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Old 07-03-2012, 07:56 AM
Ramon Hofer
 
Default Reason to use a partition

Hi all

I have accidentally found that it's possible to use a whole disk instead
of a partition spanning a whole disk.

I have two 2 TB disks. One (sdi) has a partition with jfs and the other
(sdk) has xfs directly on the disk:

/dev/sdi1 jfs 1.9T 1.9T 3.9G 100% /mnt/recordings
/dev/sdk xfs 1.9T 1.9T 3.3G 100% /mnt/recordings_temp

Is there a reason why one should use a partition spanning the whole disk
instead of creating the filesystem directly on the disk?


Best regards
Ramon


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Old 07-03-2012, 08:04 AM
Claudius Hubig
 
Default Reason to use a partition

Hello Ramon,

Ramon Hofer <ramonhofer@bluewin.ch> wrote:
> /dev/sdi1 jfs 1.9T 1.9T 3.9G 100% /mnt/recordings
> /dev/sdk xfs 1.9T 1.9T 3.3G 100% /mnt/recordings_temp
>
> Is there a reason why one should use a partition spanning the whole disk
> instead of creating the filesystem directly on the disk?

If you use a partition, it is possible to move the partition a little
bit (a few kilo-/megabytes is usually enough) to align it with the blocks
of the HDD.

I don’t know if this is possible when using disks directly. In any
case, it will be impossible to boot from such a disk, since there’s
no room for the MBR (or, if there is room for the MBR, the filesystem
will be unaligned with the disk blocks).

I therefore would always prefer to use a single-partition layout
rather than the raw disk.

Best regards,

Claudius
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Old 07-03-2012, 08:16 AM
Ramon Hofer
 
Default Reason to use a partition

On Tue, 03 Jul 2012 10:04:04 +0200, Claudius Hubig wrote:

> Hello Ramon,
>
> Ramon Hofer <ramonhofer@bluewin.ch> wrote:
>> /dev/sdi1 jfs 1.9T 1.9T 3.9G 100% /mnt/recordings /dev/sdk
>> xfs 1.9T 1.9T 3.3G 100% /mnt/recordings_temp
>>
>> Is there a reason why one should use a partition spanning the whole
>> disk instead of creating the filesystem directly on the disk?
>
> If you use a partition, it is possible to move the partition a little
> bit (a few kilo-/megabytes is usually enough) to align it with the
> blocks of the HDD.
>
> I don’t know if this is possible when using disks directly. In any case,
> it will be impossible to boot from such a disk, since there’s no room
> for the MBR (or, if there is room for the MBR, the filesystem will be
> unaligned with the disk blocks).
>
> I therefore would always prefer to use a single-partition layout rather
> than the raw disk.

Thanks for the answer!

I have created a new partition and the filesystem on it.


Cheers
Ramon


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Old 07-03-2012, 08:59 AM
Stan Hoeppner
 
Default Reason to use a partition

On 7/3/2012 3:16 AM, Ramon Hofer wrote:
> On Tue, 03 Jul 2012 10:04:04 +0200, Claudius Hubig wrote:
>
>> Hello Ramon,
>>
>> Ramon Hofer <ramonhofer@bluewin.ch> wrote:
>>> /dev/sdi1 jfs 1.9T 1.9T 3.9G 100% /mnt/recordings /dev/sdk
>>> xfs 1.9T 1.9T 3.3G 100% /mnt/recordings_temp
>>>
>>> Is there a reason why one should use a partition spanning the whole
>>> disk instead of creating the filesystem directly on the disk?
>>
>> If you use a partition, it is possible to move the partition a little
>> bit (a few kilo-/megabytes is usually enough) to align it with the
>> blocks of the HDD.
>>
>> I don’t know if this is possible when using disks directly. In any case,
>> it will be impossible to boot from such a disk, since there’s no room
>> for the MBR (or, if there is room for the MBR, the filesystem will be
>> unaligned with the disk blocks).
>>
>> I therefore would always prefer to use a single-partition layout rather
>> than the raw disk.
>
> Thanks for the answer!

Except Claudius gave you the wrong answer for your situation. You got
impatient again Ramon.

> I have created a new partition and the filesystem on it.

As I replied on XFS, there's ZERO reason for putting one partition on a
dedicated mythTV recording drive. And since this is an Advanced Format
drive, you instantly misaligned XFS by creating that partition. None of
the Squeeze partitioning tools understand ADF drives and will all
therefore create a sector misaligned partition, causing serious
performance degradation due to RMW cycles within the drive.

The definition of the word "partition" means to divide a whole into
smaller pieces. If you do not intend to divide your disk into smaller
pieces, but will be formatting the entire disk with a single filesystem,
then there is no reason to create a partition table with 1 partition.

Delete the partition, and directly format the drive with XFS, and you'll
be sector aligned, and everything will work as you expect.

--
Stan


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Old 07-03-2012, 09:29 AM
Ramon Hofer
 
Default Reason to use a partition

On Die, 2012-07-03 at 03:59 -0500, Stan Hoeppner wrote:
> On 7/3/2012 3:16 AM, Ramon Hofer wrote:
> > On Tue, 03 Jul 2012 10:04:04 +0200, Claudius Hubig wrote:
> >
> >> Hello Ramon,
> >>
> >> Ramon Hofer <ramonhofer@bluewin.ch> wrote:
> >>> /dev/sdi1 jfs 1.9T 1.9T 3.9G 100% /mnt/recordings /dev/sdk
> >>> xfs 1.9T 1.9T 3.3G 100% /mnt/recordings_temp
> >>>
> >>> Is there a reason why one should use a partition spanning the whole
> >>> disk instead of creating the filesystem directly on the disk?
> >>
> >> If you use a partition, it is possible to move the partition a little
> >> bit (a few kilo-/megabytes is usually enough) to align it with the
> >> blocks of the HDD.
> >>
> >> I don’t know if this is possible when using disks directly. In any case,
> >> it will be impossible to boot from such a disk, since there’s no room
> >> for the MBR (or, if there is room for the MBR, the filesystem will be
> >> unaligned with the disk blocks).
> >>
> >> I therefore would always prefer to use a single-partition layout rather
> >> than the raw disk.
> >
> > Thanks for the answer!
>
> Except Claudius gave you the wrong answer for your situation. You got
> impatient again Ramon.

I'm learning for exams and am happy for any distraction ;-)
And I wanted to ask at different places to be able to compare different
answers.


> > I have created a new partition and the filesystem on it.
>
> As I replied on XFS, there's ZERO reason for putting one partition on a
> dedicated mythTV recording drive. And since this is an Advanced Format
> drive, you instantly misaligned XFS by creating that partition. None of
> the Squeeze partitioning tools understand ADF drives and will all
> therefore create a sector misaligned partition, causing serious
> performance degradation due to RMW cycles within the drive.
>
> The definition of the word "partition" means to divide a whole into
> smaller pieces. If you do not intend to divide your disk into smaller
> pieces, but will be formatting the entire disk with a single filesystem,
> then there is no reason to create a partition table with 1 partition.

That's how I understand the word partition too.


> Delete the partition, and directly format the drive with XFS, and you'll
> be sector aligned, and everything will work as you expect.

Thanks!

I'm now copying the recordings :-)


Cheers
Ramon



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Old 07-03-2012, 09:33 AM
Claudius Hubig
 
Default Reason to use a partition

Hello Stan,

Stan Hoeppner <stan@hardwarefreak.com> wrote:
> As I replied on XFS, there's ZERO reason for putting one partition on a
> dedicated mythTV recording drive. And since this is an Advanced Format
> drive, you instantly misaligned XFS by creating that partition. None of
> the Squeeze partitioning tools understand ADF drives and will all
> therefore create a sector misaligned partition, causing serious
> performance degradation due to RMW cycles within the drive.

I can remember creating a correctly aligned partition about one year
ago on a 2 TB drive. I suspect this was with the tools from Squeeze
and I know that the logical block size of the drive differed from the
physical block size. However, I had to feed this information manually
to the partitioning program.

Best regards,

Claudius
--
Most people can't understand how others can blow their noses
differently than they do.
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http://chubig.net telnet nightfall.org 4242
 

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