Administrator Guide
Redundancy
Redundancy levels provide fault tolerance for a drive failure.
• Non-redundant: Uses RAID 0 in all classes, in all tiers. Data is striped but provides no redundancy. If one drive fails, all data is lost.
Do not use non-redundant storage for a volume unless the data has been backed up elsewhere.
• Single-redundant: Protects against the loss of any one drive. Single-redundant tiers can contain any of the following types of
RAID storage.
– RAID 10 (each drive is mirrored)
– RAID 5-5 (striped across 5 drives)
– RAID 5-9 (striped across 9 drives)
• Dual-redundant: Protects against the loss of any two drives. Dual-redundant tiers can contain any of the following types of RAID
storage.
– RAID 10 Dual-Mirror (data is written simultaneously to three separate drives)
– RAID 6-6 (4 data segments, 2 parity segments for each stripe)
– RAID 6-10 (8 data segments, 2 parity segments for each stripe)
Redundancy options may be restricted depending on the drive size. For example, there may be instances when a tier must be dual-
redundant and cannot be non-redundant or single-redundant. These restrictions are described in Redundancy Level
Recommendations and Requirements
Redundancy Level Recommendations and Requirements
Drive size is used to determine the redundancy level to apply to a tier of drives.
If any drive in a tier surpasses a threshold size, a specic redundancy level can be applied to the tier containing that drive. The
following tables describe HDD and SSD redundancy level defaults and requirements for Storage Center 7.1. If a redundancy level is
required, theStorage Center operating system sets the level and it cannot be changed.
NOTE: Dual redundancy is the default redundancy level for all drives in SCv3000 series, SC7020, SC7020F, SC5020, and
SC5020F storage systems. Single redundancy is the default redundancy level for other models of Storage Centers.
Table 2. HDD Redundancy Recommendations and Requirements
Drive Size Redundancy Level
Up to 966 GB For most models of Storage Centers, single redundancy is the
default when adding drives of this size to a new or existing page
pool.
NOTE: For drives of this size, dual-redundant the default
redundancy level for SCv3000 series, SC7020,
SC7020F, SC5020, and SC5020F storage systems.
967 GB up to a maximum 1.93 TB Dual redundancy is the default when adding drives of this size to
a new or existing page pool.
1.94 TB and higher Dual redundancy is required when adding drives of this size to a
new page pool.
NOTE: For SCv3000 series, SC7020, SC7020F, SC5020,
and SC5020F storage systems, dual redundancy is
required when adding drives of this size to new or
existing page pools.
2.79 TB and higher Dual redundancy is required when adding drives of this size to an
existing page pool.
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Storage Center Overview