Compared to tape-based solutions, a backup system with hard drives is as low maintenance as it gets. Of the 576 hard drives, only three failed in the course of twelve months - that's a failure rate of 0.53%. The RAID controllers automatically restore the array using the hot-spare drive. The administrator then simply has to exchange the defective hard drive.

We believe that more drives, proportionately speaking, will give up the ghost at the end of the five years, but that's not that big a deal, financially. Dr. Koch has given a five-year warranty on the backup system - quite a promise, considering Maxtor has only guaranteed the drives for three years. As we mentioned before, the system has been up for only a year.

Nevertheless, the prices for IDE drives are dropping so quickly that you should be able to buy replacement drives for a song. Also, you could reorganize individual RAID 5 arrays if a large number of hard drives fail or if you wish to add more capacity. Were we to set it up today, the backup system could start with 576 x 250 GB; that's equal to 144 TB gross or 108 TB net. Dr. Koch has set the maximum size at 100 nodes for now, which would add up to 450 TB net.

The high performance is also a plus for the backup customer: backups and recoveries can be performed at today's top speed, provided there is enough network bandwidth available.

The backup system's cost was some $435,000, including tech support and five years' warranty - but that was the cost in January of 2002. Today, a similar system would be much cheaper or would offer more storage capacity.