Understanding Storage Systems: Components, Structures, and Performance, Essays (high school) of Computer Networks

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Storage System Environment

Module 1.

Module Objective Upon completion of this module, you will be able to:  (^) List components of storage system environment

• (^) Host, connectivity and storage  (^) List physical and logical components of hosts  (^) Describe key connectivity options  (^) Describe the physical disk structure  (^) Discuss factors affecting disk drive performance

Host  (^) Applications runs on hosts  (^) Hosts can range from simple laptops to complex server clusters  (^) Physical components of host

• (^) CPU
• (^) Storage  (^) Disk device and internal memory
• (^) I/O device  (^) Host to host communications  (^) Network Interface Card (NIC)  (^) Host to storage device communications  (^) Host Bus Adapter (HBA) Laptop Server Mainframe Group of Servers LAN

Host: Logical Components Host DBMS HBA HBA^ HBA Applications Volume Manager Operating System File System Device Drivers

Logical Components of the Host: LVM  (^) Responsible for creating and controlling host level logical storage

• (^) Physical view of storage is converted to a logical view by mapping
• (^) Logical data blocks are mapped to physical data blocks  (^) Usually offered as part of the operating system or as third party host software  (^) LVM Components:
• (^) Physical Volumes
• (^) Volume Groups
• (^) Logical Volumes (^) Physical Storage Logical Storage LVM

Volume Groups  (^) One or more Physical Volumes form a Volume Group  (^) LVM manages Volume Groups as a single entity  (^) Physical Volumes can be added and removed from a Volume Group as necessary  (^) Physical Volumes are typically divided into contiguous equal- sized disk blocks  (^) A host will always have at least one disk group for the Operating System

• (^) Application and Operating System data maintained in separate volume groups Logical Disk Block Volume Group Physical Disk Block Physical Volume 1 (^) Physical Volume 2 Physical Volume 3 Logical Volume Logical Volume

Logical Components of the Host (Cont)  (^) Device Drivers

• (^) Enables operating system to recognize the device
• (^) Provides API to access and control devices
• (^) Hardware dependent and operating system specific  (^) File System
• (^) File is a collection of related records or data stored as a unit
• (^) File system is hierarchical structure of files  (^) Examples: FAT 32, NTFS, UNIX FS and EXT2/

How Files are Moved to and from Storage 1 2 3 5 4 Mapped by (^) LVM to Teacher (User) Course File(s) (^) File System Files File System Blocks LVM Logical Extents Disk Physical Extents Configures/ Manages Residing in Reside in Mapped by a file system to Managed by disk storage subsystem

Connectivity Protocol

 Protocol = a defined format for communication between sending and

receiving devices

• (^) Tightly connected entities such as central processor to RAM, or storage buffers to controllers (example PCI)
• (^) Directly attached entities connected at moderate distances such as host to storage (example IDE/ATA)
• (^) Network connected entities such as networked hosts, NAS or SAN (example SCSI or FC) Tightly Connected Entities Directly Attached Entities Network Connected Entities

Popular Connectivity Options: PCI  (^) PCI is used for local bus system within a computer  (^) It is an interconnection between microprocessor and attached devices  (^) Has Plug and Play functionality  (^) PCI is 32/64 bit  (^) Throughput is 133 MB/sec  (^) PCI Express

• (^) Enhanced version of PCI bus with higher throughput and clock speed

Popular Connectivity Options: SCSI  (^) Parallel SCSI (Small computer system interface)

• (^) Most popular hard disk interface for servers
• (^) Higher cost than IDE/ATA
• (^) Supports multiple simultaneous data access
• (^) Used primarily in “higher end” environments
• (^) SCSI Ultra provides data transfer speeds of 320 MB/s  (^) Serial SCSI
• (^) Supports data transfer rate of 3 Gb/s (SAS 300)

Storage: Medias and Options  (^) Magnetic Tape

• (^) Low cost solution for long term data storage
• (^) Limitations  (^) Sequential data access, Single application access at a time, Physical wear and tear and Storage/retrieval overheads  (^) Optical Disks
• (^) Popularly used as distribution medium in small, single-user computing environments
• (^) Write once and read many (WORM): CD-ROM, DVD-ROM
• (^) Limited in capacity and speed  (^) Disk Drive
• (^) Most popular storage medium with large storage capacity
• (^) Random read/write access  (^) Ideal for performance intensive online application

Lesson: Disk Drive Upon completion of this lesson, you will be able to:  (^) List and discuss various disk drive components

• (^) Platter, spindle, read/write head and actuator arm assembly  (^) Discuss disk drive geometry  (^) Describe CHS and LBA addressing scheme  (^) Disk drive performance
• (^) Seek time, rotational latency and transfer rate  (^) Law’s governing disk drive performance  (^) Enterprise flash drive

Disk Drive Components Interface Controller Power Connector HDA