From: Peter Åstrand (peter@cendio.se)
Date: 03/20/02-09:34:49 AM Z
Date: Wed, 20 Mar 2002 16:34:49 +0100 (CET) From: Peter Åstrand <peter@cendio.se> Subject: Mount point crossing & space_avail Message-ID: <Pine.LNX.4.44.0203201517450.7744-100000@sofie.lambo.student.liu.se> Suppose we have a server S with three local filesystems: /dev/disk1 / /dev/disk2 /export/ (2 MiB bytes free) /dev/disk3 /export/pictures/ (2 GiB bytes free) The /export tree is exported via v4. The /export directory contains one directory called "documents" (in addition to "pictures", where disk3 is mounted). Client C mounts S:/export on /mnt. On the client, it looks like this: $ cd /mnt $ ls documents pictures $ User U at client C is planning to copy 500 MiB of data to /mnt/pictures and first checks if there is enough room for it: $ df Filesystem Size Used Avail Use% Mounted on ... S:/export ... ... 2M ... /mnt User U, which is totally unaware of the servers disk configuration, fsids and "All That Jazz :-)" screams and think it's time to buy more disks. U cannot now that "pictures" actually is on another filesystem. Or have I forgotten something? Wouldn't it be nice to have some way of querying the server of exported filesystems, e.g. add the functionality of the MOUNT protocols EXPORT procedure into v4? Some person asked if there was similiar functionality in v4 at Cthon, and if I remember it correctly the answer was "No, but most people will continue to run MOUNTD even with v4". I don't think that's a good solution. If v4 had some way of querying the server for exported fs's, an NFSv4-aware df program could be a bit more intelligent: $ df Filesystem Size Used Avail Use% Mounted on ... S:/export ... ... 2M ... /mnt S:/export/pictures ... ... 2G ... (not mounted) (Maybe it's a bad idea with a df program fetching information not only by calling statfs(2) but also by contacting server S over the network, but at least it would be possible.) But I suppose an EXPORTS operation in v4 will have to wait until 4.1, even if we agree on that it's a Good Thing? -- Peter Åstrand Telephone: +46-13-21 46 00 Cendio Systems E-mail: peter@cendio.se Teknikringen 3 583 30 Linköping Sweden
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