Instruction: Extract information from the supporting document to answer the given question.

Input:
Question: how many thunderbolt ports are available
Document: (In my case I have a Thunderbolt Mac Mini Server connected to it. The drive dwarfs the Mac Mini, that's for sure! )I purchased this when a few became available direct from Amazon, but subsequent to that, Amazon seems to have stopped stocking the drive (it's offered through other resellers). I'm not sure if they're waiting for more to become available or what, but I'd be leery purchasing this drive on-line unless it was sold directly by Amazon, since it's fragile.
If you need a ton of data storage and would like the flexibility of super-fast speeds with RAID-0, this drive will be hard to beat. If you want a high-capacity server for backing up and are willing to mirror the drives for reliability, it's an OK choice too, although if you don't need the highest performance possible it may be better to go with lower-cost FireWire or Thunderbolt drives for backing up.
This product is absolutely incredible! For those of you curious, you can use more than one to have a massive RAID 0 setup on your OSX system. I used two (10 disks total) to make one large 40TB drive. Even with it halfway filled up (18TB used) I'm getting speeds of 700MB+ write and 800MB+ read speeds. On a single thunderbolt cable to my iMac! As long as you have regular backups, there's really no risk.
There's flexibility in how you set it up, although the RAID is software RAID (provided by Mac OS X), and RAID levels other than 0 and 1 aren't possible.I have the drive in a server cabinet so I can't say much about the noise, except it seems quiet and also runs cool. The case is a nice design and rugged.
It just works flawlessly and at insane speeds. It's also the most attractive external enclosure setup I've seen yet and matches the iMac perfectly. It's so artistic I actually put it on my desk to let it stand out.Cons: No hardware RAID. This is a bit disappointing, as I can't use FileVault 2 on it. It's my biggest complaint when dishing out $4500 on this setup.PS: See the screenshot for the speed tests!
I've had the LaCie 5big 20TB for a few weeks now, and while I can't assess the long-term reliability, so far so good. It's definitely fast. The 20TB model consists of five separate 4TB SATA drives. I'm currently running it as a single RAID-0 20TB volume, which offers maximum speed at the risk of data loss (if one of the five drives goes, all of the data is lost since it's striped across them).
Answer: There are two on the unit so they can be daisy chained with other thunderbolt devices.