Administrator Guide
Table 3. SSD Redundancy Recommendations and Requirements
Drive Size Redundancy Level
Up to 1.7 TB for WI and RI 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.
1.8 TB up to 3.9 TB for WI and RI Dual redundancy is the default when adding drives of this size to
a new or existing page pool.
4 TB and higher for WI and RI Dual redundancy is required when adding drives of this size to a
new or existing page pool.
Data Progression
Storage Center uses Data Progression to move data within a virtualized storage environment. Data Progression moves data between
tiers and drive types, as well as among multiple RAID levels within the same tier, for a constant balance of performance and cost.
How Data Progression Works
Once every 24 hours, Storage Center assesses disk use and moves data to disk space that is more ecient for the data usage. By
default, Data Progression runs each day at 7 PM system time, but the timing of the run can be changed in the Storage Center
settings. Data Progression behavior is determined by the Storage Prole applied to each volume.
NOTE: With SCv2000 series controllers, Data Progression moves data between RAID types and restripes RAID, but does
not move data between storage tiers.
Data Progression and Snapshots
Storage Center also uses Data Progression to move snapshots. When a snapshot is created, either as scheduled or manually, the
data is frozen and moved to the tier specied by the Storage Prole to hold snapshots.
Snapshots can occur as a scheduled event according to the Snapshot Prole, manually by creating a snapshot, or on demand by
Storage Center to move data o of Tier 1 in a Flash Optimized storage type.
Low Space Modes
A Storage Center enters Conservation Mode when free space becomes critically low and enters Emergency Mode when the system
can no longer operate because there is not enough free space.
Conservation Mode
A Storage Center enters Conservation Mode when free space becomes critically low. Immediate action is necessary to avoid entering
Emergency Mode.
NOTE: Because of Conservation Mode’s proximity to the emergency threshold, do not use it as a tool to manage storage
or to plan adding disks to the Storage Center.
In Conservation Mode, Dell Storage Manager Client responds with the following actions:
• Generates a Conservation Mode alert.
• Expires Snapshots at a faster rate than normal.
• Prevents new volume creation.
Storage Center Overview
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