Hi Adam, We test it fairly regularly on our development test nodes. Basically what this does is cache data in the bluestore buffer cache on write. By default we only cache things when they are first read. The advantage to enabling this is that you immediately have data in the cache once it's written if you expect to read it back soon. The downside is that you might end up filling the cache with a bunch of cold data and force other things out. It can also make the caches spend more time evicting data which can be slow when running Ceph on fast NVMe drives (This is less of an issue in octopus though as we redesigned the way that bluestore's caches work to avoid using a single thread for cache trimming). One way to see if it's working is to issue a write workload to a freshly started cluster. With bluestore_default_buffered_write enabled you should see bluestore's buffer cache filling quickly with data while when it's off the cache should only start filling up once you start reading data. Mark ----- Original Message -----
From: "Adam Koczarski" <Adam@Koczarski.com> To: "ceph-users" <ceph-users@ceph.com> Sent: Tuesday, January 14, 2020 12:23:41 PM Subject: [ceph-users] bluestore_default_buffered_write = true
Has anyone ever tried using this feature? I've added it to the [global] section of the ceph.conf on my POC cluster but I'm not sure how to tell if it's actually working. I did find a reference to this feature via Google and they had it in their [OSD] section?? I've tried that too..
TIA
Adam
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