cant create virtual disk greater than 256gb

[mark_a_k]

hi, i ma trying to creat a virtual harddisk for a windows 2003 vm on ESX 3.5. When i attempt to create the hard disk at 555gb i receive a message stating that the size is above the parameters and then the highest size i can create is 256gb. Is there a limit on the size of a virtual hard disk on a VM?

Thanks.

[Troy_Clavell]

by default when you present a LUN to a server the block size is 1MB, which only allows up to a 256GB HDD for any VM. The only way I know how to present a new LUN with a bigger block size is to format it and present with a differnt block size

1MB=256GB

2MB= 512GB

4MB= 1024GB

8MB= 2048GB

[DAbowitt]

Troy is absolutely correct. Ran into this yesterday when trying to create a LUN for my File Server. We are just getting up and running on ESX and SAN. So I created a clone of my Gold VM and when tried to add a HD for D drive it only presented me with option with up to 256MB. After research I then set block size to 4MB and was able to create a 1TB LUN.

[mark_a_k]

what are the effects of changing the block size? is there is performance hit on the volume or any other advantages/disadvantages?

thanks again

[Kahonu84]

A bounce to see if anybody has a reply to Mark's question

[lmonaco]

From what I've seen, there is no noticeable I/O performance gain/loss by using a different block size. The only disadvantage I see is that your smaller files take up more space.

[Dave_Mishchenko · Accepted solution]

Smaller files won't actually take up more room due to sub-block addressing and as you state the performance is the same - http://communities.vmware.com/thread/47171.

[lmonaco]

Thanks for the clarification Dave, didn't know about the sub-block space.