Linux

In the sysstat package, there's a command, iostat, that shows the amount of time that the average CPU (core) is waiting for something.

avg-cpu:  %user   %nice %system %iowait  %steal   %idle
           0.57    0.01    0.55    3.14    0.00   95.73

"User" is the CPU time used by regular processes. "Nice" is the time used by "niced" processes, stuff running at low priority. "System" is time used by the kernel. "Iowait" is the time waiting for I/O operations to complete.

If you're bounded on I/O, then the iowait number is probably going to be relatively high.

It'll also show you I/O load on each device (and the sysstat package can log this over time, let you use sar to see historical numbers).

You can artificially induce load on a given I/O device to see whether load on it induces your problem. Something like this:

$ dd if=/dev/zero of=filename-that-you-want bs=1M

That'll start your system just writing zeroes to a file. If it's I/O contention on the mSATA drive, then I'd expect you to see the problems you mentioned.

One thing you might check is whether your system is logging errors during this time. I don't know what a failing SSD looks like, but in my experience a failing rotational drive would often see errors and then attempts to re-perform I/O operations. That produces seriously-degraded disk I/O performance. These errors will show up in the kernel log. To see kernel errors since the current boot:

$ journalctl -kb

The smartmontools package contains a command, smartctl, which will let you see what your drive thinks of its own health. I'm not really familiar with what a failing SSD would look like, but with rotational drives, it can indicate that something's wrong with the drive, and it looks like my SSDs do report SMART status.

# smartctl -a /dev/sda

Moving swap

Linux can, if it needs to, use a swap file instead of a swap partition, so you don't need to repartition your NVMe if you just want to try putting your swap on the NVMe.

If you want to, first, for the current boot, disable all the active swap partitions.

# swapoff -a

If you run top, you'll see the available swap be at zero.

Then you want to create the swap file. Say we drop it in /var:

# mkswap --file /var/swapfile --size 32GiB

And then you can enable it:

# swapon /var/swapfile

Then see how things perform.

If it makes your problem go away and you want to make the change persistent:

In /etc/fstab, you'll have a line for your swap partition that the system reads at each boot. Will probably look something like this:

/dev/mapper/system--vg-swap_1 none            swap    sw              0       0

Comment that out by sticking a "#" at the beginning of your line, and put a line in for your new swapfile on the NVMe:

/var/swapfile none            swap    sw              0       0