Re: Same size drive has less usable space

["Darrick J. Wong" <darrick.wong@oracle.com>]

On Thu, Dec 20, 2018 at 01:13:05PM -0200, Luciano ES wrote:
> I have a new drive for backups. 
> I copied everything over and now I have this problem:
> 
> Filesystem      Size  Used 	 Avail 	Use% 	Mounted on
> /dev/sda1   	931G  914G   18G  	99% 	/xx
> /dev/sdb1   	931G  920G   11G  	99% 	/xxbkp
> 
> So 914GB from the old drive expand and become 920GB. The new drive 
> is supposed to be the same size, but for some reason it can't 
> really hold it all. I will be forced to waste precious gigabytes.
> 
> I tried to format the new one exactly like the old one, but 
> it was not possible:
> 
> $ xfs_info /xx
> meta-data=/dev/sda1     isize=256    agcount=8, agsize=30506944 blks
>          =              sectsz=4096  attr=2, projid32bit=1
>          =              crc=0        finobt=0 spinodes=0 rmapbt=0
>          =              reflink=0
> data     =              bsize=4096   blocks=244055552, imaxpct=25
>          =              sunit=0      swidth=0 blks
> naming   =version 2     bsize=4096   ascii-ci=0 ftype=0
> log      =internal      bsize=4096   blocks=119167, version=2
>          =              sectsz=4096  sunit=1 blks, lazy-count=1
> realtime =none          extsz=4096   blocks=0, rtextents=0
> 
> 
> $ xfs_info /xxbkp
> meta-data=/dev/sdb1     isize=512    agcount=8, agsize=61013888 blks
>          =              sectsz=512   attr=2, projid32bit=1
>          =              crc=1        finobt=1 spinodes=1 rmapbt=0
>          =              reflink=0
> data     =              bsize=2048   blocks=488111104, imaxpct=25

Just FYI you'll get a lot better performance from the filesystem if the
blocksize is the same as cpu page size (4k I think) and if the
filesystem isn't totally full.

But yeah, either unmount /xx and use xfs_copy one disk to the other, or
format the backup drive with the same parameters (I'll leave that to the
other parts of this thread).

--D

>          =              sunit=0      swidth=0 blks
> naming   =version 2     bsize=4096   ascii-ci=0 ftype=1
> log      =internal      bsize=2048   blocks=238335, version=2
>          =              sectsz=512   sunit=0 blks, lazy-count=1
> realtime =none          extsz=4096   blocks=0, rtextents=0
> 
> 
> I guess at least part of the problem is CRC enabled in the second 
> one. So, is there anything I can do to make all the data fit in the 
> new drive?
> 
> TIA
> 
> -- 
> Luciano ES
> >>