Re: mkfs.xfs cannot make sector size 64 KiB?

[Eric Sandeen]

Justin Piszcz wrote:
> Adding LKML to cc list.
>
> On Sun, 29 Apr 2007, Justin Piszcz wrote:
>
> > > From the manpage:
> >
> >       -b     Block size options.
> >
> >              This option specifies the fundamental block size of the 
> > filesys-
> >              tem.   The  valid suboptions are: log=value and 
> > size=value; only
> >              one can be supplied.  The block size is specified  
> > either  as a
> >              base two logarithm value with log=, or in bytes with 
> > size=. The
> >              default value is 4096 bytes (4 KiB), the minimum is 512, 
> > and the
> >              maximum is 65536 (64 KiB).  XFS on Linux currently only 
> > supports
> >              pagesize or smaller blocks.
> >
> > The maximum size is 64 KiB, yet it seems only up to 32 KiB is valid?

above is block size, not sector size

> > I am running x86_64.

then you are limited to blocks (and therefore sectors) <= page size, so 
<= 4096.

You can -mkfs- something bigger, but you won't be able to mount it.

> > $ uname -m
> > x86_64
> >
> >
> > p34:~# mkfs.xfs -b size=512 /dev/md3
> > mkfs.xfs: /dev/md3 appears to contain an existing filesystem (xfs).
> > mkfs.xfs: Use the -f option to force overwrite.
> > p34:~# mkfs.xfs -b size=4096 /dev/md3
> > mkfs.xfs: /dev/md3 appears to contain an existing filesystem (xfs).
> > mkfs.xfs: Use the -f option to force overwrite.
> > p34:~# mkfs.xfs -b size=8192 /dev/md3
> > mkfs.xfs: /dev/md3 appears to contain an existing filesystem (xfs).
> > mkfs.xfs: Use the -f option to force overwrite.
> > p34:~# mkfs.xfs -b size=16384 /dev/md3
> > mkfs.xfs: /dev/md3 appears to contain an existing filesystem (xfs).
> > mkfs.xfs: Use the -f option to force overwrite.
> > p34:~# mkfs.xfs -b size=32768 /dev/md3
> > mkfs.xfs: /dev/md3 appears to contain an existing filesystem (xfs).
> > mkfs.xfs: Use the -f option to force overwrite.
> > p34:~# mkfs.xfs -b size=65536 /dev/md3
> > illegal sector size 65536

This is mkfs.xfs trying to be smart about making larger "sectors" (== 
blocksize) on an md device, so that it does not switch the size of the 
IO requests between data & metadata, slowing things down significantly. 
 however,

       -s     Sector size options.

              This  option  specifies the fundamental sector size of 
the filesystem.  The
              valid suboptions are: log=value and size=value; only one 
can  be  supplied.
              The  sector  size  is  specified  either as a base two 
logarithm value with
              log=, or in bytes with size=.  The default value is 512 
bytes.  The minimum
              value  for  sector  size is 512; the maximum is 32768 (32 
KiB).  The sector
              size must be a power of 2 size and cannot be made larger 
than the  filesys-
              tem block size.


looks like a buglet where it is trying to make a block == sector == 64k, 
but sectors are limited to 32.

But this is not what you want anyway, assuming you want to actually 
*mount* your new  filesystem on x86_64.  Just make take default 
blocksize (4k) and be happy.

> > Usage: mkfs.xfs
> > /* blocksize */         [-b log=n|size=num]
> > /* data subvol */       [-d agcount=n,agsize=n,file,name=xxx,size=num,
> >                            (sunit=value,swidth=value|su=num,sw=num),
> >                            sectlog=n|sectsize=num,unwritten=0|1]
> > /* inode size */        [-i 
> > log=n|perblock=n|size=num,maxpct=n,attr=0|1|2]
> > /* log subvol */        [-l 
> > agnum=n,internal,size=num,logdev=xxx,version=n
> >                            sunit=value|su=num,sectlog=n|sectsize=num]
> > /* label */             [-L label (maximum 12 characters)]
> > /* naming */            [-n log=n|size=num,version=n]
> > /* prototype file */    [-p fname]
> > /* quiet */             [-q]
> > /* realtime subvol */   [-r extsize=num,size=num,rtdev=xxx]
> > /* sectorsize */        [-s log=n|size=num]
> > /* version */           [-V]
> >                        devicename
> > <devicename> is required unless -d name=xxx is given.
> > <num> is xxx (bytes), xxxs (sectors), xxxb (fs blocks), xxxk (xxx KiB),
> >      xxxm (xxx MiB), xxxg (xxx GiB), xxxt (xxx TiB) or xxxp (xxx PiB).
> > <value> is xxx (512 byte blocks).
> > p34:~#
> >
> > Unless, the page size is not <= 64 for x86_64?

it's not, but that's not why this broke.

-Eric

> > Justin.

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