Date: Wed, 12 Aug 2009 07:28:14 +0200 From: Pawel Jakub Dawidek <pjd@FreeBSD.org> To: Naeem Afzal <nafzal@hotmail.com> Cc: freebsd-fs@freebsd.org Subject: Re: filesystem size after newfs Message-ID: <20090812052814.GD1600@garage.freebsd.pl> In-Reply-To: <COL111-W50B8F353BF8FD65761B242D1040@phx.gbl> References: <COL111-W23AF31CB4D2944209932C6D1070@phx.gbl> <20090811191837.GB66530@keira.kiwi-computer.com> <COL111-W50B8F353BF8FD65761B242D1040@phx.gbl>
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On Wed, Aug 12, 2009 at 12:16:09AM +0000, Naeem Afzal wrote:
>=20
> Thanks you so much that was good explanation.=20
> For some reason using UFS1 or UFS2 did not make any size difference after=
I changed the block size and fragment size to minimum (4K/512).=20
> One more thing, I tried to make the same partition as geli with HMAC/SHA2=
56 authentication and it eats up even more space. Without this authenticati=
on, usage is pretty close to without geli.
> #geli init -a HMAC/SHA256 -P -K da2-64bytes.key /dev/ad1d
> # newfs -O 1 -U -l -m 0 -n -o space -f 512 -b 4096 -i 1048576 /dev/ad1d.e=
li/dev/ad1d.eli: 0.2MB (511 sectors) block size 4096, fragment size 512 =
using 1 cylinder groups of 0.25MB, 63 blks, 32 inodes. with soft=
updatessuper-block backups (for fsck -b #) at: 32
> #df -H /testFilesystem 1K-blocks Used Avail Capacity Mounted on/=
dev/ad1d.eli 228k 512B 228k 0% /test
>=20
> ada1.eli should have been 0.5MB, but seems like it is reserving some area=
for geli? How much is needed for HMAC/SHA256? What is allocation scheme if=
we go for this SHA256 authentication?
> regardsnaeem
To ensure atomicity of operations, geli stores hashes in the same
sector as the data. Creating geli providers with block size of 512 bytes
is very inefficient. It will consume two sectors for each sector, which
looks like this:
1 512b of data -----> 480b for data + 32b for hash
2 32b for data + 32b for hash + 448b unused
The most optimal block size for geli provider is 4kB, it consumes one
extra sector for every 8 sectors:
1 512b of data -----> 480b for data + 32b for hash
2 512b of data 480b for data + 32b for hash
3 512b of data 480b for data + 32b for hash
4 512b of data 480b for data + 32b for hash
5 512b of data 480b for data + 32b for hash
6 512b of data 480b for data + 32b for hash
7 512b of data 480b for data + 32b for hash
8 512b of data 480b for data + 32b for hash
9 256b for data + 32b for hash + 224 unused
--=20
Pawel Jakub Dawidek http://www.wheel.pl
pjd@FreeBSD.org http://www.FreeBSD.org
FreeBSD committer Am I Evil? Yes, I Am!
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