76 lines
3.5 KiB
Markdown
76 lines
3.5 KiB
Markdown
[](https://app.fossa.com/projects/git%2Bgithub.com%2Fopenebs%2Frawfile-localpv?ref=badge_shield)
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RawFilePV
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===
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Kubernetes LocalPVs on Steroids
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Prerequisite
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---
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- Kubernetes: 1.21+
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Install
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---
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`helm install -n kube-system rawfile-csi ./deploy/charts/rawfile-csi/`
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Usage
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---
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Create a `StorageClass` with your desired options:
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```
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apiVersion: storage.k8s.io/v1
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kind: StorageClass
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metadata:
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name: my-sc
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provisioner: rawfile.csi.openebs.io
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reclaimPolicy: Delete
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volumeBindingMode: WaitForFirstConsumer
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allowVolumeExpansion: true
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```
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Features
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---
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- [x] Direct I/O: Near-zero disk performance overhead
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- [x] Dynamic provisioning
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- [x] Enforced volume size limit
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- [x] Access Modes
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- [x] ReadWriteOnce
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- ~~ReadOnlyMany~~
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- ~~ReadWriteMany~~
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- [ ] Volume modes
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- [x] `Filesystem` mode
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- [ ] `Block` mode
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- [x] Volume metrics
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- [x] Supports fsTypes: `ext4`, `btrfs`, `xfs`
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- [x] Online expansion: If fs supports it (e.g. ext4, btrfs, xfs)
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- [ ] Online shrinking: If fs supports it (e.g. btrfs)
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- [ ] Offline expansion/shrinking
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- [ ] Ephemeral inline volume
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- [x] Filesystem-level snapshots: `btrfs` supported
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Motivation
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---
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One might have a couple of reasons to consider using node-based (rather than network-based) storage solutions:
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- Performance: Almost no network-based storage solution can keep up with baremetal disk performance in terms of IOPS/latency/throughput combined. And you’d like to get the best out of the SSD you’ve got!
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- On-premise Environment: You might not be able to afford the cost of upgrading all your networking infrastructure, to get the best out of your network-based storage solution.
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- Complexity: Network-based solutions are distributed systems. And distributed systems are not easy! You might want to have a system that is easier to understand and to reason about. Also, with less complexity, you can fix unpredicted issues more easily.
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Using node-based storage has come a long way since k8s was born. Right now, OpenEBS’s hostPath makes it pretty easy to automatically provision hostPath PVs and use them in your workloads. There are known limitations though:
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- You can’t monitor volume usage: There are hacky workarounds to run “du” regularly, but that could prove to be a performance killer, since it could put a lot of burden on your CPU and cause your filesystem cache to fill up. Not really good for a production workload.
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- You can’t enforce hard limits on your volume’s size: Again, you can hack your way around it, with the same caveats.
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- You are stuck with whatever filesystem your kubelet node is offering
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- You can’t customize your filesystem:
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All these issues stem from the same root cause: hostPath/LocalPVs are simple bind-mounts from the host filesystem into the pod.
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The idea here is to use a single file as the block device, using Linux’s loop, and create a volume based on it. That way:
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- You can monitor volume usage by running df in `O(1)` since devices are mounted separately.
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- The size limit is enforced by the operating system, based on the backing file size.
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- Since volumes are backed by different files, each file could be formatted using different filesystems, and/or customized with different filesystem options.
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## License
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[](https://app.fossa.com/projects/git%2Bgithub.com%2Fopenebs%2Frawfile-localpv?ref=badge_large)
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