Ceph OSD WAL disk

Aug 9, 2019
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I found out that the DB disk needs to plan 4% of the space from the OSD. But I didn't find any mention of the WAL disk. How much should I allocate for it? Maybe just put it on the DB and forget it? I would be grateful if someone could tell me.
 
Hi,
you don't really need an additional WAL disk, if you already have a DB disk. From the CEPH documentation:
If there is only a small amount of fast storage available (e.g., less than a gigabyte), we recommend using it as a WAL device. If there is more, provisioning a DB device makes more sense. The BlueStore journal will always be placed on the fastest device available, so using a DB device will provide the same benefit that the WAL device would while also allowing additional metadata to be stored there (if it will fit).