I recently came across the bluestore_prefer_deferred_size family of config options, for controlling the upper size threshold on deferred writes. Given a number of users suggesting that write performance in filestore is better than write performance in bluestore - because filestore writing to an SSD journal has much better write latency than bluestore does, writing into the main storage - I was wondering if just bumping the deferred write threshold up to some arbitrarily large value and therefore allowing most writes to be deferred would close the performance gap in these cases?
This raises the secondary question of whether or not the WAL size is limited in such a way that this would not work or would require other config changes to support. I'm not sure if the WAL size is limited to a certain maximum or it will just grow as required like the DB does. Rich
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