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What benefits this brings depends on the type of MD device you are creating. Currently supported are: <variablelist> <varlistentry> <term>RAID0</term><listitem><para> Is mainly aimed at performance. RAID0 splits all incoming data into <firstterm>stripes</firstterm> and distributes them equally over each disk in the array. This can increase the speed of read/write operations, but when one of the disks fails, you will lose <emphasis>everything</emphasis> (part of the information is still on the healthy disk(s), the other part <emphasis>was</emphasis> on the failed disk). </para><para> The typical use for RAID0 is a partition for video editing. </para></listitem> </varlistentry> <varlistentry> <term>RAID1</term><listitem><para> Is suitable for setups where reliability is the first concern. It consists of several (usually two) equally-sized partitions where every partition contains exactly the same data. This essentially means three things. First, if one of your disks fails, you still have the data mirrored on the remaining disks. Second, you can use only a fraction of the available capacity (more precisely, it is the size of the smallest partition in the RAID). Third, file-reads are load-balanced among the disks, which can improve performance on a server, such as a file server, that tends to be loaded with more disk reads than writes. </para><para> Optionally you can have a spare disk in the array which will take the place of the failed disk in the case of failure. </para></listitem> </varlistentry> <varlistentry> <term>RAID5</term><listitem><para> Is a good compromise between speed, reliability and data redundancy. RAID5 splits all incoming data into stripes and distributes them equally on all but one disk (similar to RAID0). Unlike RAID0, RAID5 also computes <firstterm>parity</firstterm> information, which gets written on the remaining disk. The parity disk is not static (that would be called RAID4), but is changing periodically, so the parity information is distributed equally on all disks. When one of the disks fails, the missing part of information can be computed from remaining data and its parity. RAID5 must consist of at least three active partitions. Optionally you can have a spare disk in the array which will take the place of the failed disk in the case of failure. </para><para> As you can see, RAID5 has a similar degree of reliability to RAID1 while achieving less redundancy. On the other hand, it might be a bit slower on write operations than RAID0 due to computation of parity information. </para></listitem> </varlistentry> <varlistentry> <term>RAID6</term><listitem><para> Is similar to RAID5 except that it uses two parity devices instead of one. </para><para> A RAID6 array can survive up to two disk failures. </para></listitem> </varlistentry> <varlistentry> <term>RAID10</term><listitem><para> RAID10 combines striping (as in RAID0) and mirroring (as in RAID1). It creates <replaceable>n</replaceable> copies of incoming data and distributes them across the partitions so that none of the copies of the same data are on the same device. The default value of <replaceable>n</replaceable> is 2, but it can be set to something else in expert mode. The number of partitions used must be at least <replaceable>n</replaceable>. RAID10 has different layouts for distributing the copies. The default is near copies. Near copies have all of the copies at about the same offset on all of the disks. Far copies have the copies at different offsets on the disks. Offset copies copy the stripe, not the individual copies. </para><para> RAID10 can be used to achieve reliability and redundancy without the drawback of having to calculate parity. </para></listitem> </varlistentry> </variablelist> To sum it up:
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