Very Computer

The newfs command has a parameter (-m) that reserves a certain amount of disk
space (usually between 5-10%).  What is the reason for reserving this space?
Is it used to prevent too much disk fragmentation in some way?

        |The newfs command has a parameter (-m) that reserves a certain amount of dis
        |space (usually between 5-10%).  What is the reason for reserving this space?
        |Is it used to prevent too much disk fragmentation in some way?

Not really dealing with fragmentation. I believe the default in Solars
is around 10%. The purpose, I believe, is the threshold at which the
operating system reports the disk is full. So, for example, on a 100 MB
disk, set at 10%, the OS will report the disk is full when 90 MB is on
there. This is a safety feature, as it is a Bad Thing to get a disk
chock full.

--John

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Key fingerprint =  EF 3B F6 C5 B9 8A CC 8D  7F 05 3B 1F FE 90 7E 28

        |The newfs command has a parameter (-m) that reserves a certain amount of dis
        |space (usually between 5-10%).  What is the reason for reserving this space?
        |Is it used to prevent too much disk fragmentation in some way?

You don't mention what OS you're using, but here's from the Solaris man
page:

-m free         The minimum percentage of free space to maintain in the file
                                system. This space is off-limits to normal users. Once the
                                file system is filled to this threshold, only the super-user
                                can continue writing to the file system. The parameter can
                                be subsequently changed using the tunefs(1M) command. The
                                default is 10%.

READ: It is a Bad Thing to get your disks chock full.

--John

--

Key fingerprint =  EF 3B F6 C5 B9 8A CC 8D  7F 05 3B 1F FE 90 7E 28

Actually it is all to do with disk fragmentation!
The BSD FFS (Berkeley Fast File System (which is NOT fast)) reserves some
space (typically 10%). This is spread out over the disk so that if you
extend a file there is always some free space 'nearby'.

Making a disk 'chock full' is not always a bad thing - from a normal
user point of view the disk is 'chock full' when all of the unreserved
space is used.

Icarus
(Actually of course you can use up the 'nearby' space, in which case it
will switch to a different section of the disk with some free space. These
days 10% is far too much to reserve unless you have lots of big files, where
big means 1meg in this context, and no small ones. 5% is a sensible amount
to reserve these days when you have gigabyte disk drives)