Slow NAS in an architecture practice: diagnose Revit, Archicad and storage before investing

When a practice chooses a NAS, it generally compares capacity, the number of bays and price. A model providing 40 TB of usable space seems more than sufficient for fifteen people. But capacity says almost nothing about responsiveness.

A practice's data is varied: RVT and PLN models, DWG drawings, IFC exports, point clouds, textures, renders and site photographs. Some uses transfer large files; others involve many small reads and writes, often simultaneously. A NAS that is ideal for archiving can therefore be unsuitable for day-to-day work on collaborative models.

These indicators must be interpreted together. A NAS that can copy a file at 500 MB/s can still be slow with an application performing thousands of small operations that depend on one another.

Excellent copy throughput does not guarantee good application performance.

Hard disks or SSDs

A mechanical disk must physically move its read heads; an SSD accesses data electronically. With random access, the difference is considerable.

These are orders of magnitude, not guaranteed NAS performance: the controller, protocol, cache and parallelism change the results.

Replacing every disk with an SSD is not necessary. A two-tier architecture is often more rational: an SSD volume for active projects, HDDs for archives, and a backup on separate media. Before buying SSDs, check that the disks really are the bottleneck and, for Revit, that the new location remains compatible with the worksharing workflow.

RAID 5, RAID 6 or RAID 10

The RAID level mainly affects writes. The simplified "write penalty" model indicates how many physical operations a small random write costs.

For example, eight HDDs at around 100 IOPS each provide, in RAID 6, roughly (8 × 100) ÷ 6 ≈ 130 IOPS for small random writes. The same disks in RAID 10 would provide around 400. This calculation ignores caches and the controller, but it explains why two NAS units with identical disks can respond so differently.

During the rebuild following a disk failure, performance falls noticeably, sometimes for hours or even days with high-capacity disks. Monitoring must immediately report any degraded volume.

RAID is not a backup. It does not protect against deletion, ransomware, logical corruption or the loss of the NAS itself.

A NAS with eight fast disks but connected to the switch through a single 1 GbE link shares that link between all users.

These ceilings are theoretical: in practice, a 1 GbE link tops out at around 110 to 118 MB/s over SMB. In a twenty-person practice, it quickly becomes saturated when several people open large projects at the same time.

That does not mean the whole practice needs 10 GbE. A common, effective architecture combines workstations on 1 or 2.5 GbE with a 10 GbE link between the NAS and the main switch.

Keep two limitations in mind:

• If the NAS disks are already saturated, more bandwidth will change nothing.
• Throughput and latency are different things: a 10 Gbit/s fibre connection at home is still incompatible with Revit file-based worksharing.

Measure actual interface utilisation during busy periods before investing.

Revit does not simply open a file. In file-based worksharing, each person works on a local copy that constantly exchanges data with the central model, even outside synchronisations. Storage must therefore respond quickly and behave exactly like a Windows file server.

A NAS must emulate Windows perfectly

Autodesk states that Revit is designed for Windows and its file system. A third-party storage solution works if it correctly emulates Windows networking protocols; if it cannot, responsibility lies with its manufacturer. Before any investment, Autodesk recommends checking with the manufacturer that SMB is fully supported and what support is offered if a problem arises between SMB and the application.

In practice, a Synology or QNAP can host a central model, without a guarantee. If there are synchronisation errors or slowdowns, comparing it with a Windows file server can isolate the NAS.

Autodesk also documents a specific avenue when SMB incompatibility occurs: change the Worksharing Update Frequency from 5 seconds, its default value, to Manual. Exchanges between workstations and the server are reduced accordingly.

Latency: the absolute limit

According to Autodesk, file-based worksharing was designed for a local network, with latency in the region of 0 to 2 ms. Above that, timeouts, failed operations and central-model corruption become more likely.

VPN: an unsupported workflow

Autodesk describes file-based worksharing across a VPN as an unsupported workflow that can corrupt data during synchronisation. A fast home fibre connection makes no difference: latency, rather than throughput, is the problem.

The alternatives designed for remote work

• Revit Server: server-based worksharing, designed for teams spread across multiple sites over a WAN. It communicates over TCP rather than SMB.
• Revit Cloud Worksharing: central models hosted in the Autodesk cloud (Autodesk Docs), generally through an Autodesk BIM Collaborate Pro subscription.
• Remote desktop to a workstation in the office: only the display travels across the VPN; the model stays on the local network. Secure it (MFA, gateway) and validate it against the licensing conditions.

A NAS can be excellent for the practice's documents while being unsuitable for Revit worksharing.

Antivirus and EDR software inspects files when they are opened, modified and saved. That is essential, but it can introduce delays or locks that are incompatible with certain Revit operations. Autodesk even notes that antivirus software can lock files or slow transfers enough to simulate a shortage of memory.

When saving or synchronising with the central model fails, Autodesk asks you to check that security software is not blocking these file types:

Autodesk also publishes a broader list of possible exclusions: installation folders, AppData\Local\Autodesk, .rfa, .rte and .dwg file types, and others.

Confirming the hypothesis

Look for a correlation between slowdowns and security-agent activity: EDR logs, "sharing violation" errors in Revit journals, or Process Monitor traces showing antivirus activity on files at the moment they are saved.

Exclusions: yes, but methodically

An overly broad exclusion creates a security gap. Work with your security vendor to define targeted exclusions (central-model paths, the Revit.exe process), documented and reassessed regularly.

Disabling protection on a workstation or NAS to make Revit faster is not an acceptable optimisation.

By default, Revit creates local copies in the user's Documents folder. However, this folder is often redirected to a server by GPO or synchronised with OneDrive (Known Folder Move). As a result, a workstation with an NVMe SSD can be working on a local copy that is actually passing through the network or a synchronisation client.

Points to check:

• The actual location of local files (Options > File Locations > default path for user files).
• The absence of redirection or cloud synchronisation on that folder.
• Free space and the location of the temporary folder.
• Any antivirus or backup-client activity on these files.

The decisive test: on a diagnostic copy, without touching the production central model, place the working files in a non-synchronised local SSD folder (for example, C:\RevitLocal). A clear difference in opening or synchronisation time points to profiles, redirection or synchronisation as the cause.

For Archicad, distinguish document storage from Teamwork collaboration through BIMcloud. BIMcloud is a server application with its own components (BIMcloud Manager, BIMcloud Server, Delta Cache), rather than a simple SMB share. A NAS that performs well with DWG files or archives is therefore not automatically a good BIMcloud server.

Graphisoft's memory recommendations by practice size:

Graphisoft recommends dedicated hardware. For the BIMcloud Server component, the vendor requires at least 100 GB of free space beyond the hosted project data and emphasises that storage speed is critical. It also offers a more detailed RAM calculation: 2 GB plus 1.5 times the size of projects used simultaneously, bearing in mind that an active project occupies around 4.5 times the size of its PLN file.

When BIMcloud slows down, measure the resources of the BIMcloud server itself (RAM, CPU, disk latency) and identify the scope: all users, one project, or only remote colleagues? An undersized server will remain slow even after an upgrade to 10 GbE.

SMB (Server Message Block) is the protocol used for Windows file shares. Its version and security options directly affect exchanges with a NAS.

Check the negotiated dialect

From a workstation connected to the share, in PowerShell:

Get-SmbConnection | Select-Object ServerName, ShareName, Dialect, NumOpens

Windows 11 24H2: SMB signing becomes mandatory

Since Windows 11 24H2, SMB signing has been required by default for all outbound connections. Previously, Windows only required it for domain controllers' SYSVOL and NETLOGON shares. Microsoft recommends enabling signing on the NAS rather than disabling it on workstations.

The practical consequence: after workstations migrate to 24H2, the NAS must sign every exchange, placing a load on its processor. If the slowdowns appeared after this update, it is a serious lead. The right response is up-to-date firmware or a more capable NAS, rather than disabling the protection.

Encryption and SMB Multichannel

SMB encryption protects the confidentiality of exchanges but places more load on the server's processor. SMB Multichannel can use several network links in parallel if the client and server support it; it will not, however, speed up storage that is limited by its disks.

A good SMB diagnosis checks the mechanisms actually in use; it does not disable protections to gain a few percentage points.

A practice's NAS rarely does nothing but share files: backups, snapshots, replication to a second site, cloud synchronisation, indexing, data-integrity checks (data scrubbing), antivirus scans and RAID rebuilds. These tasks are useful, but they compete with users' accesses, particularly on HDDs.

Illustrative scenario: a fourteen-person practice

A fictional scenario, based on a plausible configuration to illustrate the method. The figures are indicative.

The practice has recent workstations, a NAS with eight HDDs in RAID 6 and a Gigabit network. Every morning between 9 and 10 am, opening a reference model takes around 3 minutes, compared with less than a minute in the afternoon.

The measurements taken while the symptom occurs show:

• NAS disks close to 100% activity, with high write latency;
• a network link that is far from saturated;
• workstations without processor or memory saturation;
• a backup with integrity verification that starts every day at 8:45 am.

The task is moved to the evening, while retaining a daily backup. Measured after the change, the same model opens in around 55 seconds in the morning. The correction costs zero francs, and provides measured evidence of the cause.

The point of a diagnosis is not to guess the cause, but to demonstrate which component actually limits the work.

iperf3: isolate the network

On a test machine placed on the server side:

iperf3 -s

From a workstation:

iperf3 -c 192.168.1.10 -t 30

On 1 GbE, a result around 940 Mbit/s indicates a healthy link. Much less points to cabling, speed negotiation or a switch to check. If the NAS cannot run iperf3, use a dedicated machine connected to the same switch.

Process Monitor

Use this Microsoft Sysinternals tool filtered on Revit.exe and the central-model path. It helps identify:

• the paths actually used;
• repeated accesses to the same files;
• locks (SHARING VIOLATION);
• third-party processes intervening (antivirus, backup);
• unusually long operations.

Traces can contain sensitive data and grow very quickly: collection must be short and targeted.

Revit journals

%LOCALAPPDATA%\Autodesk\Revit\Autodesk Revit 2025\Journals

Replace 2025 with your version. Compare the journals of two workstations, or two openings of the same project, to identify the step that is slowing down.

Do not confuse the measurements

• A good iperf3 result does not prove that the NAS is fast.
• A processor at 20% does not rule out a single saturated core: many Revit operations are single-threaded.
• A disk at 100% activity does not, on its own, prove that it needs replacing.

Only cross-checked measurements, taken while the symptom occurs, allow a reliable diagnosis.

Take a fictional practice with twelve people who each lose fifteen minutes a day to avoidable IT waiting, across twenty working days:

12 × 15 min × 20 days = 60 hours per month.

At an illustrative fully loaded hourly cost of CHF 75, that represents CHF 4,500 of working capacity tied up per month, or around CHF 54,000 per year.

This is not a net loss: some waiting time is reused, and not all recovered time becomes revenue. But the order of magnitude is enough to inform an investment decision.

Before signing a CHF 15,000 quotation

If storage is genuinely saturated, replacing the NAS, the disks and part of the network may be justified. If the cause is antivirus software, a poorly scheduled backup, a poorly structured model or a VPN, new hardware will solve nothing.

Before replacing your infrastructure, measure what is actually slowing down your practice.

Request a performance diagnosis from Sunitech

The right choice depends first on the collaboration model.

A NAS remains an excellent investment when it meets a clearly identified use: documents, archives and compatible production data. It is not a universal server capable of replacing every BIM collaboration solution.

At Sunitech, we support SMEs in Geneva, Lausanne, Vaud and throughout French-speaking Switzerland in managing, securing and developing their IT. For architecture practices, we work across the entire chain:

• Performance diagnosis: workstations, network, NAS, SMB, antivirus and Revit or Archicad workflows, with a measured before/after report.
• Architecture and sizing: storage, Windows file server, Revit Server, BIMcloud and hybrid architectures.
• Backup and continuity: backup strategy, restoration tests and ransomware protection.
• Managed IT: monitoring, updates and equipment maintenance.

When a problem relates to modelling (Revit families, Archicad project structure), we work with your BIM manager: an IT configuration and a poorly optimised model cannot be corrected in the same way.

Are your architects waiting for Revit or Archicad? Contact Sunitech

A NAS can report a perfectly normal status while holding back an entire team. Healthy disks do not guarantee adequate response times, a 10 GbE link does not solve a latency problem, and a new server cannot compensate for misconfigured antivirus software or an unsupported collaboration workflow.

An architecture practice's performance depends on coherence between workstations, network, storage, software and working methods.

Before replacing your NAS, ask your IT provider to show you what is actually slowing down your colleagues. Not a hypothesis, not a sales argument: measurements.