WAFL NetApp

SUBHANSHU BHATTSUBHANSHU BHATT
2 min read

What is WAFL?

WAFL, or Write Anywhere File Layout, is a proprietary file system developed by NetApp for its storage appliances. It is designed to support large, high-performance RAID arrays, enable quick restarts without lengthy consistency checks after a crash or power failure, and allow rapid filesystem growth.

Why WAFL is 4KB in Size?

In NetApp, FC and SAS drives uses 520-byte sectors and each 4KB block is made up of eight sectors. The last 8 byte is reserved for the BCS.

Note: Here BCS means, Block Checksum that is used to ensure data integrity by detecting corruption in stored data blocks. When data is written to a disk, a checksum is generated and stored alongside the data. Upon retrieval, the system recalculates the checksum and compares it to the stored value—if they match, the data is intact; if not, corruption is detected.

Therefore, 520-bytes now becomes 512-bytes that when multiplied by the 8 becomes 4096-bytes that is the size of NetApp's WAFL Block.

In SATA drives, NetApp uses BCS 8/9 checksum methods to basically format the disk. This means that each 4KB block is made up of 9 sectors out of which only 8 sectors are used to store the user's data. This same is used in the case of the SSD which again uses the 512-bytes sectors to store the data.

Additionally, there are some factors or reservations in NetApp:

  1. 10% WAFL system reserve.

  2. 5% aggregate snapshot reserve.

  3. 20% default volume snapshot reserve.

This is how WAFL block in NetApp is calculated. For more information or deep dive in this topic do comment. I will go deeper dive in this topic.

Thanks!!

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Written by

SUBHANSHU BHATT
SUBHANSHU BHATT

My focus is on managing and configuring cutting-edge storage solutions, including NetApp and Dell EMC. We've enhanced data protection and integrity through innovative tools like Snapshot and Commvault, ensuring robust client support. My educational foundation in Information Technology from Maharshi Dayanand University complements my hands-on experience, where I've honed skills in NAS and VMware ESXi. These competencies, paired with AWS certifications, drive my commitment to excellence in storage administration.