Re: Questions about XFS

harryxiyou
2013-10-25T16:24:13Z

On Fri, Oct 25, 2013 at 10:57 PM, Eric Sandeen <sandeen@sandeen.net> wrote:
> well, yes and no. It supports the "realtime subvolume" which is
> not really technically "realtime." It does have a more deterministic
> allocator, but it doesn't have GRIO (Guaranteed Realtime I/O) like
> IRIX does.

Hmmm..., however, I find the manual of mkfs.xfs tell me as follows.

-r realtime_section_options
These options specify the location, size, and other
parameters of the
real-time section of the filesystem. The valid
realtime_section_options
are:

rtdev=device
This is used to specify the device which
should contain the
real-time section of the filesystem. The
suboption value is
the name of a block device.

extsize=value
This is used to specify the size of the
blocks in the real-
time section of the filesystem. This value
must be a multiple
of the filesystem block size. The minimum
allowed size is the
filesystem block size or 4 KiB
(whichever is larger); the
default size is the stripe width for striped
volumes or 64
KiB for non-striped volumes; the maximum
allowed size is 1
GiB. The real-time extent size should be
carefully chosen to
match the parameters of the physical media used.

size=value
This is used to specify the size of the
real-time section.
This suboption is only needed if the
real-time section of the
filesystem should occupy less space than the
size of the par?
tition or logical volume containing the section.

After I run "mkfs.xfs -r rtdev=/dev/sda3 extsize=64K", I wonder what the
differences between '/dev/sda3' and '/dev/sda2' (/dev/sda2 is common XFS or
EXT2). The differences are as follows, right?

1, I/O speed of real-time '/dev/sda3' is faster?
2, The performance of '/dev/sda3’ is better?

Anything else?

--
Thanks
Weiwei Jia (Harry Wei)