Storage Networking
Storage Trends
• Storage growth
• Need for storage flexibility
• Simplify and automate management
• Continuous availability is required
Storage considerations
• Capacity
• Performance
• Scalability
• Availability and Reliability
• Backup and recovery requirements
• Support/staff needs
• Budget
RAID
• Consolidate multiple physical disks into a logical grouping
• Designed for fault tolerance and performance improvement
• Can be implemented in H/W or S/W
• Several RAID levels exist
Hardware RAID
• Volume Management performed by RAID controller
• Parity computation performed by the RAID controller – decreases server overhead
• Dedicated cache memory improves server performance
Software RAID• Performed by the server O/S
• Parity computation performed by the server – increased overhead
• RAID performance depends on the server performance and CPU load
• For simple environments with lower performance and availability requirements
Simple levels of RAID
• RAID 0 – Striping• RAID 1 – Mirrored Volumes• RAID 2 – Bit-level striping with parity distributed to
one or more disks• RAID 3 – Byte-level striping with dedicated parity
disk• RAID 4 – Block-level striping with dedicated parity
disk• RAID 5 – Block-level striping with distributed parity• RAID 6 – Block-level striping with distributed
double parity
Nested RAID
• RAID 0+1: striped sets in a mirrored set
• RAID 10 (or RAID 1+0): mirrored sets in a striped set
• RAID 5+1: mirrored striped set with distributed parity (also known as RAID 53)
• RAID 5+0: striped set of RAID-5 sets
Block-level vs File-level access
• File systems 2 views:
1. Data representation to users/applications (hierarchical view)
2. Storage organization (data structure)
• Block-level access: write/read blocks; master/slave relationship
• File-level access: using file names; client/server relationship
DAS
SCSI protocol
Block-level accessFile system is on the server
DAS
NAS
IP Network
IP Network
Clients
Servers
File Protocol: SMB/CIFS, NFS, etc.
File-level access to the outside; block-level to the storage subsystemFile system is on the NAS device
NAS
SAN
Servers
SCSI over Fibre Channel
Storage Area Network
Block-level accessFile system is on the server
SAN
IP Storage• Traditional SANs used Fibre Channel
protocol and storage technology to connect SAN at gigabit speeds
• SCSI commands transmitted over FCP
• Expensive
• Requires dedicated network equipment/architecture
IP Storage• As an alternative, existing IP infrastructure
can be used
• FCIP, iFC protocols allow Fibre Channel devices to be connected over IP networks
• iSCSI allows SCSI commands to be encapsulated to be transferred through an IP network
iSCSI• Allows SAN utilize TCP/IP for block-level
data transfer
• Transport for SCSI commands
• Existing networks (routers/switches) can be utilized – no need for special equipment
• With current network technologies supporting gigabit speeds, comparable to FC in speed
NAS-SAN Integration
Distributed File Systems
• SMB/CIFS; Samba (Windows-based systems)
• NFS (Unix-based)
• AFS (Unix)
• AFP (MAC)
• NCP (Netware)