RAID Concept:
RAID stands for Redundant Array of Independent Disk.
Basic information that is needed for DBA is covered in this
topic. For more information please refer the below link.
RAID Levels:
RAID 0:
STRIPING of data is allowed across multiple disks. Input
Output rate is increased (IOPS) due to striping. Placing LDF on this type of
disk will not fetch good performance as it is sequential write. Disaster
Recovery is not possible when any one of the disk fails.
RAID 1:
MIRRORING of data is allowed across multiple disks. WRITE
operation takes more time comparatively to READ operation. FAULT tolerance is
provided as data is mirrored between disk. Read performance will be very good.
Disaster Recovery is possible.
RAID 5:
STRIPING WITH PARITY is allowed across multiple disk. Parity
information is required to recover the data at time of disaster recovery.
Minimum disk required are 3 and parity information is shared in them. If 3 disks
are configured then data disk storage size is 2 disks. Data size is (n-1). N is
size of each disk. Write performance will be very poor as parity calculation
takes time.
RAID 6:
STRIPING WITH PARITY is allowed across multiple disk. Parity
information is required to recover the data at time of disaster recovery.
Minimum disk required are 4 and parity information is shared in them. If 4 disks
are configured then data disk storage size is 2 disks. Data size is (n-2). N is
size of each disk. Write performance will be very poor as parity calculation
takes time. In Write performance RAID 5 is better than
RAID 6.
RAID 10:
Known as STRIPED PAIR OF MIRRORS. RAID 10 is combination of
RAID (1 + 0). Number of disk required for this RAID level should be in even
number, atleast 4 disks are required. Disks are grouped in pairs. RAID 1 (Mirroring) is applied on pairs of
Disks and RAID 0 (Striped) is applied set of pairs.
RAID 01:
Known as MIRRORED PAIR OF STRIPED. RAID 01 is combination of
RAID (0 + 1). Number of disk required for this RAID level should be in even
number, atleast 4 disks are required. Disks are grouped in pairs. RAID 0 (Striped) is applied on pairs of
Disks and RAID 1 (Mirroring) is applied set of pairs.
