On Mon, 27 Jun 2016, myoungwon oh wrote: > Hi, I have questions for bluestore (4K random write case). > > So far, we have used NVRAM(PCIe) as journal and SSD (SATA) as data > disk (filestore). > Therefore, we got performance gain from NVRAM journal. > However, current Bluestore design seems that data (4K aligned) is > written to data disk first, then metadata is written to WAL rocksdb. > This design can remove “double write” in objectstore, but in our case, > NVRAM can not be utilized fully. > > So, my questions are that > > 1. Can bluestore write WAL first as filestore? You can do it indirectly with bluestore_min_alloc_size=65536, which will send anything smaller than this value through the wal path. Please let us know what effect this has on our latency/performance! > 2. If not, using bcache or flashcache for NVRAM on top of SSDs is right > answer? This is also possible, but I expect we'd like to make this work out of the box if we can! sage
