On Mon, Nov 25, 2013 at 09:58:21PM -0600, Stan Hoeppner wrote:
> On 11/25/2013 8:52 PM, Dave Chinner wrote:
> ...
> > sunit/swidth is in filesystem blocks, not sectors. Hence
> > sunit is 1MB, swidth = 2MB. While it's not quite correct
> > (su=512k,sw=1m), it's not actually a problem...
>
> Well that's what I thought as well, and I was puzzled by the 8 blocks
> value for the log sunit. So I double checked before posting, and 'man
> mkfs.xfs' told me
>
> sunit=value
> This is used to specify the stripe unit for a RAID device
> or a logical volume. The value has to be specified in
> 512-byte block units.
>
> So apparently the units of 'sunit' are different depending on which XFS
> tool one is using.
No they don't. sunit as a mkfs input value is determined by 512 byte
units. The output is given in units of "blks" i.e. the log block
size:
$ mkfs.xfs -N -l sunit=64 /dev/vdb
....
log =internal log bsize=4096 blocks=12800, version=2
= sectsz=512 sunit=8 blks, lazy-count=1
Which is given by the "bsize=4096" variable and so are, in this
case, 4k in size. input = 64 * 512 bytes = 8 * 4096 bytes = output
Remember, you can specify su rather than sunit, and they are
specified in sectors, filesystem blocks or bytes, and the output is
still in units of log block size:
# mkfs.xfs -N -b size=4096 -l su=8b /dev/vdb
....
log =internal log bsize=4096 blocks=12800, version=2
= sectsz=512 sunit=8 blks, lazy-count=1
# mkfs.xfs -N -l su=32k /dev/vdb
....
log =internal log bsize=4096 blocks=12800, version=2
= sectsz=512 sunit=8 blks, lazy-count=1
IOws, the input units can vary, but the output units are always the
same.
> That's a bit confusing. And 'man xfs_info'
> (xfs_growfs) doesn't tell us that sunit is given in filesystem blocks.
> I'm using xfsprogs 3.1.4 so maybe these have been corrected since.
It might seem confusing at first, but it's actually quite
consistent...
> > Again, lsunit is in filesystem blocks, so it is 32k, not 4k. And
> > yes, the default lsunit when the sunit > 256k is 32k. So, nothing
> > wrong there, either.
>
> So where should I have looked to confirm sunit reported by xfs_info is
> in fs block (4KB) multiples, not the in the 512B multiples of mkfs.xfs?
Explained above.
Cheers,
Dave.
--
Dave Chinner
david@xxxxxxxxxxxxx
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