Re: WD Passport 2T hard drive formating question.
> You seem to have overlooked Darac Marjal's response.
I have not. I've just took a pause to do some additional reading and to
experiment a little.
I've tried 'tune2fs -m 1.0 /dev/sdXY' (found in Arch docs for Ext4).
The result was quite interesting. Both Nautilus and "df" showed the used
space on the drive reduced up to 19 MB. Then I fired GParted and it still
insisted that 29 GB were in use instead.
I recreated the file system from scratch using this time mkfs.ext4 with
the default options. The result - both Nautilus and "df" showed used
space on drive only 60 MB. But GParted again insisted on 29 GB being in
use.
Finally I recreated the file system one more time again with GParted.
After these all 3 parties, Nautilus, "df", and GParted agreed on 29 GB
being used.
Quite a mystery... :-)
> 29GB is not the space reserved for the super user. It is made of blocks
> set aside for inodes storage and super blocks replication (see option -T
> in mkfs.ext4 man page).
> I have been using xfs on external USB HDD because I never succeeded in
> the right value between too many inodes and not enough.
I'll use the drive for rsync snapshots type backup and will keep at least
5 snapshots recreated weekly. It happened to me already a couple of times
that the space taken by snapshots changed almost exponentially do to the
differences in snapshots (this is actually how I get 2T HDD idea). It's
quite a difficult task to figure out the correct inodes number in this
situation.
I'll give a try to XFS. The file system after created takes about 950 MB,
which is way better then 29.42 GB. And there is no need to predict the
required number of inodes.
Unless I decide to create Ext4 with mkfs2.ext4 and to rely on those low
"used" numbers. But right now I'm not sure the numbers are really
reliable.
> And the space reserved for the super user is really a space that can
> only be written by root. It is not a space required to operate the disk.
> It is made of blocks reserved to prevent a user from filling up the disk
> and prevent anybody (including root) from logging in. As far as I
> understand, you don't need it on an external storage. You can set -m0
> when formatting the disk.
man pages for mkfs2.ext4 say that the space reserved for root as also
needed to avoid fragmentation. Unfortunately the documentation in this
regard is extremely scanty and unclear. So far I've not found any
recommendations on how little is enough in other for Ext4 being able to
keep the drive not fragmented.
Probably another +1 for XFS, which just come with its own utilities.
Thanks.
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