Windows Knowledge Base

[VMAX] Understand VMAX Virtualisation layers

A block is the smallest unit on a disk drive
-520 Bytes block size
-512 Bytes for data
-8 Bytes for meta-data (CRC)
A track is a logical build of 128 blocks on a disk drive
-64KB  track size
A cylinder is a logical build of 15 tracks on a disk drive
-960KB cylinder size
Each disk drive is formatted with multiple cylinders
Each disk drive is then sliced into up to 512 slices also called hyper-volumes-extensions (256 on DMX4)
-A slice maximum size of 240GB (64GB on DMX4)
Different slice size can exist on the same disk drive
To simplify LUN allocation, it is recommended to divide the disk deviceinto slices of the same size

A hyper-volume (nickname “hyper”) is a logical volume made of multiple slices/HVE from different drives and provides RAID protection
- Create your hyper across different loops ==> no single point of failure at a director level
- Create your hyper across engines ==> no single point of failure at an engine (drawer ) level
- To simplify LUN allocation, it is recommended to Create a group of physical disks with the same characteristics (capacity, type & rpm), same slice size, across...
1). Different Device Enclosures but using the same disk position/slot (0 to 14) in each DE
2). Different loops
3). Different engines (if you want your hyper to survive an engine failure)

A meta-volume (nickname “meta”) is made of 2 or more hyper-volumes/logical-volumes
- Can concatenate or stripe hyper-volumes across loops and directors/engines for performance
- Maximum size of 16TB size
- Maximum of 255 devices/hyper-volumes