On Mon, 14 Oct 2019 at 10:31, Xiaoxi Chen <superdebuger@xxxxxxxxx> wrote: > > Several considerations on deployment: > > 1. How a traditional OSD(filestore, or bluestore W/O local cache) behavior if the OSD is selected as a PG member of the local-cache-pool? > hopefully the osd can just work as-is like an OSD with CACHE-FULL. > Only the pools whose cache mode is local will be affected, all other pools share the same osds will just act like before. > 2. Compared to other *global* caching mode, local-cache-mode cannot scale cache tier/storage tier separately, which will be a big caveats in real production environment, especially for those case that the working set is consistent but the archival data amount is keeping increasing. > > Overall it seems like a alternative for b-cache/flashcache/i-cas , more test or analysis is needed to understand the benefit of this approach over the existing b-cache solution. > Yes, this is a problem. For now, tier local mode only support SSD:HDD = 1:1 mode. If you want to extend cache's size under tier local mode, you can: - disable tier local mode - flush all fast objects to HDD - replace SSD dev to a large one - enable local mode again or add more SSD:HDD pairs into the related crush domain. > Honggang(Joseph) Yang <eagle.rtlinux@xxxxxxxxx> 于2019年10月13日周日 下午8:47写道： >> >> After the sysbench prepare operation is completed, about 48883MB of db >> data is generated. >> I set the fast partition to 30GB, so in the sysbench run stage, >> eviction was taking place. >> >> Mark Nelson <mnelson@xxxxxxxxxx> 于2019年10月12日周六 上午12:15写道： >> > >> > Hi Honggang, >> > >> > >> > I personally I find this very exciting! I was hoping that we might >> > eventually try local caching in bluestore especially given trends for >> > larger NVMe devices and pmem. When you were running performance tests, >> > did you run any tests where the data set size was significantly larger >> > than the available "fast" local tier cache (ie so that eviction was >> > taking place)? In the past, that's been the area we've really needed to >> > focus on getting right. >> > >> > >> > Mark >> > >> > >> > On 10/11/19 11:04 AM, Honggang(Joseph) Yang wrote: >> > > Hi, >> > > >> > > We implemented a new cache tier mode - local mode. In this mode, an >> > > osd is configured to manage two data devices, one is fast device, one >> > > is slow device. Hot objects are promoted from slow device to fast >> > > device, and demoted from fast device to slow device when they become >> > > cold. >> > > >> > > The introduction of tier local mode in detail is >> > > https://tracker.ceph.com/issues/42286 >> > > >> > > tier local mode: https://github.com/yanghonggang/ceph/commits/wip-tier-new >> > > >> > > This work is based on ceph v12.2.5. I'm glad to port it to master >> > > branch if needed. >> > > >> > > Any advice and suggestions will be greatly appreciated. >> > > >> > > thx, >> > > >> > > Yang Honggang _______________________________________________ Dev mailing list -- dev@xxxxxxx To unsubscribe send an email to dev-leave@xxxxxxx
