Release Notes

Storage configuration
12 Dell EMC SC Series: Performance and Availability | 4024-BP-SC
The disk tier redundancy should be chosen prior to setting up the SC Series system. If you need help
determining which type best suits a particular need, contact your Dell EMC storage specialist or business
partner. Note that larger drives will default to dual redundancy by the system, and in some case may be
forced to use dual redundancy.
2.4 Dual redundancy requirements
Dual redundancy in a tier allows for a dual drive failure within that tier without data loss. Redundancy
requirements for each tier are based on the size of the disk drive in the tier, and whether the disks are added
to an existing disk folder or a new disk folder. During installation, the desired redundancy level can be
selected. Dual redundancy for larger HDD drives will be required. The requirements and recommendations for
dual redundancy are shown in Table 1.
Dual redundancy requirements based on capacity
Disk type
Recommended capacity
New storage type
(required)
Existing storage type
(required)
HDD
966 GB to 2.4 TB
2.5 TB or larger
2.79 TB or larger
SSD
1.7 TB or larger
N/A
4.0 TB or larger
For new SC Series array installations, HDD disks of 2.5 TB and above must use a dual redundant RAID level
(RAID 10 DM or RAID 6). For existing arrays with 2.79 TB or larger HDDs or 4.0 TB SSD disks, dual
redundancy is also required.
Note: For SSDs, these rules may change over time as technology advances. These rules apply to SCOS 7.3
at the current publication date. Refer to the release notes for the appropriate SCOS version.
2.5 Storage profiles
SC Series arrays use storage profiles to determine which tier and RAID type that volume data is written to.
The storage profile also defines where data will exist after a snapshot is taken and as it ages. Generally, the
default storage profile is recommended for volumes. However, there are reasons to use the other available
storage profiles, or even create a custom storage profile for volumes that are to be handled differently.
Example: For a volume that needs to remain in tier 1 storage for performance reasons, you can use the
High priority profile. This profile keeps all volume data in tier 1. New writes will go to mirror RAID and frozen
data contained in a snapshot will be progressed to parity RAID.
2.6 All-flash array
All-flash arrays provide the highest level of performance in the SC Series family. Use an all-flash array when
the application requires the highest storage performance at the lowest response time. Dell EMC recommends
disabling write cache for any volumes that will always be writing data directly into a flash tier. If the flash tier
becomes full and writes are redirected to an HDD tier, there will be a performance reduction on those
volumes, and in that case, write cache should be enabled on the volume.
Deduplication is only supported on SC Series systems with a minimum number of flash drives attached (see
the release notes for the appropriate SCOS release).
Dell EMC recommends that all drives of a similar type be of the same size.