Re: how to set load balance on multi active mds?

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Okay, you didn't mention that in your initial question. There was an interesting talk [3] at the Cephalocon in Amsterdam about an approach to combine dynamic and static pinning. But I don't know what the current status is. Regarding tuning options for the existing balancer I would hope that Gregory or Patrick could chime in here.

[3] https://www.youtube.com/watch?v=pDURll6Y-Ug

Zitat von zxcs <zhuxiongcs@xxxxxxx>:

Thanks a lot, Eugen!

we are using dynamic subtree pinning, we have another cluster using manual pinning, but we have many directory , and we need pin each dir for each request. so in our new cluster, we want to try dynamic subtree pinning. we don’t want to human kick in every time. Because some A directory hot, and sometimes B directory hot.. each directory has many subdirectory and sub-subdirectory...

But we found the load not balance on all mds when we using dynamic subtree pinning. So we want to know if any config we can tune for the dynamic subtree pinning. Thanks again!

Thanks,
xz

2023年8月9日 17:40,Eugen Block <eblock@xxxxxx> 写道:

Hi,

you could benefit from directory pinning [1] or dynamic subtree pinning [2]. We had great results with manual pinning in an older Nautilus cluster, didn't have a chance to test the dynamic subtree pinning yet though. It's difficult to tell in advance which option would suit best your use-case, so you'll probably have to try.

Regards,
Eugen

[1] https://docs.ceph.com/en/reef/cephfs/multimds/#manually-pinning-directory-trees-to-a-particular-rank [2] https://docs.ceph.com/en/reef/cephfs/multimds/#dynamic-subtree-partitioning-with-balancer-on-specific-ranks

Zitat von zxcs <zhuxiongcs@xxxxxxx <mailto:zhuxiongcs@xxxxxxx>>:

Hi, experts,

we have a product env build with ceph version 16.2.11 pacific, and using CephFS. Also enable multi active mds(more than 10), but we usually see load unbalance on our client request with these mds. see below picture. the top 1 mds has 32.2k client request. and the last one only 331.

this always lead our cluster into very bad situation. say many MDS report slow requests…
	...
     7 MDSs report slow requests
     1 MDSs behind on trimming
	…


So our question is how to set those mdss load balance? Could any one please help to shed some light here?
Thanks a ton!


Thanks,
xz

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