In Kubernetes, using storage in the right way is well-facilitated by the API. However, unless you are running in a major public cloud, that API may not be hooked up to anything. This frequently sends users down a rabbit hole of researching all the various options for storage backends for their platform, for Kubernetes, and for their workloads. There are a lot of options out there, and it can be fairly bewildering.
For Talos, we try to limit the options somewhat to make the decision-making easier.
If you are running on a major public cloud, use their block storage. It is easy and automatic.
Sidero Labs recommends having separate disks (apart from the Talos install disk) to be used for storage.
Redundancy, scaling capabilities, reliability, speed, maintenance load, and ease of use are all factors you must consider when managing your own storage.
Running a storage cluster can be a very good choice when managing your own storage, and there are two projects we recommend, depending on your situation.
If you need vast amounts of storage composed of more than a dozen or so disks, we recommend you use Rook to manage Ceph. Also, if you need both mount-once and mount-many capabilities, Ceph is your answer. Ceph also bundles in an S3-compatible object store. The down side of Ceph is that there are a lot of moving parts.
Please note that most people should never use mount-many semantics. NFS is pervasive because it is old and easy, not because it is a good idea. While it may seem like a convenience at first, there are all manner of locking, performance, change control, and reliability concerns inherent in any mount-many situation, so we strongly recommend you avoid this method.
If your storage needs are small enough to not need Ceph, use Mayastor.
Ceph is the grandfather of open source storage clusters. It is big, has a lot of pieces, and will do just about anything. It scales better than almost any other system out there, open source or proprietary, being able to easily add and remove storage over time with no downtime, safely and easily. It comes bundled with RadosGW, an S3-compatible object store; CephFS, a NFS-like clustered filesystem; and RBD, a block storage system.
With the help of Rook, the vast majority of the complexity of Ceph is hidden away by a very robust operator, allowing you to control almost everything about your Ceph cluster from fairly simple Kubernetes CRDs.
So if Ceph is so great, why not use it for everything?
Ceph can be rather slow for small clusters. It relies heavily on CPUs and massive parallelisation to provide good cluster performance, so if you don’t have much of those dedicated to Ceph, it is not going to be well-optimised for you. Also, if your cluster is small, just running Ceph may eat up a significant amount of the resources you have available.
Troubleshooting Ceph can be difficult if you do not understand its architecture. There are lots of acronyms and the documentation assumes a fair level of knowledge. There are very good tools for inspection and debugging, but this is still frequently seen as a concern.
Mayastor is an OpenEBS project built in Rust utilising the modern NVMEoF system. (Despite the name, Mayastor does not require you to have NVME drives.) It is fast and lean but still cluster-oriented and cloud native. Unlike most of the other OpenEBS project, it is not built on the ancient iSCSI system.
Unlike Ceph, Mayastor is just a block store. It focuses on block storage and does it well. It is much less complicated to set up than Ceph, but you probably wouldn’t want to use it for more than a few dozen disks.
Mayastor is new, maybe too new. If you’re looking for something well-tested and battle-hardened, this is not it. However, if you’re looking for something lean, future-oriented, and simpler than Ceph, it might be a great choice.
To see a live demo of this section, see the video below:
Either during initial cluster creation or on running worker nodes, several machine config values should be edited.
(This information is gathered from the Mayastor documentation.)
We need to set the
vm.nr_hugepages sysctl and add
openebs.io/engine=mayastor labels to the nodes which are meant to be storage nodes.
This can be done with
talosctl patch machineconfig or via config patches during
talosctl gen config.
Some examples are shown below: modify as needed.
First create a config patch file named
mayastor-patch.yaml with the following contents:
- op: add path: /machine/sysctls value: vm.nr_hugepages: "1024" - op: add path: /machine/nodeLabels value: openebs.io/engine: mayastor
Using gen config
talosctl gen config my-cluster https://mycluster.local:6443 --config-patch @mayastor-patch.yaml
Patching an existing node
talosctl patch --mode=no-reboot machineconfig -n <node ip> --patch @mayastor-patch.yaml
Note: If you are adding/updating the
vm.nr_hugepageson a node which already had the
openebs.io/engine=mayastorlabel set, you’d need to restart kubelet so that it picks up the new value, by issuing the following command
talosctl -n <node ip> service kubelet restart
Continue setting up Mayastor using the official documentation.
NFS is an old pack animal long past its prime. NFS is slow, has all kinds of bottlenecks involving contention, distributed locking, single points of service, and more. However, it is supported by a wide variety of systems. You don’t want to use it unless you have to, but unfortunately, that “have to” is too frequent.
The NFS client is part of the
kubelet image maintained by the Talos team.
This means that the version installed in your running
kubelet is the version of NFS supported by Talos.
You can reduce some of the contention problems by parceling Persistent Volumes from separate underlying directories.
Ceph comes with an S3-compatible object store, but there are other options, as well. These can often be built on top of other storage backends. For instance, you may have your block storage running with Mayastor but assign a Pod a large Persistent Volume to serve your object store.
One of the most popular open source add-on object stores is MinIO.
The most common remaining systems involve iSCSI in one form or another. These include the original OpenEBS, Rancher’s Longhorn, and many proprietary systems. iSCSI in Linux is facilitated by open-iscsi. This system was designed long before containers caught on, and it is not well suited to the task, especially when coupled with a read-only host operating system.
iSCSI support in Talos is now supported via the iscsi-tools system extension installed. The extension enables compatibility with OpenEBS Jiva - refer to the local storage installation guide for more information.