Can you use a memory backed EmptyDir volume?

Solution `2` described by msau@ would work in the short term, but we'd much
rather invest in our existing plans for exposing local SSDs as Persistent
Volumes and get that feature to alpha by v1.7 for example.
More details on the existing plans/design here
<https://github.com/kubernetes/community/pull/306>.

--Vish

On Fri, Mar 3, 2017 at 10:42 AM, Richard Musiol <[email protected]>
wrote:

I would need a *Post*Stop hook. But yes, maybe the best solution right now
would be to wrap the agent into some helper that on SIGTERM first forwards
the signal to the agent and then does the cleanup before exiting itself.

'David Aronchick' via Kubernetes user discussion and Q&A <kubernetes-users@
googlegroups.com> schrieb am Fr., 3. März 2017 um 19:36 Uhr:

Is a preStop hook enough as a temp solution?

e.g. /bin/sh rm -rf <mounted-host-dir-foo>

https://kubernetes.io/docs/user-guide/container-environment/#hook-details

On Fri, Mar 3, 2017 at 10:24 AM, Richard Musiol <[email protected]>
wrote:

Hi Michelle, Hi Tim,

there is one local SSD per node, so yes, it is shared between many pods.

Solution 1 is already a step forward, but I would really like to use a
local SSD. The use case is that I'm running Buildkite agents on that
cluster and I want to autoscale them. The limits of a normal disk were very
quickly reached with that kind of workload, switching to the local SSD
solved it.

Solution 2 sounds involved, but I'm willing to be a guinea pig for this
because the workload is not production critical.

-Richard

'Michelle Au' via Kubernetes user discussion and Q&A <kubernetes-users@
googlegroups.com> schrieb am Do., 2. März 2017 um 23:33 Uhr:

Hi Richard,

Are you sharing the local SSD between many pods, or just one pod per SSD?

If sharing is ok, then in the short term we could look into one of the
following approaches:
1. Ability to create a GKE cluster with kubelet installed on top of a
PD-SSD.  Then all EmptyDirs will use this PD.  It's not going to perform as
well as a local SSD though.
2. Use the alpha flex volumes interface with an lvm plugin, that can carve
out lvs out of a vg comprised of local SSDs. The vgs would have to be
precreated by some DaemonSet on each node before any normal pods start
running.  This approach would be meant as a short term solution for now and
require some extra management by the user/admin.  Flex itself is alpha and
going through lots of revision.

If dedicated disks are required, then we don't have any short-term
solutions besides hostpath.  The long term solution is to expose disks as
LocalDisk PVs, and for the temporary use cases, have an "inline" option
where the PV gets created and destroyed with the pod.

-Michelle



On Thu, Mar 2, 2017 at 9:33 AM, 'Tim Hockin' via Kubernetes user discussion
and Q&A <[email protected]> wrote:

There isn't a clean way to express what you want today.  There are some
ideas about being able to express local storage as volumes, but that work
is a long pipeline for what feels.like a simple request.

We already have an idea of "medium" in emptyDir.  What if we extended
that?  The question becomes how to express that multitudes of potential SSD
technologies, current and yet to be developed, without resorting to calling
them all the same?

You could imagine a way to config kubelet to build a map of local
mountpoints as named "Local" media, and then allow users to request those.
It's imperfect in a lot of ways, but it might be tractable.

@vishh @msau this comes up not FREQUENTLY but enough that maybe we want to
think of a short term goal here?

Just thinking out loud...

On Mar 2, 2017 9:21 AM, "Richard Musiol" <[email protected]> wrote:

Hi,

I would like to use GKE's local SSD feature to have fast temporary disk
space.

The problem when using it with a "hostPath" volume as described on
https://cloud.google.com/container-engine/docs/local-ssd is that the
temporary files do not get removed when the pod gets deleted. Over time the
local SSD would fill up.

The volume type "emptyDir" would do what I want, but I don't see how to put
it on the local SSD.

Any ideas?

Cheers,
Richard

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  • [kubernetes-u... Richard Musiol
    • Re: [kub... 'Tim Hockin' via Kubernetes user discussion and Q&A
      • Re: ... 'Michelle Au' via Kubernetes user discussion and Q&A
        • ... Richard Musiol
          • ... 'David Aronchick' via Kubernetes user discussion and Q&A
            • ... Richard Musiol
              • ... 'Vishnu Kannan' via Kubernetes user discussion and Q&A
            • ... Rodrigo Campos
          • ... aledbf
            • ... Richard Musiol
              • ... Rodrigo Campos
              • ... 'Vishnu Kannan' via Kubernetes user discussion and Q&A
                • ... Richard Musiol

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