Is it possible to create a 3390-54 volume for zDT?

It looks like only 3390-3 and 3390-9 will work.  I tried 3390-54, but it defaulted back to a 3390-9.

I successfully migrated 3390-54 volumes with the DASD migration tool from our prod LPAR and they work fine within the zDT. 

Thanks.

Hi

This is the syntax:

alcckd <volser> -d3390 -s65520

When you initalize the disk, you should use these parameters;

VTOC 0,1,2024    

Index 135,0,405

If you use the normal parameters (0.1.74    5,0,30) most of the disk will be unreachable.

Br Michael Erichsen,

Xact Consulting

Hello,

You can define a 3390 Mod 54 volume in a zD&T environment using the -s option on the alcckd command and Michael has provided the syntax of how to do that. 

While there is no harm in using a cylinder size of 65520 in an emulated environment, there are issues with using this sizing in real Storage hardware (like DS8xxx hardware). The problem when using real storage controllers is the fact that CKD volumes are created using fixed sized extents. Each extent is 1113 cylinders in size, so if one creates volumes that are not a multiple of 1113 then you end up wasting space.

For example:

To define a volume of size 65520 cylinders you need about 58.87 extents (65520/1113)

Since the storage hardware cannot allocate partial extents, this would be rounded up to 59 Extents.

So every volume of size 65520 cylinders would waste 0.13 extents or 144.69 Cylinders (1113 * 0.13). While this doesn't sound like much, it amounts to significant waste when you are defining 100's or even 1000's of volumes in a large Storage subsystem.

On real Storage hardware volume sizes should be based on multiples of 1113:

Mod 3 - 3339 Cylinders

Mod 9 - 10017 Cylinders

Mod 27 - * should be 30051 in order to remain a multiple of 1113

Mod 27's, for some reason became commonly known to have a size of 32760 and I believe the reason for this was that at some point in History the maximum size of a CKD Disk was 32760 cylinders. These volumes then became known as a Mod 27. A Mod 54 was then dubbed as twice the size of a Mod 27 which then translated to 65520 (32760 * 2).  A Mod 27, defined as 32760 Cylinders, wastes even more space than a Mod 54 @ 65520.

Ultimately, if you ever plan on moving your emulated volumes onto non-emulated hardware then you should use the same volume sizes defined at your installation on the real z storage hardware so you don't run into size mismatches.

Thank you, Greg.

It is nice to have values based on something real and optimal.

I will change my own standards accordingly, but I doubt that any auditor will ever allow anyone to upload a ZD&T volume to the Big Iron???

Would you change the IKCDSF INIT parameters too, or are they fine?

Br Michael Erichsen,

Xact Consulting

You can in fact create any size emulated disk of a multiple of 1113 cylinders by just using the -d parameter, i.e.

alcckd /disks/mod54 -d3390-54                      this will create a disk of 1113*54 - 60102 cylinders

AWSCKE088I Typical model values are 1, 2, 3, 9, and A. Model value specified was 54
AWSCKE035I Creating file '/zdisk/mod54', 3390, 60102 cylinders

AWSCKE005I Processing file '/zdisk/mod54' ...
AWSCKE006I    Device type: 3390-9
AWSCKE009I      Cylinders: 60102, heads 15
AWSCKE010I     Track size: 56832

alcckd /disks/cyls20 -d3390-20                      this will create a disk of 1113*20 - 22260 cylinders

AWSCKE088I Typical model values are 1, 2, 3, 9, and A. Model value specified was 20
AWSCKE035I Creating file '/zdisk/cyls20', 3390, 22260 cylinder

AWSCKE005I Processing file '/zdisk/cyls20' ...
AWSCKE006I    Device type: 3390-9
AWSCKE009I      Cylinders: 22260, heads 15
AWSCKE010I     Track size: 56832

To create a 3390 EAV  use the -A parameter:

alcckd /disks/mod954 -d3390-A -s65520             this will create a 3390-EAV with 65667 cylinders, a model 59 if you like

AWSCKE005I Processing file '/zdisk/mod54' ...
AWSCKE006I    Device type: 3390-A
AWSCKE009I      Cylinders: 65667, heads 15
AWSCKE010I     Track size: 56832

As you see, the -s parameter is ignored. In order to create a non-standard size with the -s parameter, just use -d3390

There was a bug in the 1.8 version of z1090/z1091 which would not allow you to do some of these functions, it has been fixed in the 1.9 version.

If the number of cylinders that you specify is not an exact multiple of 1113 cylinders, then some space in the last allocated extent is wasted. For example, if you define 1114 or 3340 cylinders, 1112 cylinders are wasted. For maximum storage efficiency, consider allocating volumes that are exact multiples of 1113 cylinders. In fact, multiples of 3339 cylinders should be considered for future compatibility. If you want to use the maximum number of cylinders for a volume (that is 1,182,006 cylinders), you are not wasting cylinders, because it is an exact multiple of 1113 (1,182,006 divided by 1113 is exactly 1062). This size is also an even multiple (354) of 3339, a model 3 size.

Sebastian