> -----Original Message----- > From: Anthony D'Atri <anthony.datri@xxxxxxxxx> > Sent: Monday, August 24, 2020 7:30 PM > To: Tony Liu <tonyliu0592@xxxxxxxxxxx> > Subject: Re: Re: Add OSD with primary on HDD, WAL and DB on > SSD > > Why such small HDDs? Kinda not worth the drive bays and power, instead > of the complexity of putting WAL+DB on a shared SSD, might you have been > able to just buy SSDs and not split? ymmv. 2TB is for testing, it will bump up to 10TB for production. > The limit is a function of the way the DB levels work, it’s not > intentional. > > WAL by default takes a fixed size, like 512 MB or something. > > 64 GB is a reasonable size, it accomodates the WAL and allows space for > DB compaction without overflowing. For each 10TB HDD, what's the recommended DB device size for both DB and WAL? The doc recommends 1% - 4%, meaning 100GB - 400GB for each 10TB HDD. But given the WAL data size and DB data size, I am not sure if that 100GB - 400GB will be used efficiently. > With this commit the situation should be improved, though you don’t > mention what release you’re running > > https://github.com/ceph/ceph/pull/29687 I am using ceph version 15.2.4 octopus (stable). Thanks! Tony > >>> I don't need to create > >>> WAL device, just primary on HDD and DB on SSD, and WAL will be using > >>> DB device cause it's faster. Is that correct? > >> > >> Yes. > >> > >> > >> But be aware that the DB sizes are limited to 3GB, 30GB and 300GB. > >> Anything less than those sizes will have a lot of untilised space, > >> e.g a 20GB device will only utilise 3GB. > > > > I have 1 480GB SSD and 7 2TB HDDs. 7 LVs are created on SSD, each is > > about 64GB, for 7 OSDs. > > > > Since it's shared by DB and WAL, DB will take 30GB and WAL will take > > the rest 34GB. Is that correct? > > > > Is that size of DB and WAL good for 2TB HDD (block store and object > > store cases)? > > > > Could you share a bit more about the intention of such limit? > > > > > > Thanks! > > Tony > > _______________________________________________ > > ceph-users mailing list -- ceph-users@xxxxxxx To unsubscribe send an > > email to ceph-users-leave@xxxxxxx _______________________________________________ ceph-users mailing list -- ceph-users@xxxxxxx To unsubscribe send an email to ceph-users-leave@xxxxxxx
 |