[mdlug] Linux VMs - virtual disk best practices

[Aaron Kulkis]

Drew wrote:
> What I meant to say is having the first partition begin at the
> beginning of the second cylinder (the MBR being on the first cylinder)
> and for each partition to be an integral number of cylinders..Some
> partition managers have a check box for this; personally I use the
> Ranish partitoner which shows what cylinder, head, and sector each
> partition starts and ends at and allows editing this data.
>

They're not REAL heads... look at your disk drive sometime, or look
at whta it's reporting to your bios... neither your 1/2-inch high
desktop drive, nor your 1/8th-inch high laptop drive has 63+ heads
in it.  A laptop drive is pushing it at 4 heads, yet most will report
63 heads to the bios.  I've seen some drives report 255 heads.  Given
that the number of heads is OVER-reported, most "cylinder boundaries"
as reported by the BIOS are actually in the middle of the physical
cylinders as they exist on the disk, and in some real/logical head
reporting combinations (63 logical heads/2 physical heads), many
logical cylinders even cross physicial cylinder boundaries.
This is why, in practice, most RAID 1 striping schemes use stripes
that are significantly smaller than even logical cylinder stripe
size -- to minimize the frequency of hitting physical cylinder
ends.

Basically, on a modern drive the C/H/S numbers are logical ONLY,
and bear NO relationship to the physical construction and layout
of the drive.


>
> On 3/22/13, Mat Enders <mat.enders at gmail.com> wrote:
>> What is a boumdary?
>>
>>
>>
>> On Fri, Mar 22, 2013 at 5:05 PM, Drew <drew4096 at gmail.com> wrote:
>>
>>> What about aligning partitions on cylinder boumdaries?
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