[openstack-dev] [nova] increasing the number of allowed volumes attached per instance > 26

Belmiro Moreira moreira.belmiro.email.lists at gmail.com
Mon Jun 18 15:30:09 UTC 2018


Hi,
this looks reasonable to me but I would prefer B.
In this case the operator can configure the hard limit.
I don't think we more granularity or expose it using the API.

Belmiro

On Fri, Jun 8, 2018 at 3:46 PM Dan Smith <dms at danplanet.com> wrote:

> > Some ideas that have been discussed so far include:
>
> FYI, these are already in my order of preference.
>
> > A) Selecting a new, higher maximum that still yields reasonable
> > performance on a single compute host (64 or 128, for example). Pros:
> > helps prevent the potential for poor performance on a compute host
> > from attaching too many volumes. Cons: doesn't let anyone opt-in to a
> > higher maximum if their environment can handle it.
>
> I prefer this because I think it can be done per virt driver, for
> whatever actually makes sense there. If powervm can handle 500 volumes
> in a meaningful way on one instance, then that's cool. I think libvirt's
> limit should likely be 64ish.
>
> > B) Creating a config option to let operators choose how many volumes
> > allowed to attach to a single instance. Pros: lets operators opt-in to
> > a maximum that works in their environment. Cons: it's not discoverable
> > for those calling the API.
>
> This is a fine compromise, IMHO, as it lets operators tune it per
> compute node based on the virt driver and the hardware. If one compute
> is using nothing but iSCSI over a single 10g link, then they may need to
> clamp that down to something more sane.
>
> Like the per virt driver restriction above, it's not discoverable via
> the API, but if it varies based on compute node and other factors in a
> single deployment, then making it discoverable isn't going to be very
> easy anyway.
>
> > C) Create a configurable API limit for maximum number of volumes to
> > attach to a single instance that is either a quota or similar to a
> > quota. Pros: lets operators opt-in to a maximum that works in their
> > environment. Cons: it's yet another quota?
>
> Do we have any other quota limits that are per-instance like this would
> be? If not, then this would likely be weird, but if so, then this would
> also be an option, IMHO. However, it's too much work for what is really
> not a hugely important problem, IMHO, and both of the above are
> lighter-weight ways to solve this and move on.
>
> --Dan
>
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