adjust the retention downwards (which can be done on a share by share basis).  But I haven't had to do that for a long time.  Even with 3 months retention, I am only using about 3% of file space for snapshots.  Of course the amount you will use will depend on how often you modify or delete files.

 

 

 

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StephenB
Guru

Re: Snapshot pruning recommended setting OS 6.10.4

I don't think there is an "optimal" setting.  You do want to keep the overall volume free space at at least 10%, otherwise the file system can misbehave.  And there are some situations where snapshots can create a lot of fragmentation in the main share.  A share that holds a live database is one example.  One that is more common for home users is a share used to download torrents.  Generally you're better off turning off snapshots altogether on shares where files are frequently updated in place.

 

Beyond that, it's more about balancing the amount of retention you want to have against the disk space you are using for snapshots.

 

There are two approaches to managing the snapshot use.  One (apparently what you are doing) is to use the "snapshot pruning" setting on the volume settings tab.  Personally I don't use that, I just leave it at the default 90%. 

 

What I do instead is set up my shares to use custom snapshots instead of "smart" snapshots.  My usual settings are shown:

snapshot.png

Using custom snapshots instead of the smart snapshots gives me explicit control over the amount of retention I want to have ("Smart" snapshots actually keep snapshots around forever - until that global threshold you are using kicks in).  As you can see, I just use daily snapshots - of course you can schedule them more frequently.

 

Almost all my shares use the settings above.  But I have one where that holds encrypted PC backup images (it is the destination for my Acronis TrueImage backups), where the amount of space in the snapshot gets large very quickly.  So the retention is set lower there.  And I do have a couple of shares where snapshots are turned off (because the files are updated in place).

 

Then I periodically take a look at the total space used by my snapshots.  If it rises higher than I want it to, then I just adjust the retention downwards (which can be done on a share by share basis).  But I haven't had to do that for a long time.  Even with 3 months retention, I am only using about 3% of file space for snapshots.  Of course the amount you will use will depend on how often you modify or delete files.

 

 

 

Message 2 of 3
Labdoc1
Luminary

Re: Snapshot pruning recommended setting OS 6.10.4

Stephen, thank you for the excellent "application note". Very helpful

 

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