02/02/2018
SAN (Technologies, Protocols, Design)
- A network of Storage devices
- Seperates storage from the server
- Benefits:
- High I/O Ratings
- Server Failover
- Shared / Pooled storage
- Lower TCO ( compared to direct storage)
SAN Components
- Host Bus Adapter
- Interfaces the device to the network
- Datastorage
- The drives within the san ( SAN speed + Uptime + Enterprise grade)
- Storage Subsystems
- RAID Settings ( Performance ~ Redundancy )
Protocols and Standards
- SCSI
- Older standard protocol, server / drive communication.
- Parrallel Bus Standard
- Half duplex
- 16 device daisy chain
- Fibre channel
- 16 million device support
- Speeds up to 4Gbps and now 128Gbps.
- 10KM distance without extenders
- Multiprotocol support
- Fibrechannel is not Ethernet
- Speedratings: 1,4,8,16,32,128Gbps
Fibre channel Communications
- Very similar to TCP
- Point-to-point session establishment ( 3-way handshake like)
- Logical node connection point ( like TCP ports )
- Fibre Channel Protocol ( FCP ) Supports flow control using ‘Buffer Credits‘ ( TCP Windows)
- Multiple Sessions per device ( TCP Sockets )
- Cisco MDS 9000 series switches design for this job.
Fibre channel Virtual SANs
- A virtual SAN (VSAN) provides VLAN-like capabilities to a ‘SAN Island
- Connections between switches ( ISL )
- Cisco MDS 9000 uses Enchanced ISL
- Inter-VSAN Routing ( IVR ) connects VSANS at Layer3. (Used with Fibre channel over IP (FCIP))
- Parallel Universe; Fabric Shortest Path First ( FSPF ) Zoning.
REF:
San Design
- Similar to switch designs only on smaller scale
- Cisco SAN MDS 9000
- First Gen, Stackable Switches
- Second Gen, Modular switches (less ISL , Redundancy)
Extending Fibre Channel
- Within datacenter – Multimode / Single mode fiber
- Metro – Dense wave Division Multiplex ( DWDM )
- Anywhere – Fibre Channel over IP ( FCIP )
- NOTE: ISCSI supports SAN extention over tcp/ip ( Not over Fibre Channel )
- FCIP connects SAN to SAN, iSCSI connects Hosts to SAN
- QoS absolutely needed for non-dedicated links.