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38 lines
1.6 KiB
Plaintext
38 lines
1.6 KiB
Plaintext
// Module included in the following assemblies:
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//
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// storage/understanding-persistent-storage.adoc[leveloffset=+1]
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//* microshift_storage/understanding-ephemeral-storage-microshift.adoc
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:_content-type: CONCEPT
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[id=storage-ephemeral-storage-overview_{context}]
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= Overview
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In addition to persistent storage, pods and containers can require
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ephemeral or transient local storage for their operation. The lifetime
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of this ephemeral storage does not extend beyond the life of the
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individual pod, and this ephemeral storage cannot be shared across
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pods.
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Pods use ephemeral local storage for scratch space, caching, and logs. Issues related to
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the lack of local storage accounting and isolation include the following:
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* Pods do not know how much local storage is available to them.
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* Pods cannot request guaranteed local storage.
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* Local storage is a best effort resource.
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* Pods can be evicted due to other pods filling the local storage,
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after which new pods are not admitted until sufficient storage
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has been reclaimed.
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Unlike persistent volumes, ephemeral storage is unstructured and
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the space is shared between all pods running on a
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node, in addition to other uses by the system, the container runtime,
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and {product-title}. The ephemeral storage framework allows pods to
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specify their transient local storage needs. It also allows {product-title} to
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schedule pods where appropriate, and to protect the node against excessive
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use of local storage.
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While the ephemeral storage framework allows administrators and
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developers to better manage this local storage, it does not provide
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any promises related to I/O throughput and latency.
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