How to Use the UGREEN NAS RAID Calculator
Use the UGREEN NAS RAID Calculator by selecting HDD or SSD, adding each planned drive, and choosing Basic, JBOD, RAID 0, RAID 1, RAID 5, RAID 6, or RAID 10. The calculator then estimates available capacity, protection, system-reserved space, unused space, and compatible UGREEN NAS models.
How Do You Use the UGREEN RAID Calculator?
Follow these steps before purchasing drives or creating a new storage pool:
- Open the UGREEN NAS RAID Calculator.
- Select HDD or SSD. The toggle displays the appropriate drive-capacity options and identifies the media type for storage planning and compatibility. It does not change the RAID capacity formula itself.
- Add the capacity of each drive that will participate in the storage pool. For example, select 8TB four times when planning a pool with four 8TB HDDs.
- Select Basic, JBOD, RAID 0, RAID 1, RAID 5, RAID 6, or RAID 10.
- Review the available capacity, protection, reserved system space, and unused space.
- Check the recommended UGREEN NAS models and confirm that the exact drives appear on the UGREEN NAS compatibility list.
Changing the RAID type lets you compare how the same drives behave under different configurations. This is particularly useful when deciding whether greater usable capacity or additional drive-failure tolerance matters more.
What Do the RAID Calculator Results Mean?
UGREEN NAS RAID calculator divides your installed storage into several categories.
| Calculator result | What it means |
|---|---|
| Available capacity | Estimated space available for data after the selected RAID layout and system reservation |
| Protection | Capacity allocated to mirroring or parity so the RAID can tolerate specified drive failures |
| Reserved for system | Space required for UGOS Pro system partitioning |
| Unused space | Drive capacity that cannot participate in the selected configuration, usually because the drives have different capacities |
Protection capacity is part of the RAID layout. It is not a second copy of your files that can be browsed or used as an independent backup.
Why Is Available NAS Capacity Lower Than Raw Capacity?
Raw capacity is the total advertised capacity of every installed drive. Available capacity is lower because of RAID protection, storage-unit conversion, system partitioning, file-system metadata, and—in some configurations—unused capacity on larger drives.
RAID Mirroring and Parity Use Capacity
Let N represent the number of participating drives and S represent the capacity of the smallest participating drive.
| Storage mode | Minimum drives | Decimal data-capacity rule |
|---|---|---|
| Basic | 1 | Capacity of the selected drive |
| JBOD | 1 | Sum of participating drive capacities |
| RAID 0 | 2 | N × S |
| RAID 1 | 2 | S |
| RAID 5 | 3 | (N − 1) × S |
| RAID 6 | 4 | (N − 2) × S |
| RAID 10 | 4, even number | (N ÷ 2) × S |
These formulas calculate decimal data capacity before system and file-system overhead. For a complete explanation of each configuration, see What Is RAID? UGREEN NAS RAID Types Explained.
Drive Manufacturers and Operating Systems Use Different Units
Drive manufacturers define 1TB as 1,000,000,000,000 bytes. Operating systems commonly calculate capacity using binary units, where 1TiB equals 1,099,511,627,776 bytes.
As a result:
- An advertised 8TB drive contains approximately 7.28TiB.
- An advertised 16TB drive contains approximately 14.55TiB.
- An advertised 24TB RAID data capacity converts to approximately 21.83TiB.
This unit conversion is one of the main reasons a newly created storage pool appears smaller than the advertised drive total.
UGOS Pro Reserves System Space
UGOS Pro requires approximately 16GB for system partitioning. File-system metadata also consumes some capacity, and the exact amount can vary by drive type and storage configuration.
The RAID Calculator includes an estimated system reservation, but the completed pool shown in Storage Manager remains the final reference.
How Much Capacity Do Common UGREEN NAS Configurations Provide?
The following examples use matching 8TB drives.
| Configuration | Capacity before system and file-system overhead | Drive-failure tolerance |
|---|---|---|
| 2 × 8TB in RAID 1 | 8TB decimal, approximately 7.3TiB | One drive |
| 4 × 8TB in RAID 5 | 24TB decimal, approximately 21.8TiB | One drive |
| 4 × 8TB in RAID 6 | 16TB decimal, approximately 14.6TiB | Any two drives |
| 4 × 8TB in RAID 10 | 16TB decimal, approximately 14.6TiB | One drive; a second failure is survivable only if it occurs in a different mirror pair. Losing both drives in the same pair causes the array to fail. |
The same rules apply to other matching drive sizes. Four 6TB drives provide 18TB of decimal data capacity in RAID 5, or approximately 16.4TiB before further overhead. RAID 6 provides 12TB decimal, or approximately 10.9TiB.
Capacity alone should not determine the RAID level. Use our guide to choosing the best RAID for a home NAS to compare failure tolerance, rebuild behavior, performance, and future expansion.
How Do Different Drive Sizes Affect the Calculation?
Standard RAID configurations normally use the smallest participating drive as the effective size of every member.
Consider a RAID 5 pool with one 8TB drive and three 16TB drives:
- Installed raw capacity: 56TB
- Capacity recognized for RAID calculation: 32TB
- Capacity allocated to parity: 8TB
- Decimal data capacity: 24TB
- Capacity left unused by the size mismatch: 24TB
Each 16TB drive contributes only 8TB because the smallest member is 8TB. The remaining 8TB on each larger drive cannot participate in that RAID 5 pool.
JBOD behaves differently because it combines participating drive capacities rather than limiting every member to the smallest drive. However, JBOD provides no drive-failure redundancy, and a failed member can make the combined storage pool and its data unavailable.
Matching drive capacities makes usable space, replacement planning, and future expansion easier to predict.
Which RAID Levels Fit Your UGREEN NAS?
Drive count determines which storage modes can be created:
- A two-bay UGREEN NAS can use Basic, JBOD, RAID 0, or RAID 1.
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- RAID 5 requires at least three participating drives.
- RAID 6 requires at least four participating drives.
- RAID 10 requires at least four drives and an even number of members.
Four-bay and larger UGREEN NAS models provide the drive count required for RAID 5, RAID 6, and RAID 10, subject to model support and the drives selected for the storage pool.
The calculator recommends compatible UGREEN NAS models based on the planned drive count. Confirm the model’s supported storage modes before purchasing the enclosure or drives.
What Does the RAID Calculator Not Calculate?
The UGREEN RAID Calculator is designed to estimate a new storage configuration. It does not predict:
- Read or write performance
- RAID rebuild duration
- Drive-failure probability
- Existing-pool RAID migration
- Whether a storage pool can be expanded without recreation
- Capacity consumed by future files, applications, snapshots, or file versions
The calculator also has no separate Hot Spare input. When planning three active 8TB drives in RAID 5 plus one 8TB Hot Spare, enter the three active RAID members in the calculator. The spare occupies a drive bay but contributes no usable or parity capacity until UGOS Pro assigns it to replace a failed member.
A UGOS Pro Hot Spare must be an HDD rather than an SSD. It must be unused, healthy, installed in an available internal HDD bay, and at least as large as the smallest active RAID member. Assigning an HDD as a Hot Spare erases the data already stored on it.
Plan the Storage Pool Before Buying Drives
Start with the amount of data you need to store, add room for expected growth, and then use the UGREEN NAS RAID Calculator to compare supported configurations.
Pay attention to all four results—not only available capacity. Protection shows the capacity committed to redundancy, unused space reveals inefficient drive combinations, and the system reservation explains part of the difference between theoretical RAID capacity and the final pool shown in UGOS Pro.
UGREEN RAID Calculator FAQs
Does the UGREEN RAID Calculator show exact final capacity?
No. It provides a planning estimate based on the selected drives and storage mode. UGOS Pro system partitioning, file-system metadata, and final disk formatting can change the result. Confirm the completed pool capacity in Storage Manager.
Can I use different-sized drives in the same RAID array?
Yes, but standard RAID configurations normally calculate capacity using the smallest participating drive. The additional capacity on larger drives becomes unused. Matching drive capacities provides more predictable space utilization.
Does the RAID Calculator include a Hot Spare?
No. Enter only the drives that will actively participate in the RAID. For three active RAID 5 members plus one Hot Spare, calculate the three active drives. A UGOS Pro Hot Spare must be an HDD; an SSD cannot be assigned as one. The spare must be unused and at least as large as the smallest active RAID member. Assigning the HDD as a Hot Spare erases all data stored on it.
Does RAID replace a backup?
No. RAID can keep a storage pool available after specified drive failures, but it cannot recover files deleted, overwritten, corrupted, or encrypted by ransomware. Important data should also exist in an independent backup.
