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Is journal useless in Petasan 2.0 (bluestore)?

Hello,

I'm still thinking about the sentence: "with bluestore you don't need a journal drive"
So is it useless to use a journal for normal HDD SATA drives with bluestore?

If so, why can I choose it in Petasan 2.0?
Or is the journal for a OSD not the option "osd_journal" but block.wal and block.db?

 

Greetings.

Or is the journal for a OSD not the option "osd_journal" but block.wal and block.db?

Yes in PetaSAN terminology, external block.wal and block.db are referred to as journal. This is to keep the ui / user experience the same whether you use bluestore or file store, also wal is write ahead log which is same thing as journal.

The external ssd journal with hdd drives in bluestore does give performance benefit, not as much as the benefit in filestore. however in combination with a write back cache controller you will get good performance. ideally use all flash with bluestore.