Many thanks, Janne Ignazio Il giorno mer 20 mag 2020 alle ore 12:32 Janne Johansson < icepic.dz@xxxxxxxxx> ha scritto: > Den ons 20 maj 2020 kl 12:14 skrev Ignazio Cassano < > ignaziocassano@xxxxxxxxx>: > >> Hello Janne, so do you think we must move from 10Gbs to 40 or 100GBs to >> to make the most of nvme ? >> > > I think there are several factors to weigh in, when you need to maximize > performance, from putting BIOS into performance mode, having as fast > network as possible (some say 40 is 4x10 so 25Gbit is still faster in > latency than 40GE, but don't quote me on that) and so on. Also, in my > experience, nvmes can eat lots more parallel writes than ssds, so a single > test might just be easy enough for both drives to accept, whereas if you > had 100s of writers at the same time, it might favor the nvmes who would > not slow down as fast as ssds would in such a case. > Perhaps the nvmes will be far better everytime the rocksdb does > level-compactions so that it doesn't give you better write numbers in > tests, but less stalls when/if the DB needs reorganizing. > > On the other hand, if writes always are huge and evil and long-lasting, > sooner or later you will be capped by how much data the backend disks can > take, regardless of the performance of nvme/ssd WAL/DBs. > > Doing both local and remote (which you did) benchmarks, looking at iostat > for both nvme and ssds while doing the test and perhaps most important of > all, knowing when an acceptable result is achieved. > If you have a target to reach and you reach it then perhaps moving on to > other parts of designing is best. > > >> So we create a vm on the pool with db.wal on ssd and a vm on the pool with >>>> db/wal on nvme. >>>> Fio performances are almost the same on both . >>>> What do you think about it ? >>>> I expect better performance on pool with db/wal on pci express nvme >>>> >>> >>> Perhaps most of the time is lost talking over the network, making the >>> small differences in how well ssd -vs- nvme perform not visible. >>> >> > -- > May the most significant bit of your life be positive. > _______________________________________________ ceph-users mailing list -- ceph-users@xxxxxxx To unsubscribe send an email to ceph-users-leave@xxxxxxx
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