From 6b9430b395997955be718244d0061eceb1319a9e Mon Sep 17 00:00:00 2001 From: Peter Eisentraut Date: Tue, 23 Apr 2019 12:03:57 +0200 Subject: [PATCH] doc: Update section on NFS --- doc/src/sgml/runtime.sgml | 71 ++++++++++++++++++++++----------------- 1 file changed, 40 insertions(+), 31 deletions(-) diff --git a/doc/src/sgml/runtime.sgml b/doc/src/sgml/runtime.sgml index 388dc7e966..7c76f5b8aa 100644 --- a/doc/src/sgml/runtime.sgml +++ b/doc/src/sgml/runtime.sgml @@ -229,42 +229,51 @@ Use of Secondary File Systems - - Use of Network File Systems - - - Network File Systems - - NFSNetwork File Systems - Network Attached Storage (NAS)Network File Systems + + File Systems - Many installations create their database clusters on network file - systems. Sometimes this is done via NFS, or by using a - Network Attached Storage (NAS) device that uses - NFS internally. PostgreSQL does nothing - special for NFS file systems, meaning it assumes - NFS behaves exactly like locally-connected drives. - If the client or server NFS implementation does not - provide standard file system semantics, this can - cause reliability problems (see ). - Specifically, delayed (asynchronous) writes to the NFS - server can cause data corruption problems. If possible, mount the - NFS file system synchronously (without caching) to avoid - this hazard. Also, soft-mounting the NFS file system is - not recommended. + Generally, any file system with POSIX semantics can be used for + PostgreSQL. (On Windows, all standard Windows file systems are + supported. XXX?) Users prefer different file systems for a variety of + reasons, including vendor support, performance, and familiarity. + Experience suggests that, all other things being equal, one should not + expect major performance or behavior changes merely from switching file + systems or making minor file system configuration changes. - - Storage Area Networks (SAN) typically use communication - protocols other than NFS, and may or may not be subject - to hazards of this sort. It's advisable to consult the vendor's - documentation concerning data consistency guarantees. - PostgreSQL cannot be more reliable than - the file system it's using. - + + NFS + + + NFS + + + It is possible to use an NFS file system for storing the + PostgreSQL data directory. The only + requirement is that the file system is mounted using the + hard option. With the hard option, + processes can hang indefinitely if there are network + problems, so this setup will require a careful monitoring setup. (The + soft option will interrupt system calls in case of + network problems, but the PostgreSQL will not + repeat system calls interrupted in this way, so any such interruption + will result in an I/O error being reported.) + PostgreSQL does nothing special for + NFS file systems, meaning it assumes + NFS behaves exactly like locally-connected drives. + + + + In some cases, an external storage product can be accessed either via NFS + or a lower-level protocol such as iSCSI. In the latter case, the storage + appears as a block device and any available file system can be created on + it. That approach might relieve the DBA from having to deal with some of + the idiosyncrasies of NFS, but of course the complexity of managing + remote storage then happens at other levels. + + -- 2.21.0