Re: [MooseFS-Users] CHUNKS_SOFT_DEL_LIMIT and CHUNKS_HARD_DEL_LIMIT on moosefs ce

[Krzysztof K. <krz...@mo...>]

Dear Eduardo,

We have tested to confirm that both parameters (CHUNKS_SOFT_DEL_LIMIT and CHUNKS_HARD_DEL_LIMIT) work as expected in MooseFS 2.0, but by design it works quite different than it was in MooseFS 1.6. 

* in MooseFS 1.6.x defined limits define how many deletions per second might be performed by any chunkserver
* in MooseFS 2.0.x and above the limits define how many concurrent deletions might be running by chunkserver 

The tests that we have performed show that even with the parameters set to the lowest values (CHUNKS_SOFT_DEL_LIMIT=1, CHUNKS_HARD_DEL_LIMIT=2) we were able to see almost 17k deletions per minute on a three node MooseFS 2.0 instance. This translates to ~95 deletions per second per chunkserver in MooseFS 1.6.x. world - probably you don’t have so much deletions and that’s why you don’t see the difference when changing the profiles.

MooseFS 2.0.x changed the way it interprets the parameters and the way it handles deletions. At the moment it’s not event possible to limit deletions as in MooseFS 1.6.x. Generally speaking MooseFS 2.0 employs improved algorithms for chunks deletions and can handle much more deletions without significant impact on overall system performance.

Do you see any performance problems with deletions on your MooseFS 2.0.x system or you are just concerned that the behaviour changed after the upgrade?

Best Regards,
Krzysztof Kielak
Director of Operations and Customer Support
Mobile: +48 601 476 440