Re: Constant write load on 4 node ceph cluster

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Is the storage being used for the whole VM disk?

If so have you checked none of your software is writing constant log's? Or something that could continuously write to disk.

If your running a new version you can use : https://docs.ceph.com/docs/mimic/mgr/iostat/ to locate the exact RBD image.


---- On Mon, 14 Oct 2019 20:32:53 +0800 Ingo Schmidt <i.schmidt@xxxxxxxxxxx> wrote ----

Hi all

We have a 4 node ceph cluster that runs generally fine. It is the storage backend for our virtualization cluster with Proxmox, that runs about 40 virtual machines (80% various Linux Servers). Now that we have implemented monitoring, i see that there is a quite constant write load of about 4-10MB/s throughout the whole day and even weekends, while read load clearly is bound to daily work hours.
I am wondering whats up with this. Is this normal?
Outside working hours, there is almost no read load, well under 1MB/s, while write Load stays relatively constant at around 5MB/s. During rebalancing of the Cluster, normal write load decreases significantly to under 1MB/s. Overall performance is not greatly affected by rebalancing as it is tuned to relatively slow backfills (osd_max_backfills = '3' | osd_recovery_max_active = '3')
After rebalance has been finished, the average write load of about 5MB/s reappears.
I have attached a little screenshot for reference.


Can someone shed a little light on this?
Thanks.

kind regards
Ingo Schmidt


IT-Department
Island Municipality Langeoog
with in-house operations
Tourismusservice and Schiffahrt

Hauptstraße 28
26465 Langeoog
Deutschland

[ http://www.langeoog.de/ ]
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