Re: mkfs.xfs doesn't detect size of storage correctly

Matthias Schniedermeyer
2008-01-29T17:16:55Z

On 29.01.2008 10:32, Matthias Schniedermeyer wrote:
> Hi
>
>
> Yesterday i bought a 750GB HDD.
> I encrypt nearly everything with loop-aes, so i also did it with this
> HDD.
>
> I create a "fake" partition table and:
> losetup -e aes256 -p 0 -o 4096 /dev/loop6 /dev/sdb < key
>
> This creates a loop with everything except the first 4KB, i.e. it leaves
> out the MBR and another 3,5KB.
>
> /proc/partions shows the correct(tm) size informations for the HDD and
> the loop:
> - snip -
> 7 6 732574580 loop6
> 8 16 732574584 sdb
> 8 17 732572001 sdb1
> - snip -
>
> But when i mkfs.xfs the loop
> #> mkfs.xfs /dev/loop6
> meta-data=/dev/loop6 isize=256 agcount=3, agsize=45785911 blks
> = sectsz=512 attr=2
> data = bsize=4096 blocks=137357733, imaxpct=25
> = sunit=0 swidth=0 blks
> naming =version 2 bsize=4096
> log =internal log bsize=4096 blocks=32768, version=2
> = sectsz=512 sunit=0 blks, lazy-count=0
> realtime =none extsz=4096 blocks=0, rtextents=0

I just found a workaround. :-)
As can be seen above the agcount is 3.

For a reason that lays years in the past, when there were issues with
the agcount (actually agsize), that to the best of my knowledge are
fixed years ago (but still cause a weird feeling whenever i see that
word) i just tried '-d agcount=4'

#> mkfs.xfs -l size=1024b -d agcount=4 /dev/loop6 -f
meta-data=/dev/loop6 isize=256 agcount=4, agsize=45785912 blks
= sectsz=512 attr=2
data = bsize=4096 blocks=183143645, imaxpct=25
= sunit=0 swidth=0 blks
naming =version 2 bsize=4096
log =internal log bsize=4096 blocks=32768, version=2
= sectsz=512 sunit=0 blks, lazy-count=0
realtime =none extsz=4096 blocks=0, rtextents=0

As can be seen the "blocks"-number is much higher.

#> df -k /mnt
Filesystem 1K-blocks Used Available Use% Mounted on
/dev/loop6 732570484 4256 732566228 1% /mnt

matches(tm) with the loop-size.

So i'm "burned" by agcount/agsize AGAIN, seems my weird feeling about
those two words are still with reason. ;-)

Bis denn

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