Open Stack

On 06/07/2018 01:56 PM, melanie witt wrote:
> 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?

If Cinder tracks volume attachments as consumable resources, then this 
would be my preference.

Best,
-jay