Can one recover data from a failed drive in RAID 0 array?

RAID stands for redundant array of independent disks. There are various RAID implementations, some built for boosting the performance, some for increasing the redundancy of the data and some others for achieving both. RAID 0 is built solely for performance boosting. In RAID 0, the data is split in to stripes and is stored independently on different drives. The data is read or transferred parallely and this increases the speed of RAID 0 system. Basically, for such a system, redundancy or fail safe is zero or does not exist. In RAID 0, error checking is not implemented. So, one cannot check for errors in his data in a RAID 0 system.
More number of drives increases the speed with which one can access or write data incredibly. But if even one drive fails in a RAID 0 system, the entire information stored on all the three drives is lost because the data is stored in divided blocks. To put it simply, if you are storing a movie file on a RAID 0 system, some part of the movie is stored on drive one, some of it is stored on other drive and remaining part on remaining drives. So, even if one drive fails, one part of your movie is destroyed. And as a result, the integrity of your movie file is disrupted. So, you cannot play the file.
RAID 0 implementation is used in gaming servers where there is no need for a failsafe, but the only need is higher speed. If you notice that one hard drive among your RAID 0 system is failing, you should immediately back up the drive, or remove the drive from RAID 0 system by copying the data on that drives to other drives of RAID 0 system. In this way, one can protect their data from a hard disk failure. In case of a failed hard drive in a RAID 0 system, it is not impossible to recover the data but it is not even easy. The data from the failed hard drive disks can be collected by specialized professionals and some softwares. Then that data can be added to the existing RAID 0 system.
There are other RAID implementations like RAID 1, 2, 3 and so on till 6. Some of these are built strictly for data security such as RAID 1. This implementation needs at least two identical hard drives. RAID 1 mirrors the data stored on one drive on to the other, so that in case of failure, a back-up is immediately available.

By: Sandeep Mahanthi

4 mm DAT tape drives and their use in back up devices:

A tape drive is relatively an older generation of storage technologies. DAT stands for Digital Audio Tape. The storage of digital data on these tapes gives rise to a computer data storage format known as DDS which means Digital Data Storage. Several versions of DDS were developed and some of these versions are still in use in the present day modern backup technology. 4 mm DAT drives and other DAT drives were used under DDS specification in a robust cockpit voice and flight data recorders as a black box for the flights, jets and aeroplanes. These are also used is several other applications where data storage with other technologies becomes unreliable.
A DDS tape drive uses helical scanning for recording the data. This is the same process that is used by VCR recorders. If any errors are found in the data stored, the write head rewrites the data. DDS generally uses a 3.8 mm wide tape drive for recording the data. However, in the newer versions of DDS, the tape width has been extended up to as much as 8 mm wide. Tape drives are sensitive to various physical conditions like dust and moisture. So, these tape drives must be cleaned regularly for efficient performance. Otherwise, the data stored might be at risk due to the physical destruction caused to the drive. Companies such as Seagate, HP and others manufacture these tape drives for back up storage purposes.
There are various generations of DDS specifications. Let us have a look at them.
DDS-1: This was the first generation of DDS and it is most commonly known as just DDS. This technology offered 1.3 GB of uncompressed data storage with a 60 meter long tape drive. When the data is compressed, the data stored can be doubled, that is 2.6 GB of compressed data. More data capacity can be achieved by using more length of tape.
DDS-2: This offered 4 GB uncompressed and 8 GB compressed data on a 120 meter long tape drive.
DDS-3: 12 GB uncompressed and 24 GB compressed data on 125 m drive. DDS 3 also uses advanced technology that minimises the electric noise and helps for cleaner data recording.
DDS-4 20 GB uncompressed and 40 GB compressed data on 150 m drive. Also known as DAT 40.
DAT 72: It was developed by HP and Certance. It offers 36 GB uncompressed with 72 GB compressed amount of data storage.
DAT 160 and DAT 320 are other generations which offered 80 GB and 160 GB of uncompressed data respectively. When compressed, double the amount of data can be stored. These latest devices have host interfaces for connecting through SCSI, USB and other standards.

By: Sandeep Mahanthi

Secure Digital Card or SD card

Secure Digital card or SD card is a flash memory card that provides storage for portable various electronic devices like eBooks, digital cameras, PDAs, audio players, video recorders and mobile phones music players, camcorders and personal computers. SD cards are small in size, weighs approximately two grams and robust and have higher data transfer rates and low power consumption of primary energy, and mobile devices. It uses flash memory to provide non-volatile storage, which means that power is not necessary to retain stored data.
Secure Digital card is the size of postage stamp  It 'the same size as the MMC, but smaller than previous memory card types including Smart Media cards elderly and Compact Flash cards. Both MMC and SD cards can be encryption capabilities for protected content to ensure the secure distribution of copyrighted material, such as digital music, videos and books. SD cards are available with storage capacities up to 4 gigabytes.
Both MMC and SD card use metal connector contacts instead of the traditional pins and connectors, are therefore not subject to damage during handling