[summary unexpected_eckd_block_size]
There are ECKD DASDs with non 4k block size &summary;

[explanation unexpected_eckd_block_size]
There are ECKD DASDs that have a block size other than 4096 bytes.

Measurements showed that a block size of 4096 Bytes (4KB) shows the best results for I/O throughput and free disk space after formatting the DASD. Further tests showed that this statement is independent to the request size issued by the application.

The following DASDs have non-4K block sizes:

&details;

To confirm, run the "lsdasd" command to display DASDs and their block sizes.

[solution unexpected_eckd_block_size]
To low-level format a DASD with a 4096 bytes block size, complete these steps:

 1. Backup existing data that resides on the disk.
 2. Low-level format the disk with a block size of 4096.
    For example, you can use the "dasdfmt" command
 3. Restore the backup to the disk. Depending on your backup applications,
    you might format the disk with a new file system first.

[reference unexpected_eckd_block_size]
See the man pages of the "lsdasd" and "dasdfmt" commands.
