Questions about XFS

[harryxiyou]

On Fri, Oct 25, 2013 at 10:57 PM, Eric Sandeen <sandeen at 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)