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)