You would need to setup a VM to present the storage as iSCSI/NFS to the other host(s)...
Personally, I wouldn't do it. IF you need more storage/space, then get an actual SAN/NAS and have shared storage. You'll gain additional benefits from having the storage independant of the hosts. Not the least of which it won't matter if the host that has that storage is online, or not, to use it. If this is a lab configuration, then you could go with something fairly cheap, such as a QNAP array. If this is in a work/production environment/configuration, then you'll want something more robust, reliable, and with a solid support structure. You'll also want to use a RAID level that will not bugger you if you lose a drive, or two.
In my experience, work/production environment storage needs to be online 24x7. Even if there are times when the array won't be accessed (maintenance windows) it's best to have something that can stay online 24x7. I have a QNAP array in my home lab that's been running for a few years now (24x7) and has only had a single drive failure (5 drives, set up in a RAID 5 array). Fortunately, I had planned that I could have a drive go south, so I had a spare on hand. Since they were still under warranty, I was able to get a replacement drive (to replace my cold spare) easily.
