RAID Management
RAID helps to divide data storage over multiple disks, providing increased data reliability. For FortiAnalyzer devices containing multiple hard disks, you can configure the RAID array for capacity, performance, and/or availability.
Supported RAID levels
FortiAnalyzer units with multiple hard drives can support the following RAID levels:
Linear RAID
A Linear RAID array combines all hard disks into one large virtual disk. The total space available in this option is the capacity of all disks used. There is very little performance change when using this RAID format. If any of the drives fails, the entire set of drives is unusable until the faulty drive is replaced. All data will be lost.
RAID 0
A RAID 0 array is also referred to as striping. The FortiAnalyzer unit writes information evenly across all hard disks. The total space available is that of all the disks in the RAID array. There is no redundancy available. If any single drive fails, the data on that drive cannot be recovered. This RAID level is beneficial because it provides better performance, since the FortiAnalyzer unit can distribute disk writing across multiple disks. l Minimum number of drives: 2
RAID 1
A RAID 1 array is also referred to as mirroring. The FortiAnalyzer unit writes information to one hard disk, and writes a copy (a mirror image) of all information to all other hard disks. The total disk space available is that of only one hard disk, as the others are solely used for mirroring. This provides redundant data storage with no single point of failure. Should any of the hard disks fail, there are backup hard disks available.
- Minimum number of drives: 2
- Data protection: Single-drive failure
One write or two reads are possible per mirrored pair. RAID 1 offers redundancy of data. A rebuild is not required in the event of a drive failure. This is the simplest RAID storage design with the highest disk overhead.
RAID 1s
A RAID 1 with hot spare array uses one of the hard disks as a hot spare (a stand-by disk for the RAID). If a hard disk fails, within a minute of the failure the hot spare is substituted for the failed drive, integrating it into the RAID array and rebuilding the RAID’s data. When you replace the failed hard disk, the new hard disk is used as the new hot spare. The total disk space available is the total number of disks minus two.
RAID 5
A RAID 5 array employs striping with a parity check. Similar to RAID 0, the FortiAnalyzer unit writes information evenly across all drives but additional parity blocks are written on the same stripes. The parity block is staggered for each stripe. The total disk space is the total number of disks in the array, minus one disk for parity storage. For example, with four hard disks, the total capacity available is actually the total for three hard disks. RAID 5 performance is typically better with reading than with writing, although performance is degraded when one disk has failed or is missing. With RAID 5, one disk can fail without the loss of data. If a drive fails, it can be replaced and the FortiAnalyzer unit will restore the data on the new disk by using reference information from the parity volume.
- Minimum number of drives: 3
- Data protection: Single-drive failure
RAID 5s
A RAID 5 with hot spare array uses one of the hard disks as a hot spare (a stand-by disk for the RAID). If a hard disk fails, within a minute of the failure, the hot spare is substituted for the failed drive, integrating it into the RAID array, and rebuilding the RAID’s data. When you replace the failed hard disk, the new hard disk is used as the new hot spare. The total disk space available is the total number of disks minus two.
RAID 6
A RAID 6 array is the same as a RAID 5 array with an additional parity block. It uses block-level striping with two parity blocks distributed across all member disks.
l Minimum number of drives: 4 l Data protection: Up to two disk failures.
RAID 6s
A RAID 6 with hot spare array is the same as a RAID 5 with hot spare array with an additional parity block.
RAID 10
RAID 10 (or 1+0), includes nested RAID levels 1 and 0, or a stripe (RAID 0) of mirrors (RAID 1). The total disk space available is the total number of disks in the array (a minimum of 4) divided by 2, for example:
- 2 RAID 1 arrays of two disks each, l 3 RAID 1 arrays of two disks each, l 6 RAID1 arrays of two disks each.
One drive from a RAID 1 array can fail without the loss of data; however, should the other drive in the RAID 1 array fail, all data will be lost. In this situation, it is important to replace a failed drive as quickly as possible.
- Minimum number of drives: 4 l Data protection: Up to two disk failures in each sub-array.
RAID 50
RAID 50 (or 5+0) includes nested RAID levels 5 and 0, or a stripe (RAID 0) and stripe with parity (RAID 5). The total disk space available is the total number of disks minus the number of RAID 5 sub-arrays. RAID 50 provides increased performance and also ensures no data loss for the same reasons as RAID 5. One drive in each RAID 5 array can fail without the loss of data.
- Minimum number of drives: 6
RAID 60
A RAID 60 (6+ 0) array combines the straight, block-level striping of RAID 0 with the distributed double parity of RAID 6.
- Minimum number of drives: 8 l Data protection: Up to two disk failures in each sub-array.