Error when using "Add datastore on iSCSI/FC/local SCSI" to create a VMFS 5 LUN"

[Kretschmer]

Hi there,

I want to create a vmfs Datastore using the "Add datastore on iSCSI/FC/local SCSI" Workflow to create a vmfs5 lun.

When I try to create a datastore with the max size which is given during the "Start Workflow" wizard then it will fail. If I choose to create a smaller vmfs size within the disk it runs fine.

Is there a calculation problem inside this standard VMware workflow or am I doing something wrong?

Regards,

Christian

[iiliev]

Hi,

I don't have a suitable environment to validate it, but looking at the scripting code for action com.vmware.library.vc.storage.computeDiskCapacity (which is used in presentation logic of "Add datastore on iSCSI/FC/local SCSI" workflow) it recommends disk capacity using the formula  (return value is size in gigabytes)

    return capacity.block * capacity.blockSize / 1073741824;  

It seems to compute the size of the whole disk, but I suppose there is some amount of 'reserved' space that is not taken into account.

So I'd recommend to use a slightly modified action that assumes some blocks are reserved and returns a slightly lower size, something like

    var reservedBlocks = 2; // not sure how much is reserved
    return (capacity.block - reservedBlocks) * capacity.blockSize / 1073741824;

You can experiment a bit with the value for reserved blocks. I'm not sure how much space is reserved in case of VMFS 5; you can try to search if there is some documentation or google on Internet.