Disk layout: OpenBSD OT

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Disk layout: OpenBSD OT

Friedrich Locke
Hi folks,

just wonder in a typical hard drive nowadays (SATA/SAS), the sector 0
is in the inner or outter track ?
Which tracks are faster: the inner ones or the outter ?

Thanks in advance.

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Re: Disk layout: OpenBSD OT

Miod Vallat
> just wonder in a typical hard drive nowadays (SATA/SAS), the sector 0
> is in the inner or outter track ?
> Which tracks are faster: the inner ones or the outter ?

Only the manufacturer knows.

Disks have been reporting fake geometries since more than 20 years. The
electronic on the disk will do the necessary work to use the disk
physical characteristic (with a varying number of sector per track) as
cleverly as it can.

Nowadays, you can't even be sure a given `software' is even contiguous
on the disk.

Just trust the disk and don't try to outsmart it, for it knows more
about the actual hardware than you do.

Miod

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Re: Disk layout: OpenBSD OT

Matthias Appel
Am 02.03.2013 20:59, schrieb Miod Vallat:

>> just wonder in a typical hard drive nowadays (SATA/SAS), the sector 0
>> is in the inner or outter track ?
>> Which tracks are faster: the inner ones or the outter ?
> Only the manufacturer knows.
>
> Disks have been reporting fake geometries since more than 20 years. The
> electronic on the disk will do the necessary work to use the disk
> physical characteristic (with a varying number of sector per track) as
> cleverly as it can.
>
> Nowadays, you can't even be sure a given `software' is even contiguous
> on the disk.
>
So, how is defrag (or avoiding fragmentation) done, if you can't be
certain how the blocks are aligned?

AFAIK, the last blocks are on the outside of the platters so, given a
CAV, the speed is higher.
The different speeds are measurable....but I don't know if noticeable
(but I dont think so!)

How SSDs handle block alignment is anoter story (wear-leveling et.al.)


Regards,

Matthias

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Re: Disk layout: OpenBSD OT

Shoufu Luo
In reply to this post by Friedrich Locke
usually, the inner tracks are fast, as I know

-Shoufu

Live, Love, Laugh

On Mar 2, 2013, at 14:55, Friedrich Locke <[hidden email]> wrote:

> Hi folks,
>
> just wonder in a typical hard drive nowadays (SATA/SAS), the sector 0
> is in the inner or outter track ?
> Which tracks are faster: the inner ones or the outter ?
>
> Thanks in advance.

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Re: Disk layout: OpenBSD OT

Kenneth R Westerback
In reply to this post by Matthias Appel
On Sat, Mar 02, 2013 at 10:04:50PM +0100, Matthias Appel wrote:

> Am 02.03.2013 20:59, schrieb Miod Vallat:
> >>just wonder in a typical hard drive nowadays (SATA/SAS), the sector 0
> >>is in the inner or outter track ?
> >>Which tracks are faster: the inner ones or the outter ?
> >Only the manufacturer knows.
> >
> >Disks have been reporting fake geometries since more than 20 years. The
> >electronic on the disk will do the necessary work to use the disk
> >physical characteristic (with a varying number of sector per track) as
> >cleverly as it can.
> >
> >Nowadays, you can't even be sure a given `software' is even contiguous
> >on the disk.
> >
> So, how is defrag (or avoiding fragmentation) done, if you can't be
> certain how the blocks are aligned?

You can't. You can only de-frag the 'view' the hardware provides you. You
can't outsmart it, so just be happy.

.... Ken

>
> AFAIK, the last blocks are on the outside of the platters so, given
> a CAV, the speed is higher.
> The different speeds are measurable....but I don't know if
> noticeable (but I dont think so!)
>
> How SSDs handle block alignment is anoter story (wear-leveling et.al.)
>
>
> Regards,
>
> Matthias

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Re: Disk layout: OpenBSD OT

Alexander Hall
In reply to this post by Shoufu Luo
On 03/03/13 00:04, Shoufu Luo wrote:
> usually, the inner tracks are fast, as I know

Since the RPM is constant and they can fit more data can on the outer,
longer, tracks, I believe you are wrong.

Not that it matters, since we don't know which ones we're served.

/Alexander

>
> -Shoufu
>
> Live, Love, Laugh
>
> On Mar 2, 2013, at 14:55, Friedrich Locke <[hidden email]> wrote:
>
>> Hi folks,
>>
>> just wonder in a typical hard drive nowadays (SATA/SAS), the sector 0
>> is in the inner or outter track ?
>> Which tracks are faster: the inner ones or the outter ?
>>
>> Thanks in advance.

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Re: Disk layout: OpenBSD OT

Michał Markowski
In reply to this post by Friedrich Locke
2013/3/2 Friedrich Locke <[hidden email]>:
> just wonder in a typical hard drive nowadays (SATA/SAS), the sector 0
> is in the inner or outter track ?
> Which tracks are faster: the inner ones or the outter ?

First track is outer-most, hence faster linear transfer rates at
beginning of disk, e.g.
http://mralpha.s3.amazonaws.com/SAMSUNG-HD501LJ-690G-MrAlpha.png

But it's generalization in terms of modern firmware.

--
Michał Markowski