Uniqcli

RAID capacity calculator: usable TB, TiB & spare drives

Compare equal-drive conventional RAID capacity, hot spares and an explicitly unused share.

Storage

RAID usable capacity and drive-count planner

Compare equal-drive conventional RAID capacity, hot spares and an explicitly unused share.

Example inputs · Replace these with your measurements to build your plan.

Method, example and sources
  1. Separate active drives from dedicated hot spares.
  2. Apply the selected conventional layout to equal-capacity active drives.
  3. Remove the entered unused reserve and convert decimal TB to TiB.
  4. Reverse-size the entered target without claiming performance or backup protection.

Worked example. Four equal 8 TB drives in RAID5 provide 24 TB before reserve and formatting. Keeping 20% unused leaves 19.2 TB; the hot-spare count is separate.

Your planning result

Usable capacity for the declared layout

Equal-drive conventional RAID arithmetic; spares and reserve are counted separately.

Raw installed
32TB
Active drives
4
Dedicated spares
0
Usable capacity
24TB
Usable binary capacity
21.8279TiB
Unused reserve
0TB
Minimum total drives for target
4
  • TB means 10^12 bytes; TiB means 2^40 bytes.
  • Formatting, filesystem overhead, mixed-drive policies, rebuild performance and backup are separate.

Compare this capacity with a camera plan →

24 TB is usable capacity after the entered RAID reserve. Recording rates and recorder ingest still need your inputs.

Storage

Screen NAS drive additions and support

Check bays, nominal interface, form factor, workload and entered OEM support without assuming an array migration.

Example inputs · Replace these with your measurements to build your plan.

Method, example and sources
  1. Count free bays before adding the selected number of drives.
  2. Compare declared interface and carrier/form-factor requirements.
  3. Calculate only the new drives' raw capacity and workload allowance.
  4. Record exact NAS, drive, firmware and capacity-variant support before proceeding.

Worked example. Two added 8 TB drives contribute 16 TB of raw capacity. This does not say how much a running array can expand or whether its firmware supports the drives.

Planning result · confirm model details

Separate physical screening from OEM support

Added capacity is raw; existing drive capacities and array expansion behavior have not been assumed.

Bays remaining after addition
0
Added raw capacity
16TB
Added raw binary capacity
14.5519TiB
Workload allowance remaining
120TB/year
Screen NAS drive additions and support: detailed result
CheckEntered result
Available baysWithin / documented
Same entered interfaceWithin / documented
Same entered form factorWithin / documented
Entered workload allowanceWithin / documented
Exact supported configurationReview required
  • Not listed is not proven incompatible. A matching interface/form factor does not establish NAS firmware support.
  • SAS controllers, carriers/adapters, sector format, CMR/SMR policy, workload limits and array migration require exact model evidence. Use the RAID tool separately for usable capacity.

From the catalog

Hard Drives/Solid State Drives

Explore related listings, then confirm the exact model requirements against your plan. These listings are not an automatic compatibility or capacity verdict.

Browse hard drives/solid state drives Browse storage arrays & servers Get help with the specification

Capacity begins with the layout

Start with the capacity of one actual drive and the number of physical drives you will install. Dedicated hot spares remain installed but do not add online capacity. This worksheet models conventional equal-drive RAID, including an even mirrored-pair count for RAID10; it does not reproduce every enclosure vendor's expansion or mixed-drive policy.

Keep reserve and protection separate

The unused share is removed from the capacity available after the selected layout. It is not another parity drive. Decimal TB and binary TiB describe the same bytes with different units. Filesystem metadata, snapshots and application reserve can reduce capacity further. A calculated capacity does not establish controller support, rebuild behavior, performance or recoverability; keep a separate backup plan.

Worked example

Four equal 8 TB drives in RAID5 provide 24 TB before reserve and formatting. Keeping 20% unused leaves 19.2 TB; the hot-spare count is separate.

Physical screening is only the first step

Begin with the number of actually usable bays and those already occupied. Compare the enclosure and drive interface and physical carrier requirements, then consider the workload rating of the exact drive. A nominal mismatch is a review item, not a universal compatibility rule: an OEM may document a supported controller or carrier arrangement that requires more specific evidence.

Preserve the support-list distinction

A drive absent from a support list is not automatically proven incompatible. Exact firmware, capacity variant, sector format and enclosure policy matter, and some configurations have vendor support limits beyond physical fit. The additional capacity shown is raw; existing drive sizes and array migration were not assumed. Use a separate layout calculation and a tested backup plan before changing a populated system.

Worked example

Two added 8 TB drives contribute 16 TB of raw capacity. This does not say how much a running array can expand or whether its firmware supports the drives.

RAID capacity calculator: usable TB, TiB & spare drives — Uniqcli