VM added second disk (useable space issue)

[digitalex]

Any reason why when I add a secondary disk to a virtual machine and the actual disk is 299.5GB. It will only let me add it the VM as 254GB? It will not let me add it as 299, 290, or 280GB? I have another VM that has 110GB and it using 109GB of the 110 fine. The block size is 1mb.

[Dave_Mishchenko · Accepted solution]

When you use a block size of 1 MB the maximum size of a VMDK is limited to 256 GB. To add a VMDK file larger than 256 GB you would have to format the datastore with a block size of 2 MB (vmdk file up to 512 GB) / 4 MB (1024 GB) or 8 MB (2048 GB). You can't change the block size without a reformat.

[digitalex]

You are right I missed the part where it said maximum disk size 256. Doh. Thanks.

[Dave_Mishchenko]

A warning message that explains things better would probably be helpful in cases like this. Going with 2 MB isn't going to be an issue, but you will want to leave some free space depending on what else you have on the LUN. For example, if you plan to use snapshops then you'll need to leave space for that , etc.