CAX tools

TrueNAS SCALE · SMB · Windows

Slow SMB folders on TrueNAS

The folder opens instantly in the TrueNAS shell, but Explorer takes minutes. Usually the NAS isn't the problem.

Try this first

Sort by Date modified, not Date

Date and Date modified are different columns. For photos and videos, Date means “date taken”, so Explorer has to open every file over the network before it can sort.

Click the Name or Date modified header. If the folder is suddenly fast, you're done.

Raw listing0.9 s
Sorted by Date≈120 s
By Date modified≈1 s

Still slow? Work through these in order.

Step 1

Find where the time goes

Fill these in and every command on the page updates. They're only stored in your browser.

1. Time a raw listing

Run this in PowerShell on the PC. It lists the folder without thumbnails or sorting.

PowerShell
Measure-Command { Get-ChildItem '' | Out-Null }

Check it actually read the folder — this should print roughly the number of files you expect. A red “Cannot find path” means the path is wrong.

PowerShell
(Get-ChildItem '').Count
A few seconds or lessNAS and network are fine → Step 2 Still slowNetwork or dataset problem → Step 3
Step 2

Fix Explorer

Some columns force Explorer to open every file. Avoid them on network folders.

  1. Sort by a fast column. Name, Date modified, Size or Type. Right-click a header and untick Date so you don't click it by accident.
  2. Turn off grouping. View → Group by → (None).
  3. Stop the photo/video template. Right-click the folder → Properties → Customize → Optimize for General items, and tick apply to all subfolders.
  4. Turn off thumbnails on network folders only. Local folders keep theirs. The last line restarts Explorer (the taskbar blinks).
    PowerShell
    $key = 'HKCU:\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer'
New-Item -Path $key -Force | Out-Null
Set-ItemProperty -Path $key -Name DisableThumbnailsOnNetworkFolders -Value 1 -Type DWord
Stop-Process -Name explorer -Force
  5. Make it the default. View → Options → View → Apply to Folders.
Which columns are slow?
ColumnComes from
Name, Date modified, SizeThe file listfast
TypeFile extension, looked up locallyfast
Date, Date taken, Media createdInside each photo/videoslow
Dimensions, Length, Bit rateInside each media fileslow
Rating, Tags, Title, AuthorsMetadata inside the fileslow

Need to sort by date taken? There's no fast way over SMB. Use a photo manager with its own index, or a media app on the NAS.

Step 3

If the raw listing is slow too

Opening a folder takes thousands of tiny requests, so delay matters far more than bandwidth. Open whichever check fits.

Traffic goes through a VPN

Check which adapter the PC uses to reach the NAS. You want Ethernet or Wi-Fi.

PowerShell
Find-NetRoute -RemoteIPAddress  | Select-Object -First 1 InterfaceAlias

If it names a VPN:

  • Tailscale — untick Use Tailscale subnets on PCs that stay home.
  • ZeroTier — turn off Allow Managed Routes.
  • Other VPNs — enable Allow LAN access / split tunneling, or disconnect at home.
The NAS name points to the wrong address
PowerShell
Resolve-DnsName  | Select-Object Name, IPAddress

A 100.x.x.x (Tailscale), public or unfamiliar IPv6 address is a problem. Try opening \\\share by IP instead and compare.

Lag or lost packets
PowerShell
ping -n 20

Wired should be <1ms, Wi-Fi a few ms. Jumpy times or Request timed out mean weak Wi-Fi, a bad cable or switch.

PowerShell
Get-NetAdapter | Select-Object Name, Status, LinkSpeed

100 Mbps on a gigabit network usually means a damaged cable or port.

Old SMB version or encryption

Open a folder on the share, then run PowerShell as administrator:

PowerShell (admin)
Get-SmbConnection | Select-Object ServerName, ShareName, Dialect, Signed, Encrypted

Dialect should be 3.1.1 or 3.0. Anything older: turn off SMB1 in TrueNAS's SMB service. Encrypted: True can slow a low-power NAS.

Dataset settings

In the TrueNAS shell (System → Shell):

TrueNAS shell
zfs get casesensitivity,xattr,atime
casesensitivitywant insensitive. Can only be set at creation — make a new dataset with the SMB preset and copy the data over. xattrwant sa. Safe to change. atimewant off. Safe to change.
TrueNAS shell
zfs set xattr=sa 
zfs set atime=off

Don't share the pool's root dataset directly — make a child dataset with the SMB preset.

The NAS is busy, low on RAM or nearly full

Fast the second time? The NAS is forgetting folder info between visits. More RAM helps most.

Scrub, resilver or heavy disk use?

TrueNAS shell
zpool status | grep -E 'pool:|scan:'
zpool iostat -v 2

Nearly full? ZFS slows down above ~80% CAP, a lot above 90%.

TrueNAS shell
zpool list -o name,size,alloc,free,cap,frag
Huge folders · tens of thousands of files

These stay slow over SMB even when everything is right. Split them into subfolders, by year or first letter.

Still slow

See what Explorer is opening

Run this on the NAS while you open the folder:

TrueNAS shell
watch -n1 'smbstatus -L | tail -25'
What the list tells you
  • Photos/videos — something still reads metadata. Recheck sort, Group by and media columns.
  • .exe / .lnk — icon extraction. Normal, but slow in folders full of programs.
  • Codec packs (K-Lite, Icaros) read more of each file.
  • Antivirus scanning network files — exclude the share if you're allowed.
  • Sync/backup apps (OneDrive, Dropbox, …) watching the share — pause and retest.
  • Offline Files — Control Panel → Sync Center → Manage offline files.
  • Shell extensions (archive tools, Git clients) — test in another file manager or a fresh Windows user.

On a Mac: turn on Apple SMB2/3 Protocol Extensions in TrueNAS and use List view sorted by Name.