Fibre Channel (FC) is a high performance interface designed to boost performance and the flexibility of storage systems with multiple drives.
Fibre Channel has several key benefits:
- Hot Pluggable -- drives can be installed or removed while the host is running.
- Performance -- the fastest interface in multi drive environments.
- High data integrity
- Longer cable lengths -- relative to LVD
- Cost effective -- other high end solutions require expensive adaptors
- Longer cables -- FC is 30m over copper and 10km over optic fibre while the total length for LVD is 12m
- Data redundancy -- frames include a CRC while SCSI simply relies on parity
- Dual Loop capability -- Allows two servers to be connected, one on each loop, at the same time so servers can share a drive without any manual switching
With five drives or less, FC offers no performance benefit over LVD. However, as the number of drives grow above five, so does the performance advantage of FC. FC currently peaks at 100Mbytes/sec while LVD stops at 80Mbytes/sec. A FC loop can also cope with up to 126 devices compared to LVD's 15 device limit. A dual FC loop, therefore, can accommodate up to 252 drives but there is a caveat. If two servers are connected to the DAS -- one per loop, there can be 252 devices provided the servers do not share any drives. Each shared drive accounts for a single device in both loops. So if all the drives are shared between two servers a dual loop can only support a maximum of 126 drives.
