[blue68f100]

By looking at this, it apears you have 2 different size drives. Drives 1 and 4 are ~100 gigs, where 2 & 3 are > 137 gig. Opening the unit up will confirm. If I had to guess, drives 2 & 3 are the newer drives (larger). Try to match the capacity of these. Depending on the mfg, some have utilities where you can adjust the capacity so they match. Some users have found it was cheaper to buy higher capacity (>137) than 120 gigs. Knowing that the capacity will be capped at ~137gig.

HD capacity is rapidly changing. If you plan on using this for criticle data, purchase a spare or 2. As you know when you loose a drive in a raid 5 set the data is not lost (normaly), but can not be accesed till the missing member is replaced and the set re-built.