-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA256 On Sun, Sep 20, 2015 at 9:49 PM, Wang, Zhiqiang wrote: >> -----Original Message----- >> From: ceph-users [mailto:ceph-users-bounces@xxxxxxxxxxxxxx] On Behalf Of >> Robert LeBlanc >> Sent: Saturday, September 19, 2015 12:18 PM >> To: ceph-users@xxxxxxxxxxxxxx >> Subject: Clarification of Cache settings >> >> -----BEGIN PGP SIGNED MESSAGE----- >> Hash: SHA256 >> >> Based on some discussion on where promotions were limited to only 10% >> increased the performance of the cache tier (sorry I can't find that discussion at >> the moment to reference). > > Probably here: http://tracker.ceph.com/projects/ceph/wiki/Rados_cache_tier_promotion_queue_and_throttling Yep, that sounds like it. >> I've been reading through >> http://ceph.com/docs/master/rados/operations/cache-tiering/#configuring-a-c >> ache-tier >> trying to figure out how to configure this type of promotion and try different >> values. I've reviewed the concepts of Bloom filters and so here are my >> questions: >> >> 1. Is a hit set an individual bloom filter? Or does the bloom filter keep track of >> the objects in the cache tier? > > Yes, a hit set is a bloom filter if you set its type to bloom filter. And it keeps track of the object access in the cache tier. > >> 2. If each hit set is a Bloom filter... It seems limiting the rate of promotion could >> be configured by setting min_{read,write}_recency_for_promote > 1 (The >> object would need to be in more than 1 hit set, where each hit set is 3,600 >> seconds). But the documentation specifies "Currently there is minimal benefit >> for hit_set_count > 1 since the agent does not yet act intelligently on that >> information." My assumption would be to set >> min_read,write}_recency_for_promote = 4, set hit_set_count = 15 and >> hit_set_period to 300. This would require an object to be accessed at least in 4 >> different 5 minute intervals in the last hour to be promoted. Is this how these >> values are intended to be used? Does hit_set_count > 1 still not do anything? > > The sentence "Currently there is minimal benefit for hit_set_count > 1 since the agent does not yet act intelligently on that information." is not valid anymore and is now removed from the documentation. And the current meaning of min_{read,write}_recency_for_promote is different from your understanding. Currently setting it to 1 would make it most difficult to promote. Checking the latest documentation of the master branch. And we've had some discussions to change its semantic to what you think, but haven't implemented yet. Looks like it makes more sense. I just did a git pull and checkout the master branch. The file /doc/rados/operations/cache-tiering.rst is the same as the website. Has the changes been merged yet? Which version of Ceph is able to take advantage of the multiple hitsets? If I'm just git challanged, can you provide the text here for me? >> 3. I understand that there was some discussion about changing the tracking for >> promotion. Will the new method be available in Jewell? Is the current approach >> still being developed? > > I had an implementation of the promotion queue and throttling in https://github.com/ceph/ceph/pull/5486. I'm excited about improvements in the caching tier as experience is gained. - ---------------- Robert LeBlanc PGP Fingerprint 79A2 9CA4 6CC4 45DD A904 C70E E654 3BB2 FA62 B9F1 -----BEGIN PGP SIGNATURE----- Version: Mailvelope v1.1.0 Comment: https://www.mailvelope.com wsFcBAEBCAAQBQJV/4WKCRDmVDuy+mK58QAAhrgP/2ws1cmwuW0UAz1dr7sW 3iLaS43uB446ocvbjfFxLzijvftFok7at1Lkv2tKjvDDPiSOiT5m2zmGw9RE K1eAJfWPP6um42yz8+ALfF/CAtCIuLlXMYm10iCGkJ7R7mml6Lga+Kxef6Qx /GqVQkSuYwLTT5+Vl6CA0k+fVUibWdc0Kp9vvuH6DcmtDX9R1F5U0gpmHx4m fs8UALk42Y9RJS+3kgxSP3O7ux569qMZorkFeCgOVPc46lZUD7goi3O4EKkA EQRs/R+BKr9bLhEhOSg3pFAOsZLtqn8FTdGZgKDbZ6Fh73clq9y9MtFOFBUY n3K0IVlyqdmLliMVwJzT7Q0asa4K70MOrQeLGXw0antHSfJMpqLT5+rwXsmk p76Sy1+pEoqR4SURZ3811xtCluRln05tPdXzsZG3x8McbM+97vXDskL0qaoE 1bFzz4dixP4IoryxTxLrg0Hg2asBYeJdd/9gQzhCUs1H3wfNRFUzVafXx95g R7t2CSdMRUeMkD6XWMKDV8bQgeYURdoR+mJqpdWS3gSTLhfVrIH9+USifUVP a4LUyQ0cP8G74n/ZM4XrcR5YtGmMWtW+pGE06i6WH0fKj4L3ZGk7IXNH/sq+ LC07xCmgOnRYp8ZMJUmZJFS8kU7mC6ZkAaCXwaqwVfVdA/0NlzJw1Lsx4nyk dHyG =oRFb -----END PGP SIGNATURE----- _______________________________________________ ceph-users mailing list ceph-users@xxxxxxxxxxxxxx http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
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