Hi, I doubt that you will get a satisfying response for cache-tier related questions. It hasn't been maintained for quite some time and is considered deprecated for years. It will be removed in one of the upcoming releases, maybe Reef. Regards, Eugen Zitat von lingu2008 <lingu2008@gmail.com>:
Hi all,
On one server with a cache tier on Samsung PM983 SSDs for an EC base tier on HDDs, I find the cache tier stops flushing or evicting when the cache tier is near full. With quite some gdb-debugging, I find the problem may be with the throttling mechanism. When the write traffic is high, the cache tier quickly fills its maximum request count and throttles further requests. Then flush stops because copy-from requests are throttled by the cache tier OSD. Ironically, the 256 requests already accepted by the cache tier cannot proceed, either, because the cache tier is full and cannot flush/evict.
While we may advise cache tier should not go full, this deadlock situation is not entirely comprehensible to me because a full cache usually can flush/evict as long as the base tier has space.
I wonder whether there has been some specific reasons for this behavior. My test environment is with version 15.2.17 but the code in 17.2.2 appears to handle this part of logic in the same way.
Cheers,
lin
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