[SOLVED] High I/O delay


New Member
Jun 9, 2023
I've recently set up a few LXC's on my PVE. I've noticed peaks of I/O delay about 30%, and sometimes 50%.
The PVE runs on a M.2 SSD NVE and also it havs a mechanical one attached. The HDD is a Seagate IronWolf.

One LXC has an SMB server, whereas the other LXC has qBittorrent that saves the downloads, via mounting point, in the SMB LXC.

Both LXC are hosted in the M.2, but the SMB also has the mechanical disk attached that shares.

Here I attach some screenshots with graphs.
qbittorrent LXC

This mechanical disk is supposed to handle this speeds without reaching its limit.
I'can't figure out what is wrong with my setup.
I've tried changing the disk to LVM and got the same results...
Hope someone can help.
So if I understand this right, the LXCs are using your host NVMe for booting and runtime but one has an SMB share to the other but why not just let the containers both share the drive?

I feel like this might be increasing I/O delay. Other things that increase I/O delay are:

* Any level of disk cache. Write back, write through, etc.
* SSD Emulation being checked (Check Discard for TRIM support)
* Huge amounts of IOPs on your VMs. For example, I have servers stored on two separate SSDs but when one is doing a massive update, IO delay can reach around 10% for that ONE server doing ONE update.

Also, HDDs are SLOW. So if two LXCs are writing to the same HDD of course it's going to have huge IO delay.

My suggestion: Put more HDDs together in a raid, or use another SSD for "caching" and the HDD for archival.
Thank you for your suggestion, I ended up setting a TrueNAS VM with HDD passthrough instead of an SMB LXC and all worked as expected.
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