ICT Unit 3 Storage Devices and Media

What is backing up of data? Backing up refers to the copying of file to a different medium It’s useful if in case your main storage is destroyed or set on fire, your data/files are still stored safely Backing up on regular basis is good practice

Why back up data? To safeguard against loss of data due to the failure of the original secondary storage device To safeguard against damage caused by hackers To use files in a different place Backups don’t necessarily guard against the effect of virus

Serial access When using serial access, it’s necessary to access each record from beginning until the required record is found Primarily used on magnetic tape systems When the original master file needs updating, it needs an additional transaction file. It is essential that the records on both files are sorted in the same order The field used to sort the records is called key field

Update process of serial access MF stores data of the products TF stores the changes happened in a day At the end of the day, TF is stored in the same order as the MF The first record in the TF is read and the first record in the MF is read –The two records are compared with each other –If key field on MF < TF, no transactions take place –If key field on MF = TF, new record from TF is written to the NMF –If the transaction file indicates deletion, record is not written to the NMF –If key field on MF > TF, new record is created on the NMF Master File (MF) Transaction File (TF) New Master File (NMF)

Direct access Used with magnetic disks, optical media and solid state media Able to access the data directly from the calculated position Not necessary to sort records in specific order Used when data access speed is vital

Magnetic storage media Magnetic storage media depend on the magnetic properties of certain materials Contains magnetized disks that represent a 1 or a 0 More than one disk are known as platters Each platter is made from glass, ceramic

Fixed / internal hard disk drives UsesAdvantagesDisadvantages Store operating system, systems software and working data/files Store applications software Used in real time systems Used in file servers for computer networks Have a very fast data transfer rate Have very large memory capacities Can be easily damaged Have many moving parts Read/write operation can be quite noisy

Portable Hard Disk Drives UsesAdvantagesDisadvantages Can be used as backup systems systems to prevent loss of data Can be used to transfer data/files/software between computers Data access time and data transfer rate is very fast They have a large memory capacity They can be used as a method of transferring information between They can be easily damaged if dropped or subjected to a strong magnetic field

Magnetic Tapes UsesAdvantagesDisadvantages In applications where batch processing is required where specific processing order is not essential A backup media since all data needs to be stored Used in long term archiving of data Generally less expensive Very robust technology Have huge data capacity The data transfer rate is fast Very slow data access times When updating, another tape is needed Affected my magnetic fields

CD/DVD disks Red laser is used to read and write data CDs and DVDs can be designated: –R – write once only –ROM – can only be read –RW – can be written or read from many times DVD has duel-layering DVDs has more storage than CDs DVD uses 650 nanometers wavelengths, CD uses 780 nanometers

CD-ROM and DVD-ROM UsesAdvantagesDisadvantages Used to store music files, software… DVD-ROMs have a much larger storage Used in applications where preventing the deletion or overwriting of data is needed Hold far more data than floppy disks Less expensive than hard disk drive systems The data transfer rate/data access time is slower than for hard disks

CD-R and DVD-R UsesAdvantagesDisadvantages Home recordings of music and films To store data to be kept for later use Cheaper than RW disks Once burned they are like ROM If finalized, the CD-R/DVD-R can only be recorded on once Not all CD/DVD players can read those disks

CD-RW and DVD-RW UsesAdvantagesDisadvantages Used to record television programs Not as wasteful as R format Used in CCTV systems Can be written over many times Can use different file formats each time it is used Can be relatively expensive It is possible to accidentally overwrite data

DVD-RAM UsesAdvantagesDisadvantages In recording devices such as satellite receivers to allow simultaneous recording Used in camcorders to store movies Have a very long life Possible to do a rewrite operation over times Writing on DVD-RAMs is very reliable Very fast access No need to finalize the disk Very large capacity Offer the ability to read data while data is written Not as compatible as R or RW format Relatively expensive Have been replaced by newer technologies

Blu-ray Disks UsesAdvantagesDisadvantages Home video consoles Storing and playing back movies PCs can use this technology of data storage or back up Very large storage capacity Very fast data transfer rate Data access speed is greater than other optical media Blu-ray disks comes with a secure encryption system Relatively expensive Encryption problems There are fewer movie titles on Blu-ray format

The Future of Optical Media Now, many people store their music on –On hard disk drive systems –In MP3 format –Using the ‘cloud’ so they can access their music anywhere –By streaming their music from the internet It’s the similar story for movies

Solid State Drives (SSD) UsesAdvantages Uses electronically erasable programmable read- only memories (EEPROM) EEPROM allows data to be read or erased in single bytes at a time EEPROM is more useful in certain applications Because of cost implications, majority SSDs use NAND technology More reliable Considerably lighter Don’t have to get ‘up to speed’ before they work Have a lower power consumption Run much cooler than HDDs There are no moving parts, very thin Data access is considerably faster than HDD

Memory Sticks/Pens Drives UsesAdvantagesDisadvantages Transport files between computers or a back up store Security device to prevent software privacy Very compact and portable media Very robust Doesn’t need additional software to work on most computers Not affected by magnetic fields Can’t write-protect the data/files Easy to lose User needs to be very careful when removing the memory stick from a computer

Flash Memory Cards UsesAdvantagesDisadvantages Stores photos on digital cameras Used as mobile phone memory cards Used to store music files Used as a backup store in computer devices Very compact and can be easily removed and used in another device They are very robust Expensive per gigabyte of memory Have a finite life Have a lower storage capacity than hard disks