What is the default behavior for file placement

[Caramon]

I have had DP for almost a year now, but after talking with several folks in the SnapRAID community I'm rethinking my strategy in terms of how files are placed. I had originally set up DP with the OFP plugin to fill up one drive at a time. However a recent update to SnapRAID has shown me that I needed to rethink that, so I disabled the OFP and rebalanced my entire pool of 7 drives to where they are evenly distributed for data/free space.

 

That being said I don't want the Balancer to run all the time shifting files around as that will mess with SnapRAID's ability to restore should something happen between syncs, but instead I just want DP to place new files on the drive with the most free space, but in the myriad of options I'm getting a little lost in how to accomplish that or maybe it already is and I'm just being paranoid. 

 

So a couple of questions:

 

What is the default behavior of DP when placing new files and the balancers disabled?

Is there a threshold that DP adheres to when placing new files on a drive? Say it allows so much % to that drive before moving to the next one with the most free space?

 

I have Automatic Balancing set to Do not Balance

Automatic Balancing options are grayed out

Plug-in settings is checked

File Placement settings are checked

 

On the Balancing Tab I have:

Stablebit Scanner enabled and default

Prevent Drive overfill enabled and set to 97% Full or 100GB free

Duplication Space Optimizer enabled

 

 

[Christopher (Drashna)]

The default file placement strategy is to place new files on the disk with the most available free space.  This is measured in absolute size, and not percentage (for instance, the 3TB with 2TBs free will be used before the 4TB with 1TB free). 

 

So over time, each disk will end up with approximately the same amount of free space.  Though, this can cause issues (for instance, 20x disks with 100GBs free will limit you to adding files that are smaller than 100GB, even if you have 2TBs free on the pool. 

 

 

As for the balancing, I would still recommend re-enabling the other balancers.  For the most part, the software won't rebalance data around a lot, except for in specific conditions. 

But let me specify the balancers and the conditions, so you can make the choice yourself. 

• StableBit Scanner:  Only moves files when damage is detected (when the surface scan detects unreadable sectors). It can be configured to do this when SMART errors are detected, as well. And it can be configured to avoid disks that have overheated.  
• Volume Equalization: This balancer tries to equalize the usage between multiple volumes (partitions) that reside on the same physical disk. 
• File Placement Limiter or Drive Usage Limiter:  This balancer lets you specify if a disk can be used for duplicated and/or unduplicated data.  Useful for prepping a disk for removal, or to only allow duplicated data on a drive, for instance. 
• Prevent Drive Overfill:  This balancer doesn't do anything until the disk gets "X percent" full (the default being 90% full).  Once the disk hits this, the balancer will try to move content off until it is only 85% full.
  This can be configured to be more or less aggressive, as well to specify specific sizes (defaults to 100GBs for the trigger, and 200GBs as the goal. 
• Duplication Space Optimizer: This does a number of things, but it's main duty is to get rid of the "Unusable for Duplication" space.

 

As for the balancing settings, it may still be best to keep on on balancing automatically. especially if the balancers that you're using are not excessively active.  And the "Balance immediately" option as the option to set the number of hours between balancing passes. The default being 12 hours, but you can set this to any number up to 744 (31 days).  This may be more suitable, in the long term. 

[Caramon]

Thanks for the clarifications, that's the info I was looking for.

[Christopher (Drashna)]

You are very welcome!

 

If you have any more questions, don't hesitate to ask.