**R**edundant **A**rray of **I**ndependent **D**isks
**R**edundant **A**rray of **I**ndependent **D**isks
## Some recorrent terms when defining a RAID system:
## Some recorrent terms when defining a RAID system:
**PARITY**
**PARITY**
: Refers to *parity bit*, it's a bit added to a string that says if the sum of bits in the string is even/odd, it's a simple form of error checking. Commonly the parity bit is added in the end of each byte (8 bits).
: Refers to *parity bit*, it's a bit added to a string that says if the sum of bits in the string is even/odd, it's a simple form of error checking. Commonly the parity bit is added in the end of each byte (8 bits).
**DATA STRIPING**
: The concept of dividing each data array into various segments so the data can be more easily manipulated and stored
**MIRROR**
: Replicates *logical disk* volumes into multiple fisical disks, so the same information is stored in different hard disks in real time
## RAID0
## RAID0
>RAID0 splits data across a multiple-disks array. The ideal setup is equaly-sized disks since the total storage used in a RAID0 arrangement is equal to the lower storage disk space times the total amount of disks. I a array of one 120Gb disk and one 360Gb disk, the total storage available would be 240 Gb.
RAID0 splits data across a multiple-disks array. The ideal setup is equaly-sized disks since the total storage used in a RAID0 arrangement is equal to the lower storage disk space times the total amount of disks. I a array of one 120Gb disk and one 360Gb disk, the total storage available would be 240 Gb.
>
>RAID0 create stripes of data so disk operations are n-times faster, n being the total amount of disks available. It also distributes I/O costs between all disks making it a very fast storage system. RAID0 **doesn't implements parity** or even any **fault tolerance**, so the failure of one single disk in the array will result in total data loss.
RAID0 create stripes of data so disk operations are n-times faster, n being the total amount of disks available. It also distributes I/O costs between all disks making it a very fast storage system. RAID0 **doesn't implements parity** or even any **fault tolerance**, so the failure of one single disk in the array will result in total data loss.
>
>Besides fastness, RAID0 also is a good system to create large amounts of data storage units with lesser disks, since all disks in the array have unique information and, having equaly-sized units, uses 100% it's fisical capability as storage.
Besides fastness, RAID0 also is a good system to create large amounts of data storage units with lesser disks, since all disks in the array have unique information and, having equaly-sized units, uses 100% it's fisical capability as storage.
## RAID1
## RAID1
RAID1 mirrors sets of data on **two or more** fisical disks at a time. This RAID setting, as in RAID0, also doesn't offer any *parity* and the setup replicates the size of the smallest disk on all the other disks as well. In RAID1 theres no data striping since all data is replicated multiple times.
RAID1 read operations can be taken by any of the disks in the array, it's useful on read performance and reliability on data, but it is bad on write performance and total data storage capacity.
