How much free disk space should I leave on a vmware ESXi 4.0 host

I have VMWare ESXi 4.0 installed (not embedded) on a server.  datastore1 holds 2 wirtual machines on it currently, and reports about 9.5 GB free out of 131GB total disk space.

I wish to virtualise an XP machine that runs our telephone software. Currently this has a disk of about 9.5 GB.
Can I safely use all the space on datastore1 or should I leave some free space available?
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You should always leave some disk space.
You currently have less than 10% free on your datastore - I wouldn't consider that space for any use.

When a VM starts, it uses diskspace temporarily and this is the equivalent to the amount of memory that the VM has allocated to it (it's actually a bit more scientific than that, but for the purposes of this - it's close enough).  So unless you can run your XP VM with about 3gb of disk, forget about using the datastore.

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nappy_dThere are a 1000 ways to skin the technology cat.Commented:
You need to consider swap space for the guest machines. If your guest OS is using 4GB of ram you need to leave that much space. This is true for every machine that is in the VMFS store.

You also need to leave room for logging and snapshots.

My rule is 15-20% of total space.
andy_beltonAuthor Commented:
Thanks. I will use datastore2 which has ample space available.
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