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Re: Advanced format disk

To: Martin Rusko <martin.rusko@xxxxxxxxx>
Subject: Re: Advanced format disk
From: Zhu Han <schumi.han@xxxxxxxxx>
Date: Mon, 7 Nov 2011 22:51:17 +0800
Cc: xfs@xxxxxxxxxxx
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On Mon, Nov 7, 2011 at 10:44 PM, Martin Rusko <martin.rusko@xxxxxxxxx> wrote:
On Mon, Nov 7, 2011 at 3:12 AM, Zhu Han <schumi.han@xxxxxxxxx> wrote:
> Hi,
> I got several advanced format disk, whose physical size is 4096 bytes, but
> its logical size is 512 bytes:
> $ sudo fdisk -l /dev/sdb
> Disk /dev/sdb: 750.2 GB, 750156374016 bytes
> 255 heads, 63 sectors/track, 91201 cylinders
> Units = cylinders of 16065 * 512 = 8225280 bytes
> Sector size (logical/physical): 512 bytes / 4096 bytes
> I/O size (minimum/optimal): 4096 bytes / 4096 bytes
> Disk identifier: 0x00000000
> Disk /dev/sdb doesn't contain a valid partition table
> Is there any special tuning knob I should notice before formating it? IMHO,
> set the sector size as 4096 bytes is enough. The default block size is 4096
> bytes.
> $ sudo xfs_info /dev/sdb
> meta-data="" isize=256    agcount=4, agsize=45785912 blks
>                   =                       sectsz=4096  attr=2
> data          =                       bsize=4096   blocks=183143646,
> imaxpct=25
>                   =                       sunit=0      swidth=0 blks
> naming      =                        version 2              bsize=4096
> ascii-ci=0
> log            =internal               bsize=4096   blocks=89425, version=2
>                  =                       sectsz=4096  sunit=1 blks,
> lazy-count=1
> realtime   =none                   extsz=4096   blocks=0, rtextents=0

One thing is to make sure, that your partitions are aligned to
physical sector size. Recent fdisk will do it properly. See options
'-c' (or 'c' in interactive mode) which sets DOS compatibility mode
and '-u' (or 'u' in interactive mode) which sets units which fdisk
uses. You want no DOS compatibility and units of sectors. Then first
partition starts on 2048 sector (so 1MiB is available for GRUB for
example) and it's gets things nicely aligned ... 2048 logical sectors
= 256 physical sectors.

If the whole disk is used for the file system (it is not a bootable disk so no partition is created), can I ignore these settings safely?

If you are creating more than one partition, use something like +34G
while specifying end of the partition (so the next one is aligned as


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