[CentOS] xfs not getting it right?

Wed Sep 20 15:52:03 UTC 2017
hw <hw at gc-24.de>

Stephen John Smoogen wrote:
> On 20 September 2017 at 10:47, hw <hw at gc-24.de> wrote:
>>
>> Hi,
>>
>> xfs is supposed to detect the layout of a md-RAID devices when creating the
>> file system, but it doesn´t seem to do that:
>>
>>
>> # cat /proc/mdstat
>> Personalities : [raid1]
>> md10 : active raid1 sde[1] sdd[0]
>>       499976512 blocks super 1.2 [2/2] [UU]
>>       bitmap: 0/4 pages [0KB], 65536KB chunk
>>
>>
>> # mkfs.xfs /dev/md10p2
>> meta-data=/dev/md10p2            isize=512    agcount=4, agsize=30199892
>> blks
>>          =                       sectsz=512   attr=2, projid32bit=1
>>          =                       crc=1        finobt=0, sparse=0
>> data     =                       bsize=4096   blocks=120799568, imaxpct=25
>>          =                       sunit=0      swidth=0 blks
>> naming   =version 2              bsize=4096   ascii-ci=0 ftype=1
>> log      =internal log           bsize=4096   blocks=58984, version=2
>>          =                       sectsz=512   sunit=0 blks, lazy-count=1
>> realtime =none                   extsz=4096   blocks=0, rtextents=0
>>
>>
>> # mkfs.xfs -f -d su=64m,sw=2 /dev/md10p2
>> meta-data=/dev/md10p2            isize=512    agcount=16, agsize=7553024
>> blks
>>          =                       sectsz=512   attr=2, projid32bit=1
>>          =                       crc=1        finobt=0, sparse=0
>> data     =                       bsize=4096   blocks=120799568, imaxpct=25
>>          =                       sunit=16384  swidth=32768 blks
>> naming   =version 2              bsize=4096   ascii-ci=0 ftype=1
>> log      =internal log           bsize=4096   blocks=58984, version=2
>>          =                       sectsz=512   sunit=8 blks, lazy-count=1
>> realtime =none                   extsz=4096   blocks=0, rtextents=0
>>
>>
>> The 64MB chunk size was picked my mdadm automatically.  The device is made
>> from two disks, and xfs either doesn´t figure that out, or it decided to
>> ignore the layout of the underlying RAID.
>>
>> Am I doing something wrong here, or is xfs in Centos somehow different?
>> Do, or must, we always specify the apporpriate values for su and sw or
>> did xfs ignore them because what it picked is better?
>>
>
> I don't know enough to answer, but I do have a question.. what were
> you expecting xfs to do (and what filesystems do that?) Thanks

I was expecting that the correct stripe size and stripe width would be used.