You can enable free space reallocation on aggregates to improve write performance. Free space reallocation improves write performance by optimizing the free space within an aggregate. Free space reallocation is disabled by default.
When to enable free space reallocation
Free space reallocation works best on workloads that perform a mixture of small random overwrites and sequential or random reads. You can expect additional CPU utilization when you enable free space reallocation. You should not enable free space reallocation if your storage system has sustained, high CPU utilization.
When to use free space reallocation with other reallocation features You can use free space reallocation with the other reallocation features that you use to manage system performance: reallocation scans and read reallocation. However, you should not run an aggregate reallocation scan (reallocate -A) if free space reallocation is enabled on the aggregate.
How free space reallocation differs from an aggregate reallocation scan
Like an aggregate reallocation scan (reallocate -A), free space reallocation optimizes the location of blocks in an aggregate. However, an aggregate reallocation scan is a one-time scan of every segment within an aggregate, while free space reallocation runs continuously and scans only the segments to be used.