CIS 527

File Servers Overview

File Server

• Provide storage to other devices
• Share files and data between systems
• Protect information based on users/groups
• Backups, redundancy, security, and more

Storage Disks

• One or more rotating platters
• May include cache memory
• Used to store "blocks" of data
• Must be formatted before use

Disk Formatting

1. Low Level Formatting / Initialization
2. Partitioning
3. High Level Formatting (File System)

Low Level Formatting

• Creates disk sectors and tracks on the disk
• Disks prior to 1990s required LLF
• Newer disks have LLF done at the factory
• Disks can also be reinitialized

Disk Partitioning

• Subdivide a single physical disk
• Partions can have different formats
• Easier to manage backups, caching, logging, etc.

High Level Formatting

• NTFS - New Technology File System
• FAT32 / exFAT - File Allocation Table
• HFS / HFS+ - Hierarchical File System
• ext3 / ext4 - Extended File System

Access Technologies

• SCSI / iSCSI
• PATA / IDE
• SATA

Small Computer System Interface (SCSI)

• Data transfer standard for phsycially connected computers and peripherals
• Used with hard drives and tape drives
• Rarely used today on consumer devices
• iSCSI (Internet SCSI) allows using SCSI commands via TCP/IP

Parallel AT Attachment (PATA)

• Used interchangeably with Integrated Drive Electronics (IDE)
• Standard for storage device connections
• Commonly used for internal connections
• Largely replaced by SATA in 2000s

Serial AT Attachment (SATA)

• Replaced older standards in mid 2000s
• Allows hot swapping, native command queuing (NCQ) through the Advanced Host Controller Interface (AHCI)
• Up to 6Gbps throughput
• External SATA (eSATA) allows use outside devices

Redundant Array of Independent Disks (RAID)

• RAID 0 - Striping
• RAID 1 - Mirroring
• RAID 5 - Striping and distributed parity
• RAID 6 - Striping and double distributed parity
• RAID 10 - Mirroring & Striping

Server Message Block (SMB)

• Sometimes called Common Internet File System or CIFS
• Widely used by Windows operating systems
• Completely reverse engineered to create the SAMBA project

Network File System (NFS)

• Used by many Linux systems for network access
• Supported by most Unix/Linux distros
• Open standard allowing anyone to use

Network Attached Storage (NAS)

• Device speficially designed to be a networked file server
• Typically uses several drives in a RAID configuration
• Makes data available at the filesystem level using CIFS, NFS, AFP, etc.

Storage Area Network (SAN)

• Dedicated network of devices that provide block level data storage
• Typically on a separate, fiber-optic network
• May consist of multiple servers / drive bays
• Uses protocols such as iSCSI or Fibre Channel Protocol (FCP)

What does a File Server do?

• Abstract away all details of the storage implementation
• Provide a client-facing interface to the storage
• Manage quotas, access rights, etc.
• Handle load balancing

Storage Virtualization

• Insert a layer of virtualization between the file access and block-level storage
• Allows easy migration, use of heterogeneous systems, simpler management, etc.
• Adds complexity & support risks

Assignments

• Lab 6 - Application Servers: Due Monday 4/18 11:30 AM