I’m experiencing very slow write speed on a zfs pool that would otherwise be perfect to put my influxdb data on. To be clear, I’m not pointing the finger at influx - it’s the write speed for the drives/filesystem that’s slow.
I can get great write speed if I turn off the zfs intent log (zil), which is an intermediary storage location for write data. Ordinarily, this is not a recommended setting, however as I looked into it it occurred to me that the zil and the wal are really the same process, whereby data is temporarily stored on disk in one format while the computer takes its time to store it properly later.
My question is: how safe is it to disable the zil for ONLY the wal directory. If I keep the zil for the data and meta directories, then I have the same data integrity as normal for my long term storage. But I don’t know enough about either the zil or the wal to imagine the worst case scenario for what could happen. I’m hoping someone out there who knows more could opine.
Does influx even use the wal copy ordinarily, or just the duplicate data in the cache? What would happen if the wal became corrupted? In this case, I don’t care if I lose a few minutes of data, but I do care if I lose all my data.