Home > Data Protection > PowerProtect DD Series Appliances > PowerProtect DD Data Invulnerability Architecture: Enhancing Data Integrity and Recoverability > File system check, if needed, is fast
In a traditional file system, consistency is not checked inline at all. PowerProtect DD systems perform an initial inline verification to ensure consistency for all new writes. The usable size of a traditional file system is often limited by the time it would take to recover the file system after some sort of corruption. Imagine running fsck on a traditional file system with more than 80 TB of data. The reason the checking process can take so long is that the file system needs to sort out where the free blocks are so that new writes do not accidentally overwrite existing data. Typically, this process entails checking all references to rebuild free block maps and reference counts. The more data in the system, the longer the process takes.
In contrast, the Data Domain file system never overwrites old data and does not have block maps and reference counts to rebuild. It only has to verify the location of the head of the log to safely bring the system back online to restore critical data.