I've observed a similar horror when upgrading a cluster from Luminous to
Nautilus, which had the same effect of an overwhelming amount of
snaptrim making the cluster unusable.
In our case, we held its hand by setting all OSDs to have zero max
trimming PGs, unsetting nosnaptrim, and then slowly enabling snaptrim a
few OSDs at a time. It was painful to babysit but it allowed the
cluster to catch up without falling over.
On 2023-01-28 19:43, Victor Rodriguez wrote:
After some investigation this is what I'm seeing:
- OSD processes get stuck at least at 100% CPU if I ceph osd unset
nosnaptrim. They keep at 100% CPU even if I ceph osd set nosnaptrim.
They stayed like that for at least 26 hours. Some quick benchmarks
don't show a reduction of the performance of the cluster.
- Restarting a OSD lowers it's CPU usage to typical levels, as
expected, but it also usually sets some other OSD in a different host
to typical levels.
- All OSDs in this cluster take quite a bit to start: between 35 to 70
seconds depending on the OSD. Clearly much longer than any other OSD in
any of my clusters.
- I believe that the size of the rocksdb database is dumped in the OSD
log when an automatic compact operation is triggered. The "sum" sizes
of these OSD range between 2.5 and 5.1 GB. Thats way bigger that those
in any other cluster I have.
- ceph daemon osd.* calc_objectstore_db_histogram is giving values for
num_pgmeta_omap (I don't know what it is) way bigger than those on any
other of my clusters for some OSD. Also, values are not similar among
the OSD which hold the same PGs.
osd.0: "num_pgmeta_omap": 17526766,
osd.1: "num_pgmeta_omap": 2653379,
osd.2: "num_pgmeta_omap": 12358703,
osd.3: "num_pgmeta_omap": 6404975,
osd.6: "num_pgmeta_omap": 19845318,
osd.7: "num_pgmeta_omap": 6043083,
osd.12: "num_pgmeta_omap": 18666776,
osd.13: "num_pgmeta_omap": 615846,
osd.14: "num_pgmeta_omap": 13190188,
- Compacting the OSD barely reduces rocksdb size and does not reduce
num_pgmeta_omap at all.
- This is the only cluster I have were there are some RBD images that I
mount directly from some clients, that is, they are not disks for
QEMU/Proxmox VMs. Maybe I have something misconfigured related to
this? This cluster is at least two and half years old an never had
this issue with snaptrims.
Thanks in advance!
On 1/27/23 17:29, Victor Rodriguez wrote:
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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