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Could someone either point me at a good explanation about how volume actual size and size limit work when snapshots exist? To elaborate, I noticed that the snapshot size is counted towards actual size. When I delete a snapshot, the actual size goes down. Sometimes, I see a volume actual size can be larger than the volume size limit. Ive seen applications write data to that volume without a problem with the actual size growing well beyond the size limit. while another time I had an application crash because the size limit was reached. This makes it confusing for me to determine when a volume is actually really about to grow beyond its real hard size limit (ie, app going to crash or denied write action), or to determine how much is actually really still free, even though the actual size is showing larger than the volume size limit. |
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Replies: 1 comment 3 replies
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Did you mean https://longhorn.io/docs/1.7.2/references/settings/#snapshot-maximum-count? |
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Thanks, but no I do not mean maximum snapshot count. I mean for example, when I create a volume of 10 GB and there is 1GB of application data stored into it, lets say I make a snapshot every hour. The application changes 100 MB on average every hour. So after 10 hours I will have 1GB of snapshot data on top of the 1GB actual data. The volume actual size will show as 2GB even though there is only 1GB of actual application data. The other 1GB is in 10 snapshots. When I start deleting the snapshots 1 at a time, I can see the actual size coming down by 100MB with each snapshot. At least, this is how I think it works from the behavior I have seen by making and deleting snapshots. So the question is, when I look at the volumes in Longhorn it is not obvious how much the actual data is, and how much of it is snapshot data. Given the example above, is there a way to see this somehwere? |
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Currently, Longhorn actual size is the sum the sizes of volume head (active data) and snapshots. We can improve this. For now, you can get the statistics by https://longhorn.io/docs/1.7.2/monitoring/kubelet-volume-metrics/. |
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Thank you. I am using Prometheus and Grafana, I can see those metrics. Don't mind me asking but just to be absolutely clear and so that I can trust this: And as a sidenote: |
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Currently, Longhorn actual size is the sum the sizes of volume head (active data) and snapshots. We can improve this.
https://longhorn.io/docs/1.7.2/nodes-and-volumes/volumes/volume-size
For now, you can get the statistics by https://longhorn.io/docs/1.7.2/monitoring/kubelet-volume-metrics/.