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For most homes and small offices, start with six matched 4TB NAS hard drives. That gives 24TB of raw capacity and approximately 20TB usable in RAID 5 before filesystem formatting and reserved space. Choose six 8TB drives for about 40TB usable, or six 12TB drives for about 60TB usable, if your files, backups, media library or business data are growing quickly.
The right purchase depends on usable capacity after RAID, how many drive failures you want to survive, future expansion, and whether you need SSD performance. The six-bay enclosure is diskless, so the drives you install determine nearly all of its storage capacity.
What the Ugreen NASync IDX6011 Pro can hold
UGREEN’s official specification lists six SATA drive bays, two M.2 NVMe slots and support for JBOD, Basic, RAID 0, RAID 1, RAID 5, RAID 6 and RAID 10. Its stated maximum configuration is 208TB: six 32TB SATA drives plus two 8TB NVMe drives. That figure is a configured raw ceiling, not the amount of space you will see in a redundant array.
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The enclosure includes a 128GB system SSD. The operating system therefore does not consume one of the six front SATA bays, leaving all six bays available for your data drives. The two M.2 slots are separate from the HDD capacity and can be used for cache or an SSD storage pool.
#1 Best Overall
- IronWolf internal hard drives are the ideal solution for up to 8-bay, multi-user NAS environments craving powerhouse performance
- Store more and work faster with a NAS-optimized hard drive providing ultra-high capacity up to 16TB and cache of up to 256MB
- Purpose built for NAS enclosures, IronWolf delivers less wear and tear, little to no noise/vibration, no lags or down time, increased file-sharing performance, and much more
- Easily monitor the health of drives using the integrated IronWolf Health Management system and enjoy long-term reliability with 1M hours MTBF
- Three-year limited warranty protection plan included and three year Rescue Data Recovery Services included
How much usable space will you get?
Usable capacity depends on the number of drives, each drive’s size and the RAID level. In RAID 5, one drive’s worth of capacity is reserved for distributed parity. A simple planning formula is:
RAID 5 usable capacity ≈ (number of drives − 1) × capacity of the smallest drive
Actual reported capacity is lower after filesystem formatting, system reservations and the difference between decimal terabytes sold by drive manufacturers and the units displayed by operating systems.
| Drive layout | Raw capacity | Approximate RAID 5 capacity before filesystem overhead | Evidence or qualification |
|---|---|---|---|
| Four 4TB SATA drives | 16TB | 12TB | TechRadar reported 12TB usable with four 4TB Western Digital drives in RAID 5. |
| Six 4TB SATA drives | 24TB | 20TB | Tom’s Guide measured this result with six 4TB Seagate IronWolf drives. |
| Six 8TB SATA drives | 48TB | Approximately 40TB | Planning arithmetic based on one drive of parity; not a cited benchmark. |
| Six 12TB SATA drives | 72TB | Approximately 60TB | Planning arithmetic based on one drive of parity; not a cited benchmark. |
| Six 16TB SATA drives | 96TB | Approximately 80TB | Planning arithmetic based on one drive of parity; not a cited benchmark. |
For example, Tom’s Guide’s six-drive setup used 4TB of the 24TB raw total for parity and reported 20TB usable. The same one-drive-parity calculation scales to larger, equal-sized drives, but your NAS will report somewhat less after formatting.
Choosing a drive size
Six 4TB drives: the sensible baseline
Six 4TB NAS-rated SATA drives are a practical starting point for photo libraries, documents, home video, PC backups and a moderate media collection. Approximately 20TB in RAID 5 leaves room for growth while using every bay. It also gives RAID 5 one-drive fault tolerance, so the array can remain available while a failed drive is replaced and rebuilt.
Rank #2
- Available in capacities ranging from 2TB to 12TB
- For RAID-optimized NAS systems with up to 8 bays
- Designed for Continuous Operation
- Backed by World-Class Support and Warranty
- Tuned for NAS with NASware
Do not treat 20TB as 20TB of disposable working room. Keep free space for snapshots, temporary files, application data and rebuild operations. If your current data already approaches 12–15TB, six 4TB drives may leave too little headroom after backups and future growth.
Six 8TB drives: a better growth buffer
Six 8TB drives provide 48TB raw and roughly 40TB in RAID 5. This option suits households with large 4K video collections, several computers making image backups, or small offices storing shared project files. Larger drives usually cost more per unit, and a failed drive can take longer to rebuild, but the array offers twice the approximate RAID 5 capacity of the six-drive 4TB layout.
Six 12TB drives: for sustained expansion
Six 12TB drives provide 72TB raw and approximately 60TB in RAID 5. Consider this tier when your data is growing by several terabytes each year, when you retain multiple backup versions, or when replacing the enclosure later would be difficult. The purchase cost, power draw and acoustic output can be higher than with smaller disks, so check the room in which the NAS will operate.
Six 16TB drives and larger
Six 16TB drives produce 96TB raw and roughly 80TB in RAID 5. This is appropriate only when your data plan justifies the capital cost and you have a separate backup target capable of holding the important data. The enclosure’s 208TB stated maximum uses six 32TB SATA drives and two 8TB NVMe drives, but that maximum does not mean a redundant RAID 5 volume will expose 208TB to applications.
RAID level changes the answer
| RAID mode | Usable-capacity pattern | Drive-failure tolerance | When it makes sense |
|---|---|---|---|
| Basic or JBOD | Close to the sum of installed drives, subject to formatting | No array-level redundancy | Separate volumes, scratch data or data already protected elsewhere. |
| RAID 0 | Close to the sum of all drives | None; one failed drive can destroy the array | Speed for replaceable data, never the only copy of important files. |
| RAID 1 | Approximately the capacity of one drive in a mirror | Typically one drive, depending on the mirror layout | Small arrays where redundancy matters more than capacity. |
| RAID 5 | Approximately total capacity minus one drive | One drive | Balanced capacity and availability for many six-bay deployments. |
| RAID 6 | Approximately total capacity minus two drives | Two drives | Large arrays, long rebuild windows or data that must remain online through a second failure. |
| RAID 10 | Approximately half of total capacity | At least one drive, with the exact outcome depending on which mirror fails | High I/O workloads such as virtual machines and databases. |
RAID 5 is why six 4TB drives yield about 20TB rather than 24TB. RAID 6 would reserve about two drive capacities, leaving roughly 16TB with six 4TB drives, 32TB with six 8TB drives, 48TB with six 12TB drives and 64TB with six 16TB drives. Those are planning estimates; formatting and system overhead reduce the displayed figure.
Rank #3
- Enterprise-Class Performance – 7200 RPM speed with SATA 6Gb/s interface ensures fast data transfer and reliable throughput for servers and storage arrays
- Built for 24/7 Operation – Designed for continuous use in demanding environments such as data centers, NAS, and RAID systems
- High Workload Capacity – Supports heavy read/write workloads, making it ideal for business-critical applications
- Enhanced Reliability – Advanced vibration protection and error recovery technology help maintain data integrity and system stability
- Versatile Compatibility – 3.5-inch form factor compatible with desktops, servers, NAS, and surveillance storage systems
RAID is not a backup
RAID protects availability when a drive fails; it does not create an independent copy. A controller or filesystem error, accidental deletion, malware, theft, fire or power event can affect every disk in the array. Keep a separate backup of irreplaceable photos, documents, recordings and project files. Test that backup by restoring representative files, not merely by checking that a backup job says “complete.”
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Use equal-capacity, compatible SATA drives whenever possible. Dong Knows Tech reports that when capacities are mixed in a RAID array, the smallest drive’s capacity is applied to all drives. Mixing an 8TB disk with 12TB disks can therefore leave part of the larger disks unused.
Plan the array around the next few years rather than assuming you can expand cheaply later. The same review reports that UGOS Pro does not provide a safe in-place expansion path by replacing existing disks with larger ones. A future capacity increase may require a new array and a complete backup-and-restore migration, so buying larger matched drives now can be less disruptive than replacing them one at a time.
When NVMe SSDs are worth adding
The two M.2 slots accept NVMe SSDs for cache or an SSD storage pool. TechRadar used two 1TB NVMe drives as cache while four HDDs supplied bulk storage. Budget this separately from the six-bay capacity: a 1TB or 2TB cache does not add an equivalent amount of space to an HDD RAID volume.
Use NVMe cache for active, latency-sensitive work
- Metadata-heavy file shares with many small files.
- Virtual machines and containers.
- Databases or application data with frequent random reads and writes.
- Active photo, video or software projects where many users access the same working set.
Cache cannot replace a backup, and it does not turn a hard-drive array into an all-SSD system. If your workload is mostly sequential media playback or occasional workstation backups, spending the budget on larger HDDs and a robust backup target usually provides more useful capacity.
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- Massive 4TB Capacity — Ideal for enterprise storage, data centers, NAS/SAN arrays, and backup solutions requiring reliable high-density storage per drive bay.
- SATA 6Gb/s Interface — Delivers fast, reliable data transfer with broad compatibility across enterprise servers, storage arrays, and RAID controllers.
- CMR Recording Technology — Utilizes Conventional Magnetic Recording for consistent write performance, well-suited for demanding, write-intensive workloads.
- 7200 RPM Performance with 256MB Cache — Delivers strong sustained transfer rates and low latency for high-throughput applications, backed by Non-Volatile Cache (NVC) for improved write performance and data protection.
- Enterprise-Grade Reliability — Rated for 24/7 operation with a 2 million hour MTBF and 550TB/year workload rating, backed by a dual-stage micro actuator for enhanced positioning accuracy.
Use an SSD pool when applications need predictable latency
An SSD storage pool places selected workloads on the NVMe drives rather than merely accelerating an HDD volume. This can be useful for virtual machines, containers or databases that do not need tens of terabytes. Keep bulk media and archival files on the HDD array, and verify the redundancy and backup behavior of the SSD pool before storing unique data there.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.A practical sizing method
- Measure current data. Add the occupied space on computers, phones, external disks and existing servers. Separate replaceable downloads from irreplaceable files.
- Project growth. Estimate annual additions from camera footage, business projects, surveillance recordings and backup versions. Multiply by the number of years before you expect to replace or migrate the NAS.
- Add working headroom. Leave room for snapshots, temporary exports, package updates and rebuild activity instead of planning to fill the volume completely.
- Select fault tolerance. Choose RAID 5 when one-drive protection and capacity balance are acceptable; choose RAID 6 when a second drive failure during a long rebuild is a serious concern; choose RAID 10 for performance-sensitive workloads.
- Buy matched drives. Keep capacity and model families consistent, check SATA compatibility and install enough drives to avoid an early migration.
- Decide on NVMe. Add M.2 SSDs only when your workload benefits from cache or an SSD pool. They are optional for ordinary file storage.
- Prepare backup capacity. Ensure the independent backup destination can hold the data that would be costly or impossible to recreate.
Which configuration fits common users?
| User profile | Reasonable starting point | Why |
|---|---|---|
| Home documents, photos and computer backups | Six 4TB drives in RAID 5 | Approximately 20TB before overhead, with one-drive fault tolerance. |
| Large media library or several years of backups | Six 8TB drives in RAID 5 | Approximately 40TB and more room for growth without changing the bay count. |
| Small office with rapid file growth | Six 12TB drives in RAID 6 | Approximately 48TB before overhead while tolerating two drive failures. |
| Virtual machines or databases | HDD RAID for bulk data plus a redundant NVMe pool or cache | Separates high-capacity storage from latency-sensitive workloads. |
These are starting points, not guarantees of performance or future cost. Compare current drive prices per usable terabyte, expected noise and power consumption, warranty terms and the cost of maintaining a second backup copy before ordering.
Installation and capacity checks
- Install the matched SATA drives in the six bays and connect the NAS to reliable power, ideally through a UPS.
- Open the UGOS Pro setup wizard, confirm that every drive is detected at its expected capacity and create the selected RAID level.
- Wait for initialization and parity synchronization to complete before treating the volume as ready for production data.
- Record the capacity shown by UGOS Pro after formatting; it will be lower than the decimal raw total printed on the drive boxes.
- Configure alerts for drive health, temperature, degraded arrays and failed backups.
- Copy a small test set, verify permissions and restore a file from the independent backup before moving all data.
If a drive is reported with a smaller capacity than expected, stop before creating the array and check cabling, drive health and compatibility. Replacing a disk in a degraded RAID array can take many hours; avoid heavy workloads during a rebuild and keep the separate backup current.
Bottom line for the IDX6011 Pro
Six matched 4TB drives in RAID 5 are the sensible baseline for most home and small-office users: approximately 20TB usable before filesystem overhead. Choose six 8TB drives for roughly 40TB, or six 12TB drives for roughly 60TB, when growth justifies the higher purchase cost. Select RAID 6 instead of RAID 5 when two-drive fault tolerance matters more than capacity, and add NVMe only for workloads that benefit from cache or an SSD pool. Whatever configuration you choose, keep an independent backup because no RAID mode is a backup.
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