Open Stack

On 06/13/2018 09:58 AM, Blair Bethwaite wrote:
> Hi all,
> 
> Wondering if anyone can share experience with architecting Nova KVM 
> boxes for large capacity high-performance storage? We have some 
> particular use-cases that want both high-IOPs and large capacity local 
> storage.
> 
> In the past we have used bcache with an SSD based RAID0 write-through 
> caching for a hardware (PERC) backed RAID volume. This seemed to work 
> ok, but we never really gave it a hard time. I guess if we followed a 
> similar pattern today we would use lvmcache (or are people still using 
> bcache with confidence?) with a few TB of NVMe and a NL-SAS array with 
> write cache.
> 
> Is the collective wisdom to use LVM based instances for these use-cases? 
> Putting a host filesystem with qcow2 based disk images on it can't help 
> performance-wise... Though we have not used LVM based instance storage 
> before, are there any significant gotchas? And furthermore, is it 
> possible to use set IO QoS limits on these?

I've found /dev/null to be the fastest ephemeral storage system, bar none.

Not sure if you can set QoS limits on it though.

Best,
-jay