File balancing, what's it all about?

We get a lot of questions around file balancing, here we answer the most common ones.

What is the purpose of file balancing? The simplest answer is that it allows for drives within a pool to maintain the maximum amount of free space possible. This can be important on systems that run duplication, as each file write operation must have two drives that can accommodate the file being written. Often, when a file is written to a drive (either a standard Windows drive or a Drive Bender pooled drive), Windows will not know the final size of the file being written, the application creating the file simply writes until it is done, and then closes the file. In such cases, balancing ensures that we have at least two drives that can be used for the target file.

Is balancing important on a pool that does not use duplication? No, if you are not running duplication, balancing serves little purpose. In fact, we recommend disabling balancing on systems that

1. Do not run any duplication
2. Some duplication on a small number of files
3. Some duplication on rarely modified files
4. Your pool is static in nature (i.e. not a lot of writes or deletes)
5. You have ample free space

Is there a downside to enabling balancing? Yes, there are a number of potential issues

1. The most obvious is wear and tear on the drives... when background balancing happens, there can be many reads and writes, if balancing is not a requirement, this is a waste of system resources, and added drive wear.
2. There is an overhead to balancing that consumes CPU and drive resources.

I'm running duplication and my pool refuses to balance, what's happening? This issue is more pronounced on systems with a lower number of pooled drives, and a high number of large files. Basically, Drive Bender is unable to move specific files because the preferred, target location contains the duplicate version of the same file (or vice versa). With existing versions of Drive Bender, we limit the amount of effort spent trying to resolve file locations during balancing, however, we are looking to improve this with either v3.2 or v4.

For more detailed information on balancing, and some of the more advanced balancing features, see the Advanced file balancing article.