Interactive capacity planning
Synology RAID / SHR Calculator: Usable Capacity Planner
The useful question is not raw drive total; it is how much capacity remains after the chosen redundancy scheme can protect each drive region. This calculator estimates SHR-1 and SHR-2 by grouping matching capacity regions, while classic RAID 1/5/6 estimates are constrained by the smallest member drive. Filesystem formatting, DSM reservations and vendor decimal-versus-binary reporting will make the displayed NAS number smaller.
Quick answer
Use the calculator before buying a mismatched set
Enter the actual capacities you plan to install. A mixed-drive SHR set can sometimes use capacity that RAID 5 or RAID 6 leaves idle, but unmatched top portions still remain unavailable until enough larger drives exist to form a protected region.
Live Amazon products
Hardware relevant to this technical workflow
This Sprint 9F catalogue is intentionally focused on current and previous Synology Plus systems. Storage-repair pages can also read compatible third-party NAS hard-drive data from Cloudzat Storage Price Intelligence in read-only mode. Product cards support the decision; they never override current Synology compatibility or model-specific repair rules.
Technical decision
Capacity estimates are planning numbers
The tool does not create a storage pool and cannot see model-specific RAID restrictions. Use it to compare configurations, then verify the exact supported RAID types in the product specification and DSM.
Interactive technical tool
Synology RAID / SHR Capacity Calculator
Use this as a planning aid. It identifies capacity, redundancy, deployment or repair constraints, but it does not replace the current Synology model manual, DSM documentation or upstream application release notes.
Technical safety checklist
Four checks before changing a production NAS
Protect data before maintenance
A healthy RAID state is not a backup. Confirm an independent restorable copy before repairs, DSM upgrades, RAID migration or major container changes.
Change one layer at a time
Storage, DSM, networking and application changes should be separated so an unexpected result can be traced to one action rather than several.
Record the exact state
Write down model, DSM build, pool type, drive serials, ports, mapped folders and current application versions before modifying a production NAS.
Verify the result
A repair or upgrade is complete only after storage health, services, backups and representative restores behave as expected.
Raw capacity is only the starting number
Raw capacity is only the starting number is central to Synology RAID / SHR Calculator: adding the drive labels together ignores redundancy, mismatched-capacity waste and filesystem overhead. For Synology RAID / SHR Calculator, record the capacity-estimator path baseline before action. When checking raw capacity is only the starting number, compare the capacity-estimator path result with that earlier capacity-estimator path baseline.
A tested backup protects the capacity-estimator path workflow during raw capacity is only the starting number. For Synology RAID / SHR Calculator, recovery of the capacity-estimator path state matters more than speed.
Classic RAID uses the smallest member
For Synology RAID / SHR Calculator, classic raid uses the smallest member matters because RAID 5 and RAID 6 capacity planning is anchored to the smallest drive because every stripe must fit across all participating members. For Synology RAID / SHR Calculator, record the capacity-estimator path baseline before action. When checking classic raid uses the smallest member, compare the capacity-estimator path result with that earlier capacity-estimator path baseline.
Document the capacity-estimator path decision around classic raid uses the smallest member. In Synology RAID / SHR Calculator, record why the capacity-estimator path state changed and what outcome the capacity-estimator path procedure expects.
SHR works in protected capacity regions
Inside Synology RAID / SHR Calculator, the practical constraint is this: Synology can partition larger disks into regions and combine matching regions into additional redundant arrays, which is why mixed sizes can be more efficient. For Synology RAID / SHR Calculator, record the capacity-estimator path baseline before action. When checking shr works in protected capacity regions, compare the capacity-estimator path result with that earlier capacity-estimator path baseline.
Keep shr works in protected capacity regions separate from other capacity-estimator path changes. On Synology RAID / SHR Calculator, isolating the capacity-estimator path work makes a failure in the capacity-estimator path path easier to identify.
SHR-1 needs redundant pairs or larger groups
The Synology RAID / SHR Calculator reason to study shr-1 needs redundant pairs or larger groups is straightforward: a top capacity region that exists on only one drive cannot become protected usable space. For Synology RAID / SHR Calculator, record the capacity-estimator path baseline before action. When checking shr-1 needs redundant pairs or larger groups, compare the capacity-estimator path result with that earlier capacity-estimator path baseline.
Before buying hardware for shr-1 needs redundant pairs or larger groups, decide whether the capacity-estimator path target is capacity, redundancy or availability; verify the resulting capacity-estimator path outcome directly.
SHR-2 needs more matching members
Synology RAID / SHR Calculator planning can fail here because two-drive tolerance means a capacity region needs enough participating drives to survive two failures, so unmatched upper regions are more likely to remain idle. For Synology RAID / SHR Calculator, record the capacity-estimator path baseline before action. When checking shr-2 needs more matching members, compare the capacity-estimator path result with that earlier capacity-estimator path baseline.
In Synology RAID / SHR Calculator, make the capacity-estimator path step reversible. Back up the capacity-estimator path state; change one variable for shr-2 needs more matching members; verify the capacity-estimator path result before continuing.
Decimal terabytes differ from DSM display
A safer Synology RAID / SHR Calculator interpretation starts with one fact: drive vendors advertise decimal TB while operating systems often display binary-derived values, so do not treat a label-size estimate as exact formatted capacity. For Synology RAID / SHR Calculator, record the capacity-estimator path baseline before action. When checking decimal terabytes differ from dsm display, compare the capacity-estimator path result with that earlier capacity-estimator path baseline.
If a tutorial conflicts with the capacity-estimator path behavior on Synology RAID / SHR Calculator, stop at decimal terabytes differ from dsm display; follow the model-specific Synology instructions for the capacity-estimator path condition.
Snapshots and application data consume the result
Snapshots and application data consume the result is central to Synology RAID / SHR Calculator: usable storage is not the same as free storage after Btrfs metadata, snapshots, package databases, thumbnails and container volumes are added. For Synology RAID / SHR Calculator, record the capacity-estimator path baseline before action. When checking snapshots and application data consume the result, compare the capacity-estimator path result with that earlier capacity-estimator path baseline.
A tested backup protects the capacity-estimator path workflow during snapshots and application data consume the result. For Synology RAID / SHR Calculator, recovery of the capacity-estimator path state matters more than speed.
Expansion can change the efficiency later
For Synology RAID / SHR Calculator, expansion can change the efficiency later matters because replacing another member with a larger disk can unlock capacity that was previously stranded in an unmatched region. For Synology RAID / SHR Calculator, record the capacity-estimator path baseline before action. When checking expansion can change the efficiency later, compare the capacity-estimator path result with that earlier capacity-estimator path baseline.
Document the capacity-estimator path decision around expansion can change the efficiency later. In Synology RAID / SHR Calculator, record why the capacity-estimator path state changed and what outcome the capacity-estimator path procedure expects.
RAID migration rules remain separate
Inside Synology RAID / SHR Calculator, the practical constraint is this: a configuration that calculates well may not be reachable from the current pool through an in-place RAID type change. For Synology RAID / SHR Calculator, record the capacity-estimator path baseline before action. When checking raid migration rules remain separate, compare the capacity-estimator path result with that earlier capacity-estimator path baseline.
Keep raid migration rules remain separate separate from other capacity-estimator path changes. On Synology RAID / SHR Calculator, isolating the capacity-estimator path work makes a failure in the capacity-estimator path path easier to identify.
Performance is not calculated here
The Synology RAID / SHR Calculator reason to study performance is not calculated here is straightforward: usable capacity says nothing reliable about IOPS, sequential throughput, rebuild duration or application responsiveness. For Synology RAID / SHR Calculator, record the capacity-estimator path baseline before action. When checking performance is not calculated here, compare the capacity-estimator path result with that earlier capacity-estimator path baseline.
Before buying hardware for performance is not calculated here, decide whether the capacity-estimator path target is capacity, redundancy or availability; verify the resulting capacity-estimator path outcome directly.
Backups need their own capacity budget
Synology RAID / SHR Calculator planning can fail here because a larger usable pool often means a larger backup target, longer cloud seed time and more expensive restore path. For Synology RAID / SHR Calculator, record the capacity-estimator path baseline before action. When checking backups need their own capacity budget, compare the capacity-estimator path result with that earlier capacity-estimator path baseline.
In Synology RAID / SHR Calculator, make the capacity-estimator path step reversible. Back up the capacity-estimator path state; change one variable for backups need their own capacity budget; verify the capacity-estimator path result before continuing.
Treat the output as a purchase comparison
A safer Synology RAID / SHR Calculator interpretation starts with one fact: the best use of the calculator is deciding whether the cost of larger disks, deeper redundancy or more bays produces enough protected capacity for the workload. For Synology RAID / SHR Calculator, record the capacity-estimator path baseline before action. When checking treat the output as a purchase comparison, compare the capacity-estimator path result with that earlier capacity-estimator path baseline.
If a tutorial conflicts with the capacity-estimator path behavior on Synology RAID / SHR Calculator, stop at treat the output as a purchase comparison; follow the model-specific Synology instructions for the capacity-estimator path condition.
Questions people ask
Synology RAID / SHR Calculator: common questions
Is this the same as Synology’s official RAID Calculator?
No. It is a Cloudzat planning tool based on documented RAID and SHR capacity behavior; verify final configurations with Synology.
For Synology RAID / SHR Calculator, "Is this the same as Synology’s official RAID Calculator?" depends on the capacity-estimator path: check the exact DSM build for the capacity-estimator path, the NAS model, and the current capacity-estimator path state.
Does the calculator include filesystem overhead?
No. It estimates protected usable capacity before filesystem and DSM overhead.
For Synology RAID / SHR Calculator, "Does the calculator include filesystem overhead?" depends on the capacity-estimator path: check the exact DSM build for the capacity-estimator path, the NAS model, and the current capacity-estimator path state.
Why does SHR show more space than RAID 5 with mixed drives?
SHR can form additional protected regions from the larger portions of multiple disks, while classic RAID 5 is limited by the smallest drive.
For Synology RAID / SHR Calculator, "Why does SHR show more space than RAID 5 with mixed drives?" depends on the capacity-estimator path: check the exact DSM build for the capacity-estimator path, the NAS model, and the current capacity-estimator path state.
Why is some SHR capacity still unused?
An unmatched capacity region cannot be exposed without enough other drives to protect it at the selected redundancy level.
For Synology RAID / SHR Calculator, "Why is some SHR capacity still unused?" depends on the capacity-estimator path: check the exact DSM build for the capacity-estimator path, the NAS model, and the current capacity-estimator path state.
Can I use different brands in the same pool?
Brand mixing and RAID capacity are separate questions. Verify model compatibility, sector format and current Synology guidance.
For Synology RAID / SHR Calculator, "Can I use different brands in the same pool?" depends on the capacity-estimator path: check the exact DSM build for the capacity-estimator path, the NAS model, and the current capacity-estimator path state.
Does the result include hot spare capacity?
No. A hot spare is not part of the active protected usable capacity until it replaces a failed member.
For Synology RAID / SHR Calculator, "Does the result include hot spare capacity?" depends on the capacity-estimator path: check the exact DSM build for the capacity-estimator path, the NAS model, and the current capacity-estimator path state.
Can the tool calculate RAID 10?
This Sprint focuses on SHR-1, SHR-2, RAID 1, RAID 5 and RAID 6, which cover the main Synology comparison intents targeted here.
For Synology RAID / SHR Calculator, "Can the tool calculate RAID 10?" depends on the capacity-estimator path: check the exact DSM build for the capacity-estimator path, the NAS model, and the current capacity-estimator path state.
Does larger capacity mean faster rebuilds?
No. Larger drives often increase the amount of data that must be processed during repair.
For Synology RAID / SHR Calculator, "Does larger capacity mean faster rebuilds?" depends on the capacity-estimator path: check the exact DSM build for the capacity-estimator path, the NAS model, and the current capacity-estimator path state.
Can I enter zero for empty bays?
Yes. Empty entries should be treated as unused bays rather than zero-size members.
For Synology RAID / SHR Calculator, "Can I enter zero for empty bays?" depends on the capacity-estimator path: check the exact DSM build for the capacity-estimator path, the NAS model, and the current capacity-estimator path state.
Should I buy exactly the calculated capacity?
No. Add growth, snapshots, application overhead and backup headroom rather than designing a production NAS to run nearly full.
For Synology RAID / SHR Calculator, "Should I buy exactly the calculated capacity?" depends on the capacity-estimator path: check the exact DSM build for the capacity-estimator path, the NAS model, and the current capacity-estimator path state.
Official references and methodology
Verify the exact model, DSM build and application state
This Synology RAID / SHR Calculator guide uses primary documentation for the capacity-estimator path. Cloudzat evaluates the capacity-estimator path capacity, redundancy, deployment and recovery layers separately. Interactive capacity-estimator path results support planning; final capacity-estimator path changes need exact model guidance and current upstream documentation.
- Synology: What is Synology Hybrid RAID (SHR)?
- Synology: What RAID type is best for my storage?
- Synology: Replace a drive / expand storage capacity
- Synology: Repair a storage pool
As an Amazon Associate, Cloudzat may earn from qualifying purchases. Prices, NAS models, drive compatibility, DSM behavior and upstream application requirements can change. Verify the exact DiskStation model, current DSM documentation and application release notes before changing storage pools, replacing drives, exposing network services or upgrading production containers.