Understanding RAID groups

About RAID groups in Data ONTAP

A RAID group consists of a set of at least one data disk and one parity disk. Data disks contain data from clients. Data ONTAP uses the parity disk if there is a disk failure to reconstruct the failed disk's data in conjunction with the other data disks. Data ONTAP assigns the role of parity disk to the largest disk in the RAID group.

Each RAID group belongs to only one volume (physical file system); you cannot assign a RAID group to more than one volume.

Data ONTAP enables you to have up to 150 RAID groups per filer or cluster.

How Data ONTAP creates RAID groups automatically

Data ONTAP automatically assigns hot spare disks to RAID groups. A hot spare disk is a disk in a disk shelf that does not yet hold data and is ready for use.

Data ONTAP creates new RAID groups as each RAID group is filled with its maximum number of disks. Hot spare disks do not have to be in the same disk shelf as other disks of a RAID group to be available to a RAID group.