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
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