Martin Steigerwald posted on Fri, 23 Aug 2013 14:58:07 +0200 as excerpted: > Am Freitag, 23. August 2013, 12:29:42 schrieb Xavier Bassery: >> On Fri, 23 Aug 2013 11:38:56 +0200 >> >> David Kofler <dkofler92@xxxxxxxxxxxxxx> wrote: >> > Hi, >> > can someone tell me which mount options are included in "defaults" >> > mount option? Couldn't find this in BTRFS Wiki. I'm using Debian >> > Wheezy 7.1 and Linux kernel 3.10.6. >> > Thanks in advance. >> >> Hi, >> you've looked at the wrong place. >> From mount man page: >> >> FILESYSTEM INDEPENDENT MOUNT OPTIONS defaults : Use default options: >> rw, suid, dev, exec, auto, nouser, async > > That are just VFS options, no BTRFS specific ones. > > A good way is to look at output of "mount" and "cat /proc/mounts". It > can differ from situation as well, for example SSD or not. > > But some hints at BTRFS default options are also on (search for > "default"): > > https://btrfs.wiki.kernel.org/index.php/Mount_options FWIW, space_cache seems to be the default now, and for ssds (detected if sysfs has a device rotation value of zero), ssd. There's some others that are the normal default now, but aren't listed (flushoncommit is one), as running with those features disabled can increase performance but also dramatically increases chance of data loss, so it's not recommended. Compression options are the big ones you may want to add, but they aren't default as usage is too varied for them to be a sane default. And of course ssd if it applies and isn't detected, and possibly ssd_spread. I recommend autodefrag for general use, as well, but you'll want to have it enabled when you first start copying data to the filesystem, and some distros don't enable it by default and setup a system on btrfs, which means there's fragmentation to begin with, and performance will probably be bad for awhile (even on newly setup systems!) when the option is first enabled as a result. You can readup on defrag on the wiki for a defrag command that should fix the problem, but unfortunately the command isn't as straightforward as one might expect. (Also note that if compression is enabled, a compressed file over a certain size, 128 MiB IIRC, but I'm not sure if that's compressed or uncompressed size, will appear fragmented to filefrag no matter what. That's an artifact of the way btrfs handles compression.) Inode_cache LOOKS good, but beware; people have reported problems with it and unsafe shutdowns or the like. So it's probably best to avoid it unless you really need it for your workload and judge it to be worth the risk. That's why it's not the default, yet. -- Duncan - List replies preferred. No HTML msgs. "Every nonfree program has a lord, a master -- and if you use the program, he is your master." Richard Stallman -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
