Release Notes

SC Series features
15 Dell EMC SC Series: Performance and Availability | 4024-BP-SC
addition, the included Volume Advisor helps automate the process. The combination of this feature and the
Volume Advisor allows data to move freely and transparently across local, campus, metro, or geographically
dispersed distances, without interrupting workloads or reconfiguring hosts.
Live Volume lets you perform maintenance on an active system without affecting production workloads,
replicating new writes automatically as you go, and swapping primary paths manually as needed, or
automatically. You can also take impromptu disaster-avoidance precautions to quickly prepare for potential
outages, such as hurricanes, without predefined disaster recovery mappings.
3.4 Snapshots
Snapshots allow the creation of local recovery points for any volume or group of volumes. These snapshots
do not take any additional space, but freeze the pages of a volume as read only. Any new writes or updates to
frozen pages will take up additional space because the frozen pages cannot be modified. These snapshots
can be automatically expired after a user-selected time period has passed.
Snapshots may increase the overall bandwidth needed on the SAS backend, which is due to the backfilling of
the frozen data when updates are made to a frozen page. Consider the overhead of snapshots when planning
both performance and capacity requirements for the storage system.
Dell EMC recommends the practice of staggering volume snapshot operations (such as creation or deletion),
to minimize the bandwidth load on the SAS backend. This can be accomplished by using different snapshot
schedules for different sets of volumes.
Snapshots are deleted by the system asynchronously; when a snapshot is in the process of being deleted, it
is marked as expired. The system then coalesces the pages into the unexpired snapshot to ensure that any
unexpired snapshot can be recovered.
3.5 Deduplication and Compression
SC Series compression is available with SCOS 7.0 or later.
Supported SC Series volumes have the option to be compressed, or deduplicated and compressed. Data
reduction is not supported on the SCv20x0 models, and SCv30x0 models only have compression available.
The data reduction process is executed during On-Demand Data Progression (initiated by a snapshot) or
during the daily Data Progression cycle. The data reduction process is run by the system and may have an
overall effect on available resources.
An individual volume’s data not contained in a snapshot will not be compressed; the compression works on
the snapshot data only and may impact the snapshot access (accessible frozen pages).
Data reduction occurs on the lowest tier of the media type (lowest tier of flash or spinning disk).
Rules for deduplication and compression (for systems with flash) include the following:
• Tier 1 only (flash): Deduplication and compression
• Tier 1 flash, tier 3 HDD: Deduplication and compression on both tiers
• Tier 1 write-intensive flash, tier 2 read-intensive flash: Deduplication and compression on tier 2 only
• Tier 1 write-intensive flash, tier 2 read-intensive flash, tier 3 HDD: Deduplication and compression on
tier 2 and tier 3 only
• Tier 1 flash, tier 2 HDD, tier 3 HDD: Deduplication and compression on tier 1 and tier 3 only