When creating or configuring LUNs or shares, we've added an option named Auto Defrag. Auto Defrag keeps data fragmentation down without needing to defragment the entire volume on a scheduled basis. Defragging reduces the number of extents on files by rewriting and combining data in free volume space, which eases performance problems when reading files with large numbers of extents scattered across the file system. Extents are added when there are many in-place modifications to files.
Auto Defrag is use-case dependent and should not be enabled in all cases. Auto Defrag briefly waits for you to finish writing to a file and lower your existing IO operations before it activates.
Take into consideration which shares or LUNs you will be enabling this function on and determine if automatic defragmentation or scheduled defragmentation is right for you.
- If you write to the same file 100 times a day, the ReadyNAS would defrag this file 100 times.
- If this is the case, you may just want to consider defragging on a scheduled basis, as perpetually defragmenting files can increase CPU and disk IO.
- Virtual Machine images, databases, and iSCSI LUNs are mechanisms constantly updating single files on ReadyNAS.
- Improper configuration may lead to performance degredation.