A 4 TB NAS backup takes roughly 10 hours over a 1GbE home network. And over 10 days if you're uploading to the cloud over an NBN 50 connection. Most people are shocked by this gap. The hardware benchmarks are fine, the backup software is set up correctly, and yet the first backup takes forever. The limiting factor may be the connection, but storage performance, file count, CPU-intensive processing and backup-software overhead can also determine backup speed. This guide breaks down realistic backup times for the setups most Australian NAS owners actually have, and explains what you can do when the numbers don't fit your maintenance window.
In short: Over a 1GbE home network, expect roughly 2.5 hours per TB for a full backup at real-world speeds (~110 MB/s). On a 50/20 NBN service, the theoretical minimum is about 111 hours per decimal TB at the full 20 Mbps upload cap; actual backups will take longer and vary by service. The initial full backup is always the slow part. Incremental backups are usually smaller than the initial backup, but they may take minutes or many hours depending on how much data changed and the available throughput. Use the Backup Time & Window Calculator to model your specific setup.
Why Backup Time Surprises People
Backup software benchmarks and vendor marketing typically quote the NAS's disk read speed or network interface throughput. Numbers like "1 Gbps" or "200 MB/s read." What they don't tell you is that these are theoretical maximums under ideal conditions, and that your backup job will almost certainly be bottlenecked by something slower: the destination write speed, the network link, or (for cloud and offsite backups) your internet upload connection.
There are three links in the backup chain: the source that reads data, the network that moves it, and the destination that writes it. The slowest of the three determines your actual backup speed. On a home LAN where both source and destination are connected over 1GbE, the practical ceiling is around 100-115 MB/s sustained. This can be slower than the sequential transfer rate of many current NAS HDDs, although real HDD performance varies with capacity, workload and disk location. Over NBN, the ceiling drops dramatically: a fixed-line 50/20 NBN service has a wholesale upload cap of 20 Mbps, or 2.5 MB/s before protocol and service overhead; measured upload throughput may be lower.
Full Backup Times: What to Expect on Australian Connections
The table below shows estimated full backup times for common dataset sizes across the connection types most Australian NAS owners have. These use real-world sustained throughput, not burst or theoretical maximums. NBN calculations must use the plan's upload cap, not a percentage of its download-tier name, and should be adjusted using the user's measured upload throughput.
Full Backup Time by Dataset Size and Connection Type
| 1GbE LAN (~110 MB/s) | NBN 50 Upload (up to 20 Mbps; use measured throughput) | NBN 100-class Upload (use the plan's stated upload cap and measured throughput) | 10GbE LAN (~500 MB/s) | |
|---|---|---|---|---|
| 500 GB | ~1h 16m | ~30h (1.3 days) | ~15h | ~17m |
| 1 TB | ~2h 35m | ~62h (2.6 days) | ~30h (1.3 days) | ~34m |
| 2 TB | ~5h 10m | ~124h (5.2 days) | ~60h (2.5 days) | ~1h 8m |
| 4 TB | ~10h 20m | ~248h (10.3 days) | ~121h (5 days) | ~2h 17m |
| 8 TB | ~20h 40m | ~496h (20.7 days) | ~242h (10 days) | ~4h 34m |
| 16 TB | ~41h 20m | ~993h (41 days) | ~484h (20 days) | ~9h 8m |
A few things stand out from this table. First, a 1GbE LAN backup of 4 TB takes just over 10 hours. At roughly 10 hours 20 minutes, it does not fit the article's nine-hour home window and leaves little margin in an 11-hour window. Second, that same backup over NBN 50 upload takes over 10 days. Completely incompatible with any reasonable maintenance window. Third, 10GbE makes a significant difference for large datasets: 4 TB in just over 2 hours versus all night on 1GbE. If you're backing up 8 TB or more to a local destination and time matters, 10GbE is worth considering.
The Initial Seed Problem. Why Your First Backup Is Always Slow
The initial full backup is the hardest part of any NAS backup strategy. There's no shortcut: you have to move all the data at least once. This is true whether you're backing up to another NAS on your LAN, to an external USB drive, or to the cloud. After the initial seed, everything changes. Incremental backups only move changed data, which is typically a small fraction of the total.
The mistake most NAS owners make is starting the initial backup at an arbitrary time, then discovering mid-week that it's still running and impacting network performance. The right approach is to treat the initial seed as a one-time project: schedule it for a Friday evening, accept that it will run over the weekend, and don't expect anything from your network while it's happening.
For cloud backups, the situation is more extreme. If you have a 4 TB dataset and an NBN 50 connection, the initial seed will take over 10 days at real-world upload speeds. During this time, your upload bandwidth will be saturated unless you configure bandwidth throttling in your backup software. Most NAS backup tools. Including Synology Hyper Backup and QNAP Hybrid Backup Sync. Support upload speed limits that let you cap the backup to, say, 50% of available upload bandwidth during business hours.
Local seed strategy for cloud backups: Some providers offer a provider-supplied transfer appliance or a specific offline-ingest workflow. Verify regional availability, minimum dataset, fees and the supported relinking procedure; do not assume the provider accepts a user-supplied USB drive. This can avoid weeks of online uploading, but end-to-end completion time also includes appliance delivery, return shipping and provider ingestion. Offline-ingest availability varies by provider, region, account type and dataset size, so confirm current eligibility before planning around it. Ask about "offline data transfer" or "seed import" options.
Full vs Incremental vs Differential: How Much Data Actually Moves Each Night
Once the initial seed is done, the ongoing backup strategy determines how long each nightly job takes. Understanding the three backup types is essential for fitting backups into a real maintenance window.
Full backups copy everything every time. A weekly full backup of 4 TB over 1GbE takes over 10 hours. Fine for a weekend, but it chews up your entire overnight window. Running full backups nightly on large datasets is almost never practical.
Incremental backups only copy data that has changed since the last backup (whether that was a full or another incremental). As an illustration, if 5% of a 4 TB dataset changes each day, roughly 200 GB changes per day. Over 1GbE, that incremental takes about 31 minutes. Over NBN 50, about 12 hours. Which is still a stretch for a standard overnight window, but far more manageable than a full backup.
Differential backups copy everything that has changed since the last full backup. They start small (Day 1 is similar to an incremental) and grow each day until the next full run. Differential backups generally grow between full backups, but their size depends on which data changes; in this illustration, Day 7 is about 1.4 TB, or 35% of the full dataset. Differential backups are faster to restore (you only need the last full plus one differential file), but they create more transfer volume than incrementals on a day-to-day basis.
Nightly Backup Time: 4 TB Dataset, 5% Daily Change Rate (~200 GB changed/day)
| 1GbE LAN (~110 MB/s) | NBN 50 Upload (~37 Mbps) | NBN 100 Upload (~75 Mbps) | |
|---|---|---|---|
| Full (4 TB) | ~10h 20m | ~248h (10+ days) | ~121h (5 days) |
| Incremental (~200 GB) | ~31m | ~12h 24m | ~6h 6m |
| Differential Day 3 (~600 GB) | ~1h 32m | ~37h | ~18h 12m |
| Differential Day 7 (~1.4 TB) | ~3h 35m | ~86h (3.6 days) | ~42h (1.75 days) |
The practical conclusion: for most home NAS owners, a weekly full backup (over the weekend) combined with nightly incrementals is the right strategy. The weekend full backup fits comfortably on 1GbE, and nightly incrementals typically complete in 30-60 minutes for datasets up to 4 TB with a normal change rate. This is exactly the strategy that Synology Hyper Backup and QNAP Hybrid Backup Sync are designed for. Both perform an initial full backup followed by incremental runs and support scheduled version retention; that is not the same as transmitting a new full backup every week.
NBN Upload Reality: Why Cloud Backup Is Hard in Australia
Australia's NBN upload speeds are one of the most under-discussed constraints in the NAS space. The upload tiers look reasonable on paper, but the real-world experience is consistently lower than advertised, and even the top residential tiers leave a lot to be desired for large backup workloads.
Typical real-world upload throughput for common NBN plans:
- NBN 25: upload is capped at 5 or 10 Mbps depending on the plan and access technology; use measured throughput for timing. Barely usable for anything beyond small incremental backups
- NBN 50: upload is capped at 20 Mbps on a 50/20 service, with actual throughput dependent on the service and access technology. The most common plan; practical for incrementals under ~200 GB, painful for anything larger
- For a 100 Mbps-class service, use the plan's stated upload cap and a measured upload speed; 75 Mbps should not be assumed. Workable for 500 GB incrementals, still slow for initial full backup of large datasets
- The former 250/25 FTTP/HFC tier was uplifted to 750/50 in September 2025. Backup timing must use the applicable upload cap and measured throughput, not the download-tier number.
NBN upload speeds are also asymmetric by design. You get more download than upload. For backup purposes, only upload speed matters, which is why NBN plans that look fast for streaming video can feel slow when you're trying to push data offsite.
There's also the CGNAT complication: CGNAT is generally an ISP policy rather than a feature of a particular NBN access technology. It prevents ordinary IPv4 port forwarding, but some providers offer an opt-out or static-IP option. Most self-hosted offsite backup setups rely on the backup software connecting out to the destination, which still works under CGNAT. But peer-to-peer setups or remote access via port forwarding will fail. Synology QuickConnect can fall back to a relay when direct access fails, while QNAP's CloudLink provides router-configuration-free access for supported services; these services do not necessarily relay every connection. Tailscale is one general-purpose option for establishing remote connectivity through CGNAT.
How to Estimate Your Backup Window
A backup window is the time available between when the last user finishes working and when the first user starts again. Typically overnight. For home users, this is roughly 10 PM to 7 AM (9 hours). For small businesses, it might be 8 PM to 7 AM (11 hours). The backup must complete before the window closes, and ideally with at least 30-60 minutes of margin in case of slowdowns.
To estimate whether your backup fits in your window, you need three things: how much data moves per run (full vs incremental, plus compression), your effective throughput (the slowest link in the chain), and your available window hours. The Backup Time & Window Calculator does this calculation automatically and flags whether your current setup fits, runs tight, or overruns. With practical recommendations if it doesn't fit.
The most common mistakes in backup window planning:
- Using vendor speed specs instead of real-world throughput. A "1 Gbps" NAS doesn't actually write at 125 MB/s sustained. Plan for 90-115 MB/s depending on RAID level, drive age, and protocol overhead.
- Not accounting for compression overhead on weak CPUs. Enabling compression on a NAS with a low-power ARM CPU can actually slow backups down if the CPU can't compress data as fast as it can be transferred. Measure both ways before committing.
- Scheduling full backups nightly on large datasets. A 6 TB dataset doesn't fit in an overnight window on 1GbE. It takes 15+ hours. Switch to weekly full + nightly incremental.
- Forgetting that backup windows change. A backup that fits comfortably in a window today won't fit in two years when your dataset has doubled. Build headroom into your planning.
When Cloud Backup Makes Sense for Australian NAS Owners
Despite the upload speed constraints, cloud backup remains worthwhile for many Australian NAS owners. The key is understanding which part of the 3-2-1 backup strategy it serves. Cloud backup is best used as the offsite copy, not as the primary backup destination.
Cloud backup works well when: Your dataset is under 1 TB, your daily change rate is small, you're on NBN 100 or NBN 250, or you've seeded the initial backup locally. In these cases, nightly incremental backups complete in a reasonable window and the offsite coverage is genuine.
Cloud backup is impractical when: Your dataset is 4 TB or larger, you're on NBN 50 or slower, or you need fast recovery time objectives. Cloud restore time depends on download throughput, provider retrieval performance and any throttling; on asymmetric NBN services it will not generally equal the upload time. For large datasets, a local NAS-to-NAS backup (to a second NAS at a relative's house or office) is often more practical for Australian conditions than cloud.
Australian cloud storage options worth considering include Backblaze B2 (cost-effective for large datasets, Synology Hyper Backup compatible), Wasabi (no egress charge within its free-egress policy, which generally limits monthly egress to the active storage volume), and Amazon S3 (via Synology or QNAP native integration, but egress costs add up on large restores). Cloudflare R2 does not charge for direct internet egress, although storage, operations and Infrequent Access retrieval may still be billed. For any cloud backup, calculate your restore time as carefully as your backup time. The backup is only half the equation.
Backup Window Strategies That Actually Work
If you're struggling to fit your backup into a window, these strategies. Roughly in order of impact. Are worth considering:
- Switch from full to incremental nightly. This is usually the single biggest improvement available. A 5% daily change rate on a 4 TB dataset means 200 GB moves nightly instead of 4 TB. A 20× reduction in transfer volume.
- Run full backups weekly, not daily. Schedule the full backup for Saturday night when you have the whole weekend. Use incrementals Mon-Fri.
- Enable compression if your NAS has a capable CPU. Intel Celeron J-series and above handle AES-NI and compression well. Realtek and Marvell ARM CPUs are slower. Test before enabling compression in production.
- Upgrade your network if you're on 1GbE and backing up 8 TB or more. 2.5GbE can raise the network ceiling, but actual throughput depends on compatible NICs at both ends, the switch and cabling, NAS driver support and storage performance; 250 MB/s is not guaranteed. 10GbE is faster still. See our 10GbE networking guide for NAS for AU pricing and compatibility.
- Use a NAS-to-NAS offsite strategy for large datasets. A second NAS at a relative's home, connected over NBN, handles initial seed via physical transport and then runs incrementals overnight. This sidesteps the NBN upload limitation for the initial seed and keeps restore times fast.
- Stagger your backup jobs. If you're backing up to two destinations (local + cloud), don't run them simultaneously. They'll compete for disk I/O and network. Run local backup 10 PM-4 AM, cloud incremental 4 AM-7 AM.
Model your specific backup setup. Enter your dataset size, connection speed, and backup window to get realistic time estimates and window-fit analysis.
Related reading: our NAS buyer's guide.
See also: our complete Synology NAS Australia guide.
See also: our full Backup and Disaster Recovery guide.
How long does it take to back up 1 TB on a home NAS?
Over a 1GbE home network at real-world speeds (~110 MB/s sustained), a full backup of 1 TB takes approximately 2.5 hours. On a 50/20 NBN service, 1 TB takes at least about 111 hours at the full 20 Mbps upload cap, before protocol and backup overhead. As an illustration, 50 GB takes around eight minutes at 110 MB/s; on a 50/20 NBN service it takes at least about 5.6 hours at the full 20 Mbps upload cap, before overhead.
Will my backup finish overnight?
It depends on your dataset size, backup type, and connection speed. A full backup of 4 TB takes about 10 hours on 1GbE. Tight but usually fits in an overnight window. A nightly incremental for that same dataset (assuming 5% daily change, ~200 GB) takes about 30 minutes. On a 50/20 NBN service, a 200 GB incremental takes at least about 22.2 hours at the full upload cap, before overhead, so it will not fit a standard overnight window. The Backup Time & Window Calculator gives you specific numbers for your setup and flags whether your backup fits, runs tight, or overruns.
Why is my NAS backup so slow?
Common causes include: (1) you're backing up over NBN upload instead of LAN. NBN is typically 20-25× slower than a 1GbE local network; (2) you're running a full backup every night on a large dataset. Switch to weekly full + nightly incremental; (3) your destination drive is the bottleneck (older HDD or slow USB drive); (4) you've enabled compression on a NAS with a weak CPU, which adds CPU overhead faster than it saves transfer time; (5) backup software overhead. Some tools add significant overhead per-file, making them slow on datasets with millions of small files even if disk speeds are fine.
What's the difference between incremental and differential backups for NAS?
An incremental backup copies only what changed since the last backup. Whether that was a full or another incremental. Each run is small and fast, but restoration requires the last full plus every incremental since. A differential backup copies everything changed since the last full backup. Each run grows until the next full, but restoration only requires the last full plus one differential. For most home NAS users, incremental is the right choice: smaller daily transfers, and modern backup software (Hyper Backup, Active Backup for Business) handles the multi-file restoration automatically.
Can I speed up the initial full backup to the cloud?
Yes. Use a local seed strategy. Back up your data to a portable USB drive or external HDD, then ship or physically carry that drive to the cloud provider's ingestion facility. Some providers offer provider-supplied transfer appliances or another documented offline-ingest process; eligibility, region, cost and supported media vary. After ingestion, the cloud backup switches to incremental-only sync over NBN, which is far more manageable. If your provider doesn't offer seed import, an alternative is to do the initial backup locally to a NAS at an offsite location (a relative's home), then transition to remote incremental sync once the seed is complete.
Does Synology Hyper Backup or QNAP Hybrid Backup Sync support incremental backups?
Yes, both do. Synology Hyper Backup performs an initial full backup and then block-level incremental runs on its configured schedule; its rotation settings manage retained versions rather than scheduling a new full transfer each week. QNAP Hybrid Backup Sync similarly supports mixed schedules. Both tools also support compression and encryption, though you should test the performance impact of compression on your specific NAS model before enabling it in production. For a Synology setup guide including backup configuration, see the linked article.
How does Australian Consumer Law affect NAS purchases for backup use?
Australian Consumer Law provides statutory warranty protections beyond the manufacturer's stated warranty period. Australian Consumer Law does not set a fixed protection period for NAS devices; reasonable durability depends on factors including the product, price, quality, representations, maintenance and intended use. This applies when purchasing from Australian retailers (Mwave, PLE, Scorptec, Umart). If a failure means the NAS did not meet an applicable consumer guarantee, a remedy may be available even after the manufacturer's warranty expires; entitlement and the remedy depend on the circumstances and whether the failure is major or minor. This is relevant for backup use because NAS units running 24/7 may develop faults earlier than expected. And ACL protections provide recourse even if the hardware warranty has expired.