The Coma cluster is one of the nearest clusters but it is not the nearest. At a mean distance of about 321 million light years the Virgo Cluster is closer at a mean distance of only 59 million light...
In a computer system, a cluster is a group of servers and other resources that act like a single system and enable high availability and, in some cases, load balancing and parallel processing.
A lost cluster is one that has no FAT or MFT entry pointing to it, and a cross-linked cluster is on the has two or more FAT or MFT entries pointing to it.