Re: nvme SSD and poor performance
Pierre Willaime wrote:
> Hi,
>
> I have a nvme SSD (CAZ-82512-Q11 NVMe LITEON 512GB) on debian stable
> (bulleye now).
>
> For a long time, I suffer poor I/O performances which slow down a lot of
> tasks (apt upgrade when unpacking for example).
>
> I am now trying to fix this issue.
The first question is, how slow is this storage?
Here is a good article on using fio:
https://arstechnica.com/gadgets/2020/02/how-fast-are-your-disks-find-out-the-open-source-way-with-fio/
> Using fstrim seems to restore speed. There are always many GiB which are
> reduced :
>
> # fstrim -v /
> / : 236,7 GiB (254122389504 octets) réduits
>
> then, directly after :
>
> # fstrim -v /
> / : 0 B (0 octets) réduits
That's normal.
> but few minutes later, there are already 1.2 Gib to trim again :
>
> # fstrim -v /
> / : 1,2 GiB (1235369984 octets) réduits
That's high but not impossible.
> /Is it a good idea to trim, if yes how (and how often)?/
I trim in a cron job once per week on high activity systems and
once per month on lower activity systems.
> I also noticed many I/O access from jbd2 and kworker such as :
>
> # iotop -bktoqqq -d .5
> 11:11:16 364 be/3 root 0.00 K/s 7.69 K/s 0.00 % 23.64 %
> [jbd2/nvme0n1p2-]
> 11:11:16 8 be/4 root 0.00 K/s 0.00 K/s 0.00 % 25.52 %
> [kworker/u32:0-flush-259:0]
>
> The percentage given by iotop (time the thread/process spent while swapping
> in and while waiting on I/O) is often high.
These are the kernel processes responsible for writing to disk.
> I added the "noatime" option to /etc/fstab / line but it does not seem to
> reduce the number of access.
It does, but not much more than the Debian default.
Test your drive's speed, then come back with the results.
-dsr-
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