xfs
[Top] [All Lists]

How to format RAID1 correctly

To: xfs@xxxxxxxxxxx
Subject: How to format RAID1 correctly
From: Helmut Tessarek <tessarek@xxxxxxxxxxx>
Date: Tue, 23 Sep 2014 20:46:34 -0400
Delivered-to: xfs@xxxxxxxxxxx
Openpgp: id=C11F128D
User-agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.9; rv:31.0) Gecko/20100101 Thunderbird/31.1.1
The information provided in the FAQ and on several web sites is not really
useful regarding RAID1.

According to the FAQ (entry 35):
The correct options to format a RAID1 (2 disks) with 64k chunk size is:
mkfs.xfs -d su=64k -d sw=1 /dev/mapper/data
But it also states that it would be automatically detected and used correctly,
yet
mkfs.xfs /dev/mapper/data
yields a different result:

[root@atvie01s ~]# mkfs.xfs -f /dev/mapper/data

meta-data=/dev/mapper/data       isize=256    agcount=4,
agsize=244173876 blks
         =                       sectsz=4096  attr=2, projid32bit=1
         =                       crc=0        finobt=0
data     =                       bsize=4096   blocks=976695504, imaxpct=5
         =                       sunit=0      swidth=0 blks
naming   =version 2              bsize=4096   ascii-ci=0 ftype=0
log      =internal log           bsize=4096   blocks=476902, version=2
         =                       sectsz=4096  sunit=1 blks, lazy-count=1
realtime =none                   extsz=4096   blocks=0, rtextents=0

Formel 1:

[root@atvie01s ~]# mkfs.xfs -f -d su=64k -d sw=1 /dev/mapper/data

meta-data=/dev/mapper/data       isize=256    agcount=32,
agsize=30521728 blks
         =                       sectsz=4096  attr=2, projid32bit=1
         =                       crc=0        finobt=0
data     =                       bsize=4096   blocks=976695296, imaxpct=5
         =                       sunit=16     swidth=16 blks
naming   =version 2              bsize=4096   ascii-ci=0 ftype=0
log      =internal log           bsize=4096   blocks=476902, version=2
         =                       sectsz=4096  sunit=1 blks, lazy-count=1
realtime =none                   extsz=4096   blocks=0, rtextents=0


Another inconsistency is that RAID1 doesn't use striping, so the chunk size
should be irrelevant in the first place.

So what is ultimately the correct way to format a RAID1?

Cheers,
  K. C.

-- 
regards Helmut K. C. Tessarek
lookup http://sks.pkqs.net for KeyID 0xC11F128D

/*
   Thou shalt not follow the NULL pointer for chaos and madness
   await thee at its end.
*/

<Prev in Thread] Current Thread [Next in Thread>