Re: Very slow snaptrim operations blocking client I/O

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Ah yes, checked that too. Monitors and OSD's report with ceph config show-with-defaults that bluefs_buffered_io is set to true as default setting (it isn't overriden somewere).


On 1/27/23 17:15, Wesley Dillingham wrote:
I hit this issue once on a nautilus cluster and changed the OSD parameter bluefs_buffered_io = true (was set at false). I believe the default of this parameter was switched from false to true in release 14.2.20, however, perhaps you could still check what your osds are configured with in regard to this config item.

Respectfully,

*Wes Dillingham*
wes@xxxxxxxxxxxxxxxxx
LinkedIn <http://www.linkedin.com/in/wesleydillingham>


On Fri, Jan 27, 2023 at 8:52 AM Victor Rodriguez <vrodriguez@xxxxxxxxxxxxx> wrote:

    Hello,

    Asking for help with an issue. Maybe someone has a clue about what's
    going on.

    Using ceph 15.2.17 on Proxmox 7.3. A big VM had a snapshot and I
    removed
    it. A bit later, nearly half of the PGs of the pool entered
    snaptrim and
    snaptrim_wait state, as expected. The problem is that such operations
    ran extremely slow and client I/O was nearly nothing, so all VMs
    in the
    cluster got stuck as they could not I/O to the storage. Taking and
    removing big snapshots is a normal operation that we do often and
    this
    is the first time I see this issue in any of my clusters.

    Disks are all Samsung PM1733 and network is 25G. It gives us
    plenty of
    performance for the use case and never had an issue with the hardware.

    Both disk I/O and network I/O was very low. Still, client I/O
    seemed to
    get queued forever. Disabling snaptrim (ceph osd set nosnaptrim)
    stops
    any active snaptrim operation and client I/O resumes back to normal.
    Enabling snaptrim again makes client I/O to almost halt again.

    I've been playing with some settings:

    ceph tell 'osd.*' injectargs '--osd-max-trimming-pgs 1'
    ceph tell 'osd.*' injectargs '--osd-snap-trim-sleep 30'
    ceph tell 'osd.*' injectargs '--osd-snap-trim-sleep-ssd 30'
    ceph tell 'osd.*' injectargs '--osd-pg-max-concurrent-snap-trims 1'

    None really seemed to help. Also tried restarting OSD services.

    This cluster was upgraded from 14.2.x to 15.2.17 a couple of
    months. Is
    there any setting that must be changed which may cause this problem?

    I have scheduled a maintenance window, what should I look for to
    diagnose this problem?

    Any help is very appreciated. Thanks in advance.

    Victor


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