[ceph-users] advice needed for sizing of wal+db device for hdd

[Adrian Sevcenco]

Hi! i'm trying to estimate the size requiremenent for a wal+db volume for 26 TB HDD while trying to minimize the administrative hassle for configuration (meaning that i would prefer a wal+db volume not separate db from wal) (RGW usage, 3 node cluster)

AFAIU for metadata (db) device, i need raid as losing metadata, means
losing the associated OSD .. did i get this right?

So, what would the the best practice to map db+wal to hdd OSD?
should i do a mdraid from the 2 nvme and that to split in 12 partitions?




(i get that the recommended is 4%)



Thanks a lot!!!
Adrian

so, for a jbod that can go up to 44 drives (not all drives present, at most up to 12) i have 2x 6.4TB NVME should i split the nvme ssd in 12 namespaces and make individual mdraid for each and that map to osds? For a 6.4 TB NVME (divided to 12) and 26 TB OSD, the db/wal would be ~533 GB, so around 2.05% .. how terrible is this number for RGW usage At what size the data is in danger if db is too small and when it become safe but only with performance degradation?

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