RAID0

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Revision as of 15:44, 4 September 2007

RAID level 0, typically shortened to RAID0 and often referred to as disk striping, is a method by which two or more physical disks masquerade as one single larger disk.

Advantages

Speed

Speed is often a factor in choosing this RAID level due to the performance of data reads and writes, as in the following example:

Four disks are used to create a single RAID0 drive using a software RAID driver A user application saves a 1MiB file to this drive. The RAID0 driver splits the file into four separate 256KiB elements and writes one of them to each physical disk at the same time. Theoretically the system can write files four times faster using this method then it would to a single disk. Reading data is done in the opposite way where four individual disk reads are made and the file re-assembled from the four elements before being passed onto the user application.

Note that RAID0 is not restricted to four disks as in the above example, any number from two to the maximum the system will handle will operate under RAID0.

Space

Space is another advantage since all disks in the RAID can be utilized to store data.

Cost

The implementation of this RAID level can be achieved in software there-by reducing the need to purchase dedicated hardware RAID controllers.

Disadvantages

Reliability

The main disadvantage of this RAID level is the lack of fault tolerance. Since data is split up and written across all disks a failure of one drive will cause the total loss of all data within the RAID.

Variations

There are a number of variations that can be applied to this RAID level. The two common ones are:

JBOD

JBOD, which is simply Just a Bunch Of Disks is a method that operates like RAID level 0 but does not have the requirement of the disks having the same capacity, hence the name. It offers the same advantages and disadvantages on RAID0.

RAID 10

RAID10, sometimes referred to as RAID level 01, level 0+1, level 1+1, mirrored striping, gives the advantages of RAID0 but with the redundancy and data safe-guarding of RAID1 thereby limited the disadvantages of RAID0.

This RAID level achieves this by creating two identical RAID0 disks and then applies RAID1, or mirroring, over the top of them. This means that if one of the underlying disks in one of the RAID0 sets fails the other RAID0 will retain system and data reliability. However if one disk from both RAID0 sets fails all data will be lost.

Uses

Typical usage for this RAID level is in the field of audio and/or video editing or indeed anything that requires rapid data reading and writing without the need to safeguard data loss.

Support

FreeBSD supports software based RAID0 through the GEOM disk management subsystem.

Warning

IT MUST BE STRESSED THAT RAID LEVEL 0 / DISK STRIPING (AND THE JBOD VARIATION) SHOULD NOT BE USED IN PRODUCTION ENVIRONMENTS WHERE DATA INTEGRITY AND RELIABILITY MUST BE ASSURED. This RAID level should only be used where non-essential data needs reading or writing to disk quickly.

@@ Line 1: / Line 1: @@
-[[RAID0]] is striping across multiple physical disks without any parity - this means that, while you are gaining something in terms of read and write speed, and your total volume space is the sum of the space on your individual providers (drives), any single point failure will irretrievably destroy ALL data in that array.
+RAID level 0, typically shortened to RAID0 and often referred to as disk striping, is a method by which two or more physical disks masquerade as one single larger disk.
-FreeBSD does support [[geom]] RAID0 striping, should you wish to indulge yourself in it, but unless you're setting up a more complex multi-stage array - for example, a RAID0 striping of RAID1 mirrored providers - it is HIGHLY RECOMMENDED that you do not use this RAID type.
+== Advantages ==
+=== Speed ===
+Speed is often a factor in choosing this RAID level due to the performance of data reads and writes, as in the following example:
+''Four disks are used to create a single RAID0 drive using a software RAID driver  A user application saves a 1MiB file to this drive.  The RAID0 driver splits the file into four separate 256KiB elements and writes one of them to each physical disk at the same time.  Theoretically the system can write files four times faster using this method then it would to a single disk.  Reading data is done in the opposite way where four individual disk reads are made and the file re-assembled from the four elements before being passed onto the user application.''
+Note that RAID0 is not restricted to four disks as in the above example, any number from two to the maximum the system will handle will operate under RAID0.
+=== Space ===
+Space is another advantage since all disks in the RAID can be utilized to store data.
+=== Cost ===
+The implementation of this RAID level can be achieved in software there-by reducing the need to purchase dedicated hardware RAID controllers.
+== Disadvantages ==
+=== Reliability ===
+The main disadvantage of this RAID level is the lack of fault tolerance.  Since data is split up and written across all disks a failure of one drive will cause the total loss of all data within the RAID.
+== Variations ==
+There are a number of variations that can be applied to this RAID level.  The two common ones are:
+=== JBOD ===
+JBOD, which is simply ''Just a Bunch Of Disks'' is a method that operates like RAID level 0 but does not have the requirement of the disks having the same capacity, hence the name.  It offers the same advantages and disadvantages on RAID0.
+=== RAID 10 ===
+RAID10, sometimes referred to as RAID level 01, level 0+1, level 1+1, mirrored striping, gives the advantages of RAID0 but with the redundancy and data safe-guarding of RAID1 thereby limited the disadvantages of RAID0.
+This RAID level achieves this by creating two identical RAID0 disks and then applies RAID1, or mirroring, over the top of them.  This means that if one of the underlying disks in one of the RAID0 sets fails the other RAID0 will retain system and data reliability.  However if one disk from both RAID0 sets fails all data will be lost.
+== Uses ==
+Typical usage for this RAID level is in the field of audio and/or video editing or indeed anything that requires rapid data reading and writing without the need to safeguard data loss.
+== Support ==
+FreeBSD supports software based RAID0 through the GEOM disk management subsystem.
+== Warning ==
+IT MUST BE STRESSED THAT RAID LEVEL 0 / DISK STRIPING (AND THE JBOD VARIATION) SHOULD NOT BE USED IN PRODUCTION ENVIRONMENTS WHERE DATA INTEGRITY AND RELIABILITY MUST BE ASSURED.  This RAID level should only be used where non-essential data needs reading or writing to disk quickly.
 [[Category:FreeBSD Terminology]]
 [[Category:RAID]]