Date: Mon, 5 Apr 2021 17:31:10 -0400 From: Gunther Schadow <raj@gusw.net> To: freebsd-performance@freebsd.org Subject: PosgtgreSQL hot standby reading WAL from muli-attached volume? Message-ID: <a1612d52-7a29-4058-b3a9-255634b1fe95@gusw.net>
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Hi, I wonder can we set up a hot standby in such a way that we don't need any log streaming nor shipping, where instead every hot standby just mounts the same disk in read-only mode which the master uses to write his WAL files? Even without a clustered file system, e.g., a UFS on FreeBSD, one can have the master mount in read-write mode while all the hot standbys would mount the volume read-only. Given that WAL logs are written out at a certain rate, one can at regular intervals issue mount -u /pg_wal and it should refresh the metadata, I assume. I am re-reading about hot-standby, and it strikes me that this method is essentially the "log shipping" method only that there is no actual "shipping" involved, the new log files simply appear all of a sudden on the disk. I suppose there is a question how we know when a new WAL file is finished appearing? And as I read the log-shipping method may not be suitable for hot standby use? Is this something that has been written about already? regards, -Gunther
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