Memory and physical storage

Unit objective: Identify memory characteristics and

install storage devices

Topic A

Topic A: Memory Topic B: Storage devices

Memory

RAM: random access memory Working area for data during

processing Need sufficient RAM for

– Performance– Software support

Quality of RAM is important

Measuring memory

Cells– Store a single bit of data– 0 or 1– Represents on/off or yes/no

Measurement units – Bit– Nibble = 4 bits– Byte = 8 bits– Word = based on CPU

32-bit processor: 32-bit word 64-bit processor: 64-bit word

Larger memory units Byte (B) = 8 bits Kilobyte (KB) = 1024 bytes = 210 bytes Megabyte (MB) = 1024 KB = 220 bytes Gigabyte (GB) = 1024 MB = 230 bytes Terabyte (TB) = 1024 GB = 240 bytes

Memory types

Classify memory as:– Volatile vs. non-volatile– Static vs. dynamic– Asynchronous vs. synchronous

Volatile vs. non-volatile memory

Volatile: Loses contents without power Non-volatile: Keeps contents without power

RAM Volatile Random access memory

CMOS Volatile Complementary metal oxide semiconductor

ROM Non-volatile Read-only memory

PROM Non-volatile Programmable read-only memory

EPROM Non-volatile Erasable programmable read-only memory

EEPROM Non-volatile Electronically erasable programmable read-only memory

Flash Non-volatile

Dynamic vs. static memory

Dynamic (DRAM)– Must be continually refreshed– Inexpensive– Physically small chips

Static (SRAM)– Refreshing not required– More expensive– Larger– Faster

Typical uses– Main system memory: DRAM– Cache memory and CMOS: SRAM

Asynchronous vs. synchronous

Asynchronous– Not synchronized to system clock– Consistent time to access and read data

Synchronous– Synchronized to system clock– Accesses data and returns in one or

more clock cycles

SDRAM faster than ADRAM

Memory access typesDRAM Dynamic RAM Older technology

FPM Fast Page Mode Improved over DRAM

VRAM Video RAM Dual port, optimized for video

EDO Extended Data Out Improved over FPM

BEDO Burst Extended Data Out Adds pipelining to EDO

SDR SDRAM

Synchronous DRAM Interleaving permits overlapped requests

DRDRAM Direct Rambus DRAM 16-bit memory bus and two transfers per clock cycle

continued

Memory access types, continuedDDR SDRAM

Double Data Rate Double transfer rate of SDR SDRAM with two transfers per clock cycle

DDR2 SDRAM

Double Data Rate 2 Double transfer rate of DDR SDRAM with four transfers per clock cycle

DDR3 SDRAM

Double Data Rate 3 Double transfer rate of DDR2 SDRAM with eight transfers per clock cycle

Access time

Latency Memory speed

– Nanoseconds vs. megahertz

Overall speed– Doesn’t include latency

Bandwidth

Packaging Early PCs used individual DRAM chips

continued

Packaging, continued

Package– Small circuit board– More commonly called a module– Installed in slot

Module contains– Memory chips– Connecting wires– Support chips– Pins or edge contacts

Single- and double-sided modules

Early DRAM had chips on just one side

Double memory by placing chips on both sides

Double-sided modules have two rows of pins at bottom– Pins on front aren’t connected to pins on

back

Number of chips no longer has a 1:1 chip-to-bit limit

Package types

SIMM 30-pin – ADRAM

SIMM 72-pin – ADRAM

DIMM 100-pin – printer SDRAM DIMM 168-pin – SDR SDRAM

DIMM 184-pin – DDR SDRAM

DIMM 240-pin – DDR2– DDR3

continued

Package types, continued

RIMM– 184-pin – 16-bit– 232-pin – 32--bit

MicroDIMM 144-pin SODIMM 144-pin – SDR SDRAM

SODIMM 200-pin– DDR– DDR2

SODIMM 204-pin – DDR3 SDRAM

30 pin SIMM

72 pin simm

168 pin dimm

184 pin ddr

240 pin ddr2

Ddr and ddr2 difference

240 pin Ddr3

RIMM

sodimm

Modules and chips

PC100 and PC133 use SDRAM PC1600, PC2100, PC2700, and

PC3200 use DDR SDRAM PC2-3200, PC2-4200, PC2-5300,

PC2-6400, and PC28500 use DDR2 SDRAM

PC3-6400, PC3-8500, PC3-10600, PC3-12800, PC3-14900, andPC-17000 use DDR3 SDRAM

Memory error recovery

Parity — Detects an error– Even– Odd– Mark– Space

ECC — Detects and corrects an error Desktop memory — No parity or ECC Server memory — Often includes

parity or ECC

Parity

9 chips,supportsparity

8 chips,no parity

Topic B

Topic A: Memory Topic B: Storage devices

CDs

Recordable CDs CD drives CD drive speeds

DVDs

DVD media DVD storage capacities

Blu-Ray discs

Blu-Ray disc specifications Recordable Blu-Ray

Optical drive installation

Connectors Drivers

Using optical drives

CD software Playing DVD and Blu-Ray discs

Hard disk drives

Components Solid-state drives (SSDs)

Hard disk installation

Chassis Cables and connectors Power cable

Fault tolerance

Ensure continued operations RAID

– RAID 0– RAID 1– RAID 5– RAID 01– RAID 10

RAID considerations Level-specific considerations

RAID levels

RAID level 0– Striping with no other redundancy

features

RAID level 1 (Mirroring)– Simple disk mirroring

continued

RAID

Redundant Array of Independent Disks– Previously Inexpensive disks– RAID 1, 3 and 5 are most common

See http://www.acnc.com/raid

RAID levels, continued

RAID level 1 – different type– Disk duplexing (simple disk mirroring

again but each disk on a separate controller)

continued

RAID levels, continued

RAID level 2 (Stripping)– Data is striped across all disks in the

array disk wear is limited and stripping allows for reconstruction if a drive fails

RAID levels, continued

RAID level 3 (Disk Stripping)– Uses disk striping – Stores error-correcting information– Information written to only one disk in the

array– If disk fails, array cannot rebuild its

contents

continued

RAID levels, continued

RAID level 4– Stripes data and stores error-correcting

information on all drives– Can perform checksum verification

RAID level 5– Combines the best features of RAID– Striping– Error correction– Checksum verification

Windows OS software RAID does not support RAID 2 through to 4

Choosing a RAID level

Boot and system files can be placed on disks configured for RAID level 1, but not for RAID level 5

RAID level 1 uses two hard disks; RAID level 5 uses 3–32 disks

RAID level 1 is more expensive to implement than RAID level 5

RAID level 5 requires more memory than RAID level 1

Reading from disk is faster than write access in both RAID level 1 and RAID level 5

RAID 5 has faster read access than RAID level 1

Striped volume

Reduces the wear on multiple disk drives by equally spreading the load

Increases disk performance compared to other methods of configuring dynamic disk volumes

Mirrored volume

Creates a copy of data on a backup disk One of the most guaranteed forms of

disk fault tolerance Time to write information is doubled If 3 or more volumes are mirrored or

duplexed, RAID 1 is more expensive than other RAID levels

Can’t be striped Requires two dynamic disks Well suited when data is mission-critical

RAID 5

Provides better fault tolerance than a striped volume

Uses disk space more efficiently than a RAID 1 volume

RAID 5 with parity can reconstruct lost data on any disk

Requires minimum of three disks

continued

RAID 5, continued

Performance isn’t as fast as striped volume Reading is as fast Good choice for mission-critical data Parity information based on formula

– 1/n – n = number of physical disks in volume

Software and hardware RAID

Software RAID implements fault tolerance through the computer’s OS

Hardware RAID is implemented through the server hardware and is independent of the OS

Many manufacturers implement hardware RAID on the adapter

Chip on the adapter Battery backup Hardware RAID more expensive

Hardware RAID advantages

Faster read and write response Ability to place boot and system files

on disks with different RAID levels Ability to hot-swap a failed disk More setup options to retrieve

damaged data and to combine different RAID levels within one array

Media cards

SD xD SmartMedia CompactFlash Memory stick

Floppy disk storage

Form factors Capacities Identifying capacities Write protection

Floppy drive installation

Cable Connectors Motherboard connector

Tape drives

Hard drive backups Offsite storage Burst mode Sequential access Compression

Unit summary

Identified memory characteristics and installed storage devices