This estimator compares Unraid's two array write modes for your setup: Read/Modify/Write (the default, often called Normal Write) and Turbo Write (reconstruct write). It shows the array side speed range from Unraid's documentation, the network, source or small file limit of your transfer, the end to end speed, which drives work in each mode, and, with your drive watts and an Australian electricity rate, what Turbo Write adds in power. It also shows what changes when files land on a cache pool first and the Mover writes them to the array later.
Turbo Write raises what the array can take, but a copy is only as fast as its slowest stage. Over a 1 GbE network, from an internet download or with many small files, that stage is often not the array, and Turbo Write then gains little. Speeds are in decimal units (1 MB/s is 1,000,000 bytes a second; 1 GbE is 125 MB/s before overhead). Facts checked against Unraid 7.3.3.
1. Your array
2. What you are writing, and from where
3. Power (optional)
Drive watts come from your drives' datasheets; NTK does not assume them.
End to end:
Drives working:
Power:
End to end:
Drives working:
Power:
| Mode | What happens on a write | Drives working | Typical array speed | Power |
|---|---|---|---|---|
| Read/Modify/Write (the default) | Read/Modify/Write is the default; only the parity drive and the target data drive spin up. (Unraid documentation, checked 2026-10-07) | The target data drive and parity (2 drives with one parity disk, 3 with two) | Typically 20 to 40 MB/s | Fewer drives working |
| Turbo Write (reconstruct write) | Turbo Write reads all the other data drives and writes new data and parity together; every array drive must be working and spinning. (Unraid documentation, checked 2026-10-07) | Every array drive | Typically 40 to 120 MB/s | Every drive spinning and working |
| Pool first, Mover later | Primary storage is where a share's new files are first written: a cache pool, the array, or any named pool. The Mover later moves the files to the array. (Unraid documentation, checked 2026-10-07) | The pool device(s) now; the array drives during the Mover run | Pool speed now; the array mode's range during the Mover run | Array drives spin for the Mover run |
| Auto | Unraid's docs still describe the Auto write mode as a future feature that would use Turbo Write only when all drives are already spinning. (Unraid documentation, checked 2026-10-07) | Not available yet | Not available yet | Not available yet |
Unraid's documentation gives typical array write speeds of 20 to 40 MB/s for Read/Modify/Write (the default) and 40 to 120 MB/s for Turbo Write (reconstruct write), which needs every array drive spinning and healthy. (Unraid documentation)
Array side. Each write mode uses Unraid's documented typical range, the same for any number of drives: Unraid documents one range per mode, and the calculator adds no bonus for more drives and no penalty for dual parity. A speed you measured replaces the range. SMR drives and SSDs in the array lower the confidence, with Unraid's caveat, and no fixed penalty.
End to end. A write is as fast as its slowest stage: the array, the network (the link's line rate less protocol overhead, an NTK planning assumption), an internet plan, the pool being read during a Mover run, or a source you measured. For a job size, every file also costs a few milliseconds of handling, which dominates with many small files. The limit is reported for each end of the range, because the slow and fast ends can be limited by different stages.
Pool first. A file written to a cache pool is not an array write yet: it lands at the pool's speed (or the source's, if slower), and the Mover moves it to the array later, where the write mode applies. The calculator then compares the modes for that Mover run.
Drives and power. Read/Modify/Write keeps the target data drive and parity working; Turbo Write needs every array drive. Drives not working draw your idle watts if spinning, or your spun down watts. The cost uses the electricity rate for the state you pick, from NTK's Australian rate data, or your own rate.
| State | Rate (c/kWh) | Source | Date |
|---|---|---|---|
| NSW | 34.0 | AER DMO 8 Final Determination 26 May 2026, Section 9(1), avg of 3 NSW zones | September 2026 |
| VIC | 28.2 | ESC Victorian Default Offer 2026-27 domestic flat tariff, avg of 5 distribution zones | September 2026 |
| QLD | 28.0 | AER DMO 8 Final Determination 26 May 2026, Section 9(1), Energex flat rate (SE Queensland) | September 2026 |
| SA | 41.9 | AER DMO 8 Final Determination 26 May 2026, Section 9(1) SA Power Networks flat rate | September 2026 |
| WA | 33.3 | Synergy Home Plan (A1) from 1 Jul 2026 (WA Government-set tariff) | September 2026 |
| TAS | 24.8 | Aurora Energy Tariff 32 Residential Single Rate from 1 Jul 2026 (OTTER-approved standing offer) | September 2026 |
| ACT | 37.0 | ActewAGL ACT Standard plan from 1 Jul 2026 (ICRC standing offer), Home all usage | September 2026 |
| NT | 31.7 | Jacana Energy regulated residential tariff from 1 Jul 2026 | September 2026 |
Method last reviewed: 2026-10-07. Unraid facts last checked at source: 2026-10-07. Electricity rates dated from: 2026-09-25.
| Fact | Source | Checked |
|---|---|---|
| Array write modes (Unraid) | ||
| Unraid's documentation gives typical array write speeds of 20 to 40 MB/s for Read/Modify/Write (the default) and 40 to 120 MB/s for Turbo Write (reconstruct write), which needs every array drive spinning and healthy. | Unraid documentation | 2026-10-07 |
| Read/Modify/Write is the default; only the parity drive and the target data drive spin up. | Unraid documentation | 2026-10-07 |
| Turbo Write reads all the other data drives and writes new data and parity together; every array drive must be working and spinning. | Unraid documentation | 2026-10-07 |
| Unraid advises against Turbo Write for small or infrequent writes, because every write spins up all drives. | Unraid documentation | 2026-10-07 |
| Unraid says the default write mode offers the best balance for most users unless they need higher speeds. | Unraid documentation | 2026-10-07 |
| Unraid's docs still describe the Auto write mode as a future feature that would use Turbo Write only when all drives are already spinning. | Unraid documentation | 2026-10-07 |
| Unraid's docs mention community plugins (search Turbo Write in the Apps tab) that may automate or schedule the write mode. | Unraid documentation | 2026-10-07 |
| Unraid does not stripe across drives: each file is stored on a single disk. | Unraid documentation | 2026-10-06 |
| Drives in the array (Unraid) | ||
| For array devices with sustained writes, particularly parity, the docs prefer CMR over drive-managed SMR; SMR can have significantly lower sustained write performance during parity syncs and rebuilds. | Unraid documentation | 2026-10-06 |
| Unraid does not support TRIM/Discard for SSDs in the main array and says to keep SSDs for pools. | Unraid documentation | 2026-10-07 |
| Unraid's documentation gives typical sequential speeds of 70 to 250 MB/s for a single hard drive (depending on model, age and where the data sits) and 400 to 550 MB/s for a SATA SSD. | Unraid documentation | 2026-10-07 |
| Pool first, Mover later (Unraid) | ||
| Primary storage is where a share's new files are first written: a cache pool, the array, or any named pool. | Unraid documentation | 2026-10-07 |
| Unraid's docs say the Mover typically moves cached data to the array at 3:40 AM. | Unraid documentation | 2026-10-07 |
| Data on a cache pool has no parity protection until it is moved to the array. | Unraid documentation | 2026-10-07 |
| Small files (Microsoft) | ||
| Copying large numbers of small files (under 1 MB each) is slow by design with single-threaded copy tools: every file has a fixed creation cost, so more time goes on creating files than on moving their data. | Microsoft Learn | 2026-10-07 |
| Unraid version | ||
| Latest stable Unraid OS release is 7.3.3 (docs release notes: 7.3.3 dated 2026-10-08). | Unraid documentation | 2026-10-12 |
| Unraid 7.4.0 is still a release candidate (7.4.0-rc.1, 2026-10-08), so 7.3.3 remains the current stable release (unraid_evidence current_version). | Unraid documentation | 2026-10-12 |
The calculator models Unraid's own write modes. Community plugins can switch the mode for you; they are not part of Unraid, and NTK does not model them.
CA Auto Turbo Write Mode is a third party plugin by Squid (shown as Administrators on the forum), first posted 12 March 2017, that switches Turbo Write on or off by how many drives are spinning, installed from the Apps tab.
The newest post in the CA Auto Turbo Write Mode thread (page 7 of 7) is by its author Squid on 6 November 2025.
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