Louwrentius

If you want to order a new iMac with an SSD there are two problems:

1. An SSD of 256 gigabytes will cost you a lot: 600 euros.
2. The SSD is of medium quality, and does not justify the cost of 600 euros.

Here you can find information about the Toshiba SSD that Apple provides.

You can consider buying an SSD for half the price and put it inside your new iMac yourself afterwards. However, this is a hassle and you will probably void your waranty.

The solution is to buy an SSD yourself and put it in an external Firewire 800 casing. Firewire 800 provides you with about 70 megabytes per second of troughput, which is enough for most applications. It is about three times faster than USB and the latency of Firewire is lower than that of USB, thus improving responsiveness.

Thunderbolt would provide the best solution, but as of July 2011, there are no Thunderbolt products on the market.

The product I use is an external 2,5 inch Firewire 800 casing of OWC: the Mercury Elite-AL Pro mini. This casing cost me about 60 euros or 80 dollars including shipping costs. I admit that this solution is not cheap, but it does work. And you won't void your warranty and it is way cheaper than the Apple SSD.

I've put my Intel SSD inside this casing and my mac boots in about 15 seconds. After entering username and password, login is almost instantaneously.

Caveat

I encountered one problem with the OWC casing. I encountered random system freezes, related to the external OWC housing. Using the internal 1 TB hard drive, I had no problems. The cause of this issue is probably related to power not being provided to the OCW casing after the systems returns from sleep.

I resolved this issue by connecting a special USB cable to the iMac and connecting the other end to the 5V DC Power Input on the OWC casing. After that, the daily random system freezes vanished. These cables can be obtained almost everywhere.

Intel and Apple released Thunderbolt a high-speed (10 Gigabit/s) interface, that seems to replace both USB and Firewire. It is mainly targeted at end-user systems allowing to connect peripherals with just a single cable to a computer. Thunderbolt devices, like external hard drives or displays can be daisy chained, like Firewire. In short, Thunderbolt removes the cable clutter and ads a significant speed bonus.

For NAS owners and storage enthusiasts, this is also a very interesting technology. Just like Firewire, it seems to support computer-to-computer communication. So Thunderbolt could be used as a high-speed link between your homegrown NAS device and your PC workstation. Or between two storage / server system.

The only downside to Thunderbolt is the maximum cable length of 3 meters between devices. Thunderbolt doesn't seem to be the ideal replacement for your Gigabit network, but if most of your computer systems are close to each other, it might be very interesting.

Update: I found this interesting story about getting two Infiniband cards + cable. These are 10 Gbit cards and the author shows that 700+ MB/s transfer rates (as in megabytes) is possible.

This is my NAS storage server based on Debian Linux. It uses software RAID and 20 one terrabyte hard drives. It provides a total usable storage capacity of 18 terrabytes in a single RAID 6 array.

One of the remarkable side effects of using 20 drives within a single array is the read performance of over one gigabyte per second.

Nowadays you can buy a 1 TB harddrive for less than 100 euro's . So I build myself a 4 TB NAS box, which is already 50% full. However, although it is to some degree fault-tollerant by using RAID 6, one mistake or catastrophic hardware faillure and all data is lost.

And that's where the 'problem' start. For every € spend on storage, you may need another € to secure that storage.

You can choose to take and accept the risk outlined earlier and not to make backups. However, if you do want to make backups of terrabytes of storage, how are you going to pull that off without too much cost? 

In my opinion, the only reliable and usable solution is to build a second NAS box and sync the two. Ideally, both machines reside at different locations, but hey, I'm talking about a home solution, not a professional environment. Although you might ask why on earth you need 4 TB of space at home in the first place.

Anyway, the point I'm trying to make is that although storage in itself is cheap, if you want to keep all that data safe, storage is far more expensive than you might think.