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 access File system is on the server

DAS

NAS IP Network Clients Servers File Protocol: SMB/CIFS, NFS, etc. File-level access to the outside; block-level to the storage subsystem File system is on the NAS device

NAS

SAN Servers SCSI over Fibre Channel Storage Area Network Block-level access File 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)