Supported RAID Configurations
RAID is short for Redundant Array of Independent (or Inexpensive) Disks, which is a category of storage that employs two or more drives in combination for fault tolerance and performance.
DXi6900 G1 and G2 systems use the following RAID levels:
DXi6900-S systems use the following RAID levels:
RAID 1 Configuration
RAID 1 provides redundancy and fault tolerance by mirroring disks. Each disk in the RAID set contains a copy of the same data. For example, in a RAID set with two disks, if one disk fails, all of the data still exists on the other disk.
The DXi6900 G1 and G2 Nodes use RAID 1 sets for the boot disk (operating system) as well as for the blookpool index.
The Node contains the following RAID 1 sets (see Figure 1):
- BOOT - HDD slots 1 and 8 (operating system and journal files)
- META 1 - HDD slots 2 and 9 (blockpool index)
- META 2 - HDD slots 3 and 10 (blockpool index)
- META 3 - HDD slots 4 and 11 (blockpool index)
- META 4 - HDD slots 5 and 12 (blockpool index)
- META 5 - HDD slots 6 and 13 (blockpool index)
- META 6 - HDD slots 7 and 14 (blockpool index)
Note: Node HDD slots 0 and 15 contain global hot spares.
Figure 1: DXi6900 Node RAID Sets
| 1 - HDD Slot 0 (Spare) | 5 - HDD Slot 4 (META 3) | 9 - HDD Slot 8 (BOOT) | 13 - HDD Slot 12 (META 4) |
| 2 - HDD Slot 1 (BOOT) | 6 - HDD Slot 5 (META 4) | 10 - HDD Slot 9 (META 1) | 14 - HDD Slot 13 (META 5) |
| 3 - HDD Slot 2 (META 1) | 7 - HDD Slot 6 (META 5) | 11 - HDD Slot 10 (META 2) | 15 - HDD Slot 14 (META 6) |
| 4 - HDD Slot 3 (META 2) | 8 - HDD Slot 7 (META 6) | 12 - HDD Slot 11 (META 3) | 16 - HDD Slot 15 (Spare) |
RAID 6 Configuration
RAID 6 uses block-level striping with two parity blocks distributed across all member disks. Dual parity provided by a RAID 6 configuration ensures that your data retains full integrity even in the event of two hard drive failures. .
The DXi6900-S uses RAID 6 volumes for data storage (see Figure 2).
Figure 2: DXi6900-S Node RAID Sets
| 1 - SDD Slot 0 | 5 - SDD Slot 4 | 9 - SDD Slot 8 | 13 - SDD Slot 12 |
| 2 - SDD Slot 1 | 6 - SDD Slot 5 | 10 - SDD Slot 9 | |
| 3 - SDD Slot 2 | 7 - SDD Slot 6 | 11 - SDD Slot 10 | |
| 4 - SDD Slot 3 | 8 - SDD Slot 7 | 12 - SDD Slot 11 |
Dynamic Disk Pool (DDP) Technology
Dynamic Disk Pool (DDP) technology is a new alternative to traditional RAID configuration. DDP distributes data, parity information, and spare capacity across a pool of drives, providing the following benefits:
- Faster drive recovery
- Easier storage expansion
- Dynamic re-balancing of data across drives
- Better data availability
The DXi6900 Array modules (RBODs) and Expansion modules (EBODs) use Dynamic Disk Pool technology for data storage (see Figure 3). All hard disk drives in an Array or Expansion module are configured in a single DDP pool.
The Dynamic Disk Pool does not include a physical hot spare. However, enough disk space is reserved to provide the equivalent of a hot spare. And similar to RAID 6, a DDP pool can tolerate up to two drive faults.
Figure 3: DXi6900 Array and Expansion Module DDP Pools
| 1 - DDP Pool | 4 - DDP Pool | 7 - DDP Pool | 10 - DDP Pool |
| 2 - DDP Pool | 5 - DDP Pool | 8 - DDP Pool | 11 - DDP Pool |
| 3 - DDP Pool | 6 - DDP Pool | 9 - DDP Pool | 12 - DDP Pool |
