Open Stack

Hello Stackers,

Recently, we've received interest about increasing the maximum number of 
allowed volumes to attach to a single instance > 26. The limit of 26 is 
because of a historical limitation in libvirt (if I remember correctly) 
and is no longer limited at the libvirt level in the present day. So, 
we're looking at providing a way to attach more than 26 volumes to a 
single instance and we want your feedback.

We'd like to hear from operators and users about their use cases for 
wanting to be able to attach a large number of volumes to a single 
instance. If you could share your use cases, it would help us greatly in 
moving forward with an approach for increasing the maximum.

Some ideas that have been discussed so far include:

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.

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.

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?

Please chime in with your use cases and/or thoughts on the different 
approaches.

Thanks for your help,
-melanie