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author | mckusick <mckusick@FreeBSD.org> | 2000-07-08 02:31:21 +0000 |
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committer | mckusick <mckusick@FreeBSD.org> | 2000-07-08 02:31:21 +0000 |
commit | 0ab089c771d8e35e9a21fa75813bff5cdc98c39b (patch) | |
tree | 4069828f78b96c864e4b8b27fa25d4b3d07e6ef6 | |
parent | 27334af100519b6a9465d2dc1ba716ac6bd37ccb (diff) | |
download | FreeBSD-src-0ab089c771d8e35e9a21fa75813bff5cdc98c39b.zip FreeBSD-src-0ab089c771d8e35e9a21fa75813bff5cdc98c39b.tar.gz |
Update to reflect current status.
-rw-r--r-- | sys/ufs/ffs/README.softupdates | 46 |
1 files changed, 42 insertions, 4 deletions
diff --git a/sys/ufs/ffs/README.softupdates b/sys/ufs/ffs/README.softupdates index 4e98c7d..3b9c675 100644 --- a/sys/ufs/ffs/README.softupdates +++ b/sys/ufs/ffs/README.softupdates @@ -1,9 +1,11 @@ $FreeBSD$ -Add option SOFTUPDATES to your kernel configuration. You should also -read the copyrights in the sources and the README file. +Using Soft Updates -Once you're running a kernel with soft update support, you need to enable +To enable the soft updates feature in your kernel, add option +SOFTUPDATES to your kernel configuration. + +Once you are running a kernel with soft update support, you need to enable it for whichever filesystems you wish to run with the soft update policy. This is done with the -n option to tunefs(8) on the UNMOUNTED filesystems, e.g. from single-user mode you'd do something like: @@ -13,8 +15,44 @@ e.g. from single-user mode you'd do something like: To permanently enable soft updates on the /usr filesystem (or at least until a corresponding ``tunefs -n disable'' is done). + +Soft Updates Copyright Restrictions + +As of June 2000 the restrictive copyright has been removed and +replaced with a `Berkeley-style' copyright. The files implementing +soft updates now reside in the sys/ufs/ffs directory and are +compiled into the generic kernel by default. + + +Soft Updates Status + +The soft updates code has been running in production on many +systems for the past two years generally quite successfully. +The two current sets of shortcomings are: + +1) On filesystems that are chronically full, the two minute lag + from the time a file is deleted until its free space shows up + will result in premature filesystem full failures. This + failure mode is most evident in small filesystems such as + the root. For this reason, use of soft updates is not + recommended on the root filesystem. + +2) If your system routines runs parallel processes each of which + remove many files, the kernel memory rate limiting code may + not be able to slow removal operations to a level sustainable + by the disk subsystem. The result is that the kernel runs out + of memory and hangs. + +Both of these problems are being addressed, but have not yet +been resolved. There are no other known problems at this time. + + +How Soft Updates Work + For more general information on soft updates, please see: + http://www.mckusick.com/softdep/ http://www.ece.cmu.edu/~ganger/papers/CSE-TR-254-95/ -- -Julian Elischer <julian@freebsd.org> +Marshall Kirk McKusick <mckusick@mckusick.com> +July 2000 |