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  • Latest Post - ‏2013-07-25T12:28:20Z by RDzJohn
2 Posts

Pinned topic EAV Support

‏2013-07-22T18:26:17Z | eav mod223

Hello -

Does the latest z1090 code support EAV volumes?  We are planning to use mod223s but would like to check before doing so.


  • RDzJohn
    302 Posts

    Re: EAV Support


    RD&T does support EAV volumes but not as specific device types.  You must create the volumes by specifying number of cylinders.

    eg.   alcckd WORK01 -d3390 -s66633

    If more than 65520 cylinders (for a 3390) are specified, an extended address volume (EAV) is produced. The number of cylinders in an EAV should be an even multiple of 1113.

    While RD&T does allow the definition and use of EAV volumes, it is not recommended for the following reasons:

    - all IO operations on RD&T are emulated.

    - all IO devices on RD&T are emulated.

    - RD&T does not support multi-pathing or PAV access to storage devices.

    - each RD&T volume is represented as a single linux file.

    - each RD&T volume is managed by its own linux process.

    - RD&T serializes access to storage on a volume basis.  This means datasets created on large volumes managed by a single linux process are much more likely to encounter currency issues, especially for multi-write scenarios.

    - RD&T reserves the entire file size for 3390 device types.  This means a linux file representing an EAV device of size 66633 cylinders will consume approximately 55.68 GB on disk, regardless of how much of the emulated disk is actually in use.

    For the above reasons, we recommend the use of smaller volumes with RD&T.