Analysis

posted on 17 April 2008 07:56

Tiger Technology recently announced shared file access to a storage area network (SAN). I asked the company how its MetaSAN product could do this. Was it a network-attached storage (NAS) head? Here is the reply from Bernard Lamborelle of Tiger Technology:

There are three types of SAN:

1. LUN Masking: each computer connects to a dedicated LUN, part of the same RAID (group).  There is no sharing.

2. Volume-level sharing: multiple computers connect to the same LUN, but only one computer has R/W access, others only have Read access.

3. File-level sharing: every machine has full R/W access to the same LUN

A NAS shares direct-attached storage over the LAN. As such, any metaSAN client, can become a NAS head. In this case, multiple NAS will share access to a common SAN storage. 

Since each NAS has a group of clients connecting to it, there are risks of I/O bottlenecks and hot spots. If that NAS fails, these clients loose access to the shared storage. 

Using metaLAN (as an agent software on the clients), and metaSAN on the NAS heads, the individual servers can be virtualised, and clients connects to the "cluster of servers". They benefit from failover and automatic load balancing.

^{[Chris Mellor.]}