AIX Ver. 4 SysAdmin IV:Storage Management (Unit 1) – Introduction to Storage Management

Unit Objectives:
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– Understand the storage management option available for the RS/6000
– Describe the considerations that go into making informed decisions when selecting storage devices.

Storage Management Considerations (1 of 2)
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SCSI, ESS, SSA
RAID, JBOD – Just a bunch of disks
Random or Sequential
Cashe
Parallel or Serial
Hot Swappable
SAN

Storage Management Considerations (2 of 2)
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Cost per megabyte – speed, capacity
Access frequency – number of I/O requests per gigabyte
Access density – number of I/O requests per gigabtye
Access type – sequential or random
Data rate – number of I/O requests per gigbyte
Online life – how rapidly data is accessed (once found)
Interchange requirements – data age – how long to be accessible
Longevity – archives, backups, integrity of data
Reliability – security of mission critical data

Hardware Attachment Adapters
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Main considerations when looking at adapters:
– Cabling Requirements
– Performance/Reliability
– Addressability
– Device Support
– Cost

Small Computer Systems Interface (SCSI) Subsystems
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SCSI – pronounced “scuzzy”
Universal, intelligent disk-drive interface
Industry-standard interface widely used in medium and large systems
Supports not only disks, but tapes, CD-ROM, scanners and other devices as well
Features high-transfer speeds, flexibility, as well as advanced functions such as command queuing
Supports up to 15 devices.

Serial Storage Architecture (SSA) Subsystem
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Tower models 500, 600 and T40
Drawer models 010, 020, and D40

Enterprise Storage Architecture (ESS or “Shark”)
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Cages/Disk Arrays
DC Power Supplies
RISC Processors & Device Adapters
Host Adapters
Fans/AC-Power
Rack Batteries

High Availability Cluster Multi-Processing (HACMP)
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Clients
Public LAN
Multiple Nodes
Disk Buses
Shared disk with mirrors
HACMP Cluster

Other Storage Management Concepts (1 of 2)
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Storage Area Networks (SAN)
-High-speed network, comparable to a LAN, that allows the establishment of direct connections between storage devices and processors. A SAN can be shared between servers or dedicated to one server is local, or extended over geopraphical distances. They are used to connect shared strage arrays to multiple servers.

Fibre-Channel
– A communications protocol designed to meet the many requirements related to the ever increasing demand for high performance information transfer. It is carried over fiber optic as well as coper cables. It’s purpose is computers, storage devices, and other peripherals.

JBOD (Just a Bunch of Disks)
– A simple disk subsystem where the disk drives are accessed individually by the host subsystem.

Redundant Array of Inexpensive Disks (RAID)
– Multiple disk subsystem accessed by the host system as one disk.

Geographic Remote Mirroring (GeoRM)
– GeoRM is a stat-mirroring product that provides a point-to-point method of duplicating the contenct in real-time of any given logical volumes over unlimited geogrphic distances. One traget server can support up to seven source servers.

High Availability Geographic Cluster (HAGEO)
– HAGEO provides real-time mirror of customers data between systems connected by local or point-to-point networks, bringing recovery capability to an RS/6000 cluster placed in two widely separated geographic locations.

Disk Cache
– Disk cache is a solid-state memory on a disk drive that matches the data tgransfer speed differences between high-speed computers and slower-speed hard disks, and is used as a holding area for data being written to or retrieved from a disk, improving performance.

Unit Summary
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The various storage management options that are available for the RS/6000
Several storage management technologies.
Points to consider when selecting storage systems.

FAQ
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Q: What is a bus?
A: A bus is a common pathway, or channel, between multiple devices. It is a set of hardware lines, wires, designed to connect multiple devices. The term was coined after a real bus since a bus stops at all bus stops en route. In an electronic bus, the signals go to all stations connected to it. A computer with an 8-bit bus transfers 8 bits of data at a time, and one with a 16-bit data bus transfers 16 bits at a time.

Q: What is asychronous transmission mode?
A: Asynchronous mode provides for communication with no time restrictions and allows packets of data to be transfered after having a response from the receiving device.

Q: What is synchronous transmission mode?
A: In synchronous transmission, both stations are synchronized. Codes are sent from the transmitting station to the receiving station to establish the synchronization, and data is then transmitted in continuous streams.

Q: What is the difference between serial and parallel transmission?
A: In the serial mode, the bits of data are transmitted sequentially, one after another. In parallel mode, the bits are transmitted simultaneously over several wires. The parallel transmission is faster, but serial is cheaper and more suitable for use over larger distances.

Q: What is a spindle?
A: A spindle is the rotating shaft in a disk drive. In a fixed disk, the platters are attached to the spindle. In a removable disk, the spindle remains in the drive.

Q: What is cache?
A: Cache is specialized RAM used to optimize data transfers between system elements with different performance characteristics. Having certain data stored in cache speeds up the operation of the computer.

Q: What was the first universal, intelligent disk drive interface for UNIX systems?
A: The Small Computer Systems Interface (SCSI) was the first intelligent disk drive interface designed for UNIX systems

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