Version 1.4 aggregates

For a version 1.4 aggregate, the architected maximum size for compatibility mode aggregates is approximately 4 TB (1 KB x 4 GB). If you use 3390 DASD that has 65,520 cylinders per volume, you can create a compatibility mode aggregate of about 2,850,088,550,400 bytes.

65520 cylinders per volume
x 90 blocks per cylinder
x 8KB per block
x 59 volumes
--------------------------
2654 GB or 2.59 TB

Restriction: A zFS version 1.4 compatibility mode aggregate is limited to 4 TB even on extended address volume (EAV) devices. A zFS version 1.5 compatibility mode aggregate is limited to 16 TB even on extended address volume (EAV) devices.

The maximum number of objects (files, directories, and ACLs) in a zFS file system is 4 G. The maximum size of a file is approximately 4 TB. The maximum size of a directory is 4 GB. There is a limit of 65,533 (64K -1) subdirectories in a directory for a v4 directory. There is a limit of 4,294,967,293 (4G-1) subdirectories in a directory for an extended (v5) directory. The maximum number of names in a directory is dependent on the length of the names. However, there is a known performance problem when you have a large number of names (hundreds of thousands or millions) in a single zFS v4 directory. For best performance, use an extended (v5) directory in a version 1.5 aggregate. See Using version 1.5 aggregates and extended (v5) directories for information about extended (v5) directories. If you must use a version 1.4 aggregate because you are still running releases prior to z/OS® V2R1, try to spread names among many directories.

Do not use version 1.5 aggregates until you are sure you will not run any releases before z/OS V2R1.