Re: ARC-1120 and MD very sloooow
From: Dave Chinner <david@fromorbit.com>
Date: 2013-11-26 06:14:59
Also in:
linux-xfs
On Mon, Nov 25, 2013 at 09:58:21PM -0600, Stan Hoeppner wrote:
On 11/25/2013 8:52 PM, Dave Chinner wrote: ...quoted
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...
quoted
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@fromorbit.com _______________________________________________ xfs mailing list xfs@oss.sgi.com http://oss.sgi.com/mailman/listinfo/xfs