After reinstalling VMWare ESXi server, how can I attach existing VMFS partitions?
I looks like the only way to do this is to have them formatted, and I'd really like to keep the existing data already on them.
I just did this today (4.0, not 3.5). I had an existing disk with a single VMFS3 partition filling the whole disk. That partition was a datastore all by itself. After installing ESXi 4.0, I plugged the disk back in and rebooted. On boot, the new (well old) datastore was under /vmfs3/volumes/ automatically.
Assuming it's ESXi 3.5, you need to run a rescan on the storage adapter with the attached devices.
You might get away with just going into VI Client, then Configuration, Storage Adapters, right clicking on the relevant one and hitting "Rescan".
If that works, great, if not you probably need to set the EnableResignature setting, but that's not a trivial process so instead I'll link to someone else's description of the task