Uploading to pool suddenly extremely slow

TrueNAS General
1

I have no idea what’s going on or where to start troubleshooting.
Few days ago I noticed an automated backup when I start Windows taking weirdly long, namely the merging newer files into the main large full backup, and today acidentally realized something really is wrong: I can copy stuff from the NAS at the usual 115-ish MB/s, but copying anything there results in 5MB/s at most. There are no warnings or anything, everything claims to be healthy. Rebooting didn’t help.
The system is running version 13.3-U1.2.

I had zero problems until now.
Could anyone tell me where and how should I start troubleshooting? I am completely lost.

2

Have you got any quotas on your dataset that you are nearing? Also how full is the pool?

3

I have no idea what quotas is (english is not my native language), but the pool is 72% full and I occasionally make sure it doesn’t go above 80%, because I vaguely remember there are warnings about performance past a certain point.

The entire NAS is mostly a passive storage of backups and illicit content, no heavy writes.
I think the SSDs must be fine, but I might need to do some more advanced checks or something.

4

So you can assign quotas to datasets on your TrueNAS to stop the dataset consuming more space than desired. When you get close to this limit things can go very slow until the limit is reached.

Yes good idea to keep the pool below 80%. I presume you are accessing the NAS via an SMB share?

5

Ah ok.
No, this is an extremely simple setup that realistically only works as a static storage.

Yes I am accessing it mostly from Win10, so SMB. It worked just fine for years, but something happened somewhere in the recent days to weeks. Probably. I have no way to tell, unfortunately.
At least I have just confirmed it’s just as slow trying to copy something onto the NAS from my wife’s notebook, so it’s not something rotting on my PC.

6

I should also point out this is a virtualized TrueNAS running under ESXi for context, but again I had zero problems up until now. I just have no idea how to troubleshoot this.

7

If you could provide hardware specs and clarify how you have passed the disks through to the VM that would be good. Also any info from the system such as zpool status and zfs list.

8

Well WTF? I don’t understand anything anymore.
I rebooted the entire ESXi host, and now it works fine again.

However, the server has Supermicro X11 board, 32GB RAM, Xeon E-2136 or whatever, and a LSI HBA that’s passed through. I’d need more coffee to remember and dig up the specifics.

skladiste% zpool status
  pool: boot-pool
 state: ONLINE
status: Some supported and requested features are not enabled on the pool.
        The pool can still be used, but some features are unavailable.
action: Enable all features using 'zpool upgrade'. Once this is done,
        the pool may no longer be accessible by software that does not support
        the features. See zpool-features(7) for details.
  scan: scrub repaired 0B in 00:00:02 with 0 errors on Sat Sep 13 03:45:02 2025
config:

        NAME        STATE     READ WRITE CKSUM
        boot-pool   ONLINE       0     0     0
          da0p2     ONLINE       0     0     0

errors: No known data errors

  pool: skladiste
 state: ONLINE
  scan: scrub repaired 0B in 00:43:01 with 0 errors on Sat Sep 13 03:43:01 2025
config:

        NAME                                            STATE     READ WRITE CKSUM
        skladiste                                       ONLINE       0     0     0
          raidz1-0                                      ONLINE       0     0     0
            gptid/6ca9a162-8dfc-11ed-9bb9-005056a4f055  ONLINE       0     0     0
            gptid/6c9e9772-8dfc-11ed-9bb9-005056a4f055  ONLINE       0     0     0
            gptid/6ca7ec87-8dfc-11ed-9bb9-005056a4f055  ONLINE       0     0     0
            gptid/6ca0a7ee-8dfc-11ed-9bb9-005056a4f055  ONLINE       0     0     0

errors: No known data errors


skladiste% zfs list
NAME                                                         USED  AVAIL  REFER  MOUNTPOINT
boot-pool                                                   2.54G  12.5G    24K  none
boot-pool/.system                                            112M  12.5G    28K  legacy
boot-pool/.system/configs-4ac1284ebed34cc7a334eddc730c1ce2  91.4M  12.5G  91.4M  legacy
boot-pool/.system/cores                                       24K  1024M    24K  legacy
boot-pool/.system/rrd-4ac1284ebed34cc7a334eddc730c1ce2      14.4M  12.5G  14.4M  legacy
boot-pool/.system/samba4                                    1.52M  12.5G  93.5K  legacy
boot-pool/.system/services                                    24K  12.5G    24K  legacy
boot-pool/.system/syslog-4ac1284ebed34cc7a334eddc730c1ce2   4.29M  12.5G  4.29M  legacy
boot-pool/.system/webui                                       24K  12.5G    24K  legacy
boot-pool/ROOT                                              2.41G  12.5G    24K  none
boot-pool/ROOT/13.3-U1.2                                    2.41G  12.5G  1.25G  /
boot-pool/ROOT/Initial-Install                                 1K  12.5G  1.15G  legacy
boot-pool/ROOT/default                                       178K  12.5G  1.16G  legacy
skladiste                                                   3.56T  1.38T   337K  /mnt/skladiste
skladiste/install                                           57.2G  1.38T  57.2G  /mnt/skladiste/install
skladiste/media                                             3.12T  1.38T  3.12T  /mnt/skladiste/media
skladiste/users                                              395G  1.38T   291K  /mnt/skladiste/users
skladiste/users/martina                                      216G  1.38T   216G  /mnt/skladiste/users/martina
skladiste/users/octopuss                                     179G  1.38T   179G  /mnt/skladiste/users/octopuss
9

Could anyone tell me how do I upgrade the pool and what will that bring me?