Nachos 2 – Extra Points

Equipo:Carlos Eduardo Triana Sarmiento

Jonathan Alvarado MataObed David Guevara Ibarra 

CacheCache memory is a type of memory, cache memory saves all data that computer needs to work.

But was not the RAM?

Well, partly yes. The computer's  main memory(RAM) and cache memory are basically the same in many respects, the difference is the use that is given to the cache.

The main feature of the cache is very fast, about 5 or 6 times the RAM.

The cache can be a reserved area of main memory, like a high-speed storage.

Two types of cache:• Cache: a memory of high speed static RAM• Disk cache

The cache is effective because the programs access again and again to the same data or instructions.

Keeping this information in SRAM, the computer avoids accesing main memory.

The cache acts as a summary of data RAM, and we all know that a 500 page summary is not at all useful.

The ideal size depends on the RAM and the following table shows it:

RAM(Mb) Cache(Kb)

1 a 4 128 o 256

4 a 12 256

12 a 32 512

mas de 32 512 o 1024

Hard Disk Drive

Hard Disks are coated whit a thin magnetic layer, usually of iron oxide.

Cylinders: concentric circles starting at the outside and end on the inside.

Tracks: These are the lines of the disk.

Sectors: Each track on the disk is divided in sectors.

Cluster: Is the length of the track taken as a processing unit in each read or write to the disk, which is equivalent to the length of a sector on floppy disks or set of 4 or 8 contiguous sectors on disk hard.

To write, head is positioned over the cell to record and passed through it a current pulse, which creates a magnetic field on the surface.

When reading data from disk is passed over the area that is required and will detect a magnetic field as found magnetized in one direction or another, indicate whether the position is stored in a 0 or a 1. 

In writing case is reversed, the head is a current which causes a magnetic field and depending of the sense of this place a 0 or 1.

Drive size (MB)

FAT type (bits)

Sectors per cluster

Cluster size (KB)

0-15 12 8 4

16-127 16 4 2

128-255 16 8 4

256-511 16 16 8

512-1023 16 32 16

1024-2048 16 64 32

Latency on a Hard DiskThere are a number of factors related to speed hard drives to understand its operation.

• Time track search• Speed of rotation• Access time average

Latency: time it takes for the needle to be placed in the desired sector 

Transfer rate: rate at which data (bits) can be transferred from disk to the central unit. It depends on the rotational speed and density data storage on a track

The latency depends on the speed of rotation and is equal to half the time it takes to describe the disk full turn.

Some of the fastest models now have disks that rotate at 10000 rpm more to reduce latency.

rpm 1 turn every latency

3699 16,66 mseg 8,33 mseg

4500 13,33 mseg 6,66 mseg

5400 11,11 mseg 5,55 mseg

7200 8,33 mseg 4,16 mseg

10000 6,00 mseg 3,00 mseg

Solid State Drive

A solid state drive or SSD (Solid State Drive) is a data storage device that uses a nonvolatile memory such as flash memory or a volatile memory such as SDRAM, to store data, instead of turntables found in magnetic hard drives. Solid

state drives have a lower access time and latency.

They are easily interchangeable without having to use adapters or expansion cards to make them compatible with

the equipment. 

  Advantages

• Faster startup, having no need to take courses at a constant speed.

• Great write to speed.

• Faster reading, even 10 times more than traditional hard disks through internal RAIDs on the same SSD. 

• Low latency read and write.

• Application launch and boot in less time. Results of the faster read speed and especially the search time. But only if the application resides in flash.

• Lower power consumption and heat production. Result of having no mechanical elements.

• No noise: The same lack of mechanical parts makes them completely inaudible.

• Resistant: Can withstand falling, shock and vibration without spoiling and without uncalibrated. 

• More secure and unrecoverable deleted data. 

    Limitations:

• Price: The flash memory prices are considerably higher in price / gigabyte, the main reason for low demand. However, this is not a technical disadvantage. 

• Low recovery: After a physical failure data are completely lost because the cell is destroyed.

• Capacity: They have less capacity than a conventional hard drive, which reaches more than three Terabytes.

• The number of read and write cycles of these units is reduced as reducing the size of the memory transistors, so the latest have a lower total lifetime.

SATA vs ATA

A SATA hard drive is an electromechanical device that is responsible to store and read large volumes of information at high speeds.The ceramic disks are mounted on a shift that rotates at high speeds.

Such disks have a feature called "Hot swappable", which means it can connect and disconnect without turning off the computer.

The ATA standard was originally designed ton connect hard disks, however, developed an extension called ATAPI (ATA Packet Interface) interface that allows other storage peripherals (CD-ROM, DVD-ROM drives, etc) in ATA interface.

The SATA hard disk can have two measures:

• 3.5 inches (3.5"), for internal hard drives for desktop computers.

• 2.5" internal hard drives for laptops (Notebook).

Unit is the byte, but currently used measures like Gigabyte (GB) and Terabytes (TB). For SATA HDD this data can be 80 GB to 400 GB.

NTFS File System

NTFS (New Technology File System) is a file system included in Windows NT versions of Windows 2000, Windows XP, Windows Server 2003, Windows Server 2008, Windows Vista and Windows 7.  It is based on the HPFS file system from IBM / Microsoft, and also has some influences from the HFS file format designed by Apple.

NTFS allows you to define the cluster size, from 512 bytes (minimum size of a sector) independently of the size of the partition.

FAT 16 File System

This is the file system introduced by Microsoft in 1987 to support 16bit files. It was designed originally to handle files in a "floppy drive".

This file system has a very important set of limitations, among which the maximum of 2GB partition, using cluster 32Kb or 64Kb and not support long names files.

FAT16 does not support compression and encryption.   

Fuenteshttp://www.conozcasuhardware.com/quees/memcache.htm

http://www.pchardware.org/discos/discoacceso.php

http://www.monografias.com/trabajos14/discosduros/discosduros.html  

http://es.wikipedia.org/wiki/Unidad_de_estado_s%C3%B3lido#Ventajas

http://sistemas.itlp.edu.mx/tutoriales/admonarch/tema1_7.htm