Strange unallocated areas showing on HDDs

I have 2 SATA HDDs installed, each with 1 primary plus 1 logical partition. The
partitions were all originally set up using EaseUS Partition Master. I recently
replaced that with MiniTool Partition Wizard, which shows a 7.87MB unallocated space
between primary and logical partitions on each HDD. Windows 8.1 Disk Management
doesn't "see" the unallocated areas. What gives? Are they needed buffer zones
separating partitions or would it be OK to merge that unused space into an existing
partition? I don't really need extra partition space, especially such a small
amount, but it's like learning I have extra space in the house that I can't use
because I can't get to it. That bothers me.

Larc

Larc wrote:
I have 2 SATA HDDs installed, each with 1 primary plus 1 logical partition. The
partitions were all originally set up using EaseUS Partition Master. I recently
replaced that with MiniTool Partition Wizard, which shows a 7.87MB unallocated space
between primary and logical partitions on each HDD. Windows 8.1 Disk Management
doesn't "see" the unallocated areas. What gives? Are they needed buffer zones
separating partitions or would it be OK to merge that unused space into an existing
partition? I don't really need extra partition space, especially such a small
amount, but it's like learning I have extra space in the house that I can't use
because I can't get to it. That bothers me.

Larc

There are two alignment schemes for disks. The older means,
traces back to CHS, or Cylinder,Head,Sector addressing. At
one time, the addressing was rather physical. For example,
I worked on a disk technology with a fixed number of sectors
per track, the number of heads was two per platter (one on top,
one on the bottom), with one platter having no bottom surface
because it was used for servo information. So at one time,
the CHS parts had physical significance.

http://en.wikipedia.org/wiki/Cylinder-head-sector

"As larger hard disks have come into use, a cylinder has
become also a logical disk structure, standardised at
16065 sectors (16065=255×63)."

What that means is, disks for quite a while have used "fake"
geometry. To make the best usage of address bits, they "pretend"
the drive has 255 heads. When in fact, a top of the line drive
has 8 heads. What it means is, the drive is no longer using
CHS as a means of picking a particular sector.

As a result of this, disks prepared on earlier OSes, the
information all seemed to be divisible by 63 (sectors per
track). Nothing ever starts in the middle of a track. Things
are rounded to at least the nearest (fake) track dimension.

If you use fdisk setup program in Linux, it basically
asks you how many cylinders you want. A cylinder is
255*63*512 bytes or 8225280 bytes (~8MB). Using the old
scheme, the next partition along, is aligned to the next
cylinder (the C of CHS). Up to 8MB of space could be "wasted",
between one partition and the next.

*******

Starting with Vista, and for Vista/Win7/Win8, disks use
megabyte alignment. Flash memory devices use power_of_two
addressing. The number "63" is a particularly bad choice
for flash memory. To aid in aligning logical structures
to physical flash pages, they selected a new alignment
measured in whole megabytes. Both Linux and Windows
support this option. A number like 1048576, fits nicely
in the arrangement of Flash memory blocks.

The reason this can work, is actual addressing on the disk
has been done with LBA (logical block address) for some time.
Similar to the addressing used on SCSI disks when they came out.
LBA is a single linear number, which specifies a sector you want.
The drive does its own math, using a processor, to figure out
in a zone recording world, where the sector is actually located.
And then seeks to that location.

So the drive doesn't really need CHS, but can equally well
be addressed with an LBA. But PCs have legacy components
in them (like the legacy BIOS modes still present on
motherboard BIOS), so occasionally the CHS notation is
still exposed. We "keep it for compatibility".

Old tools do not like new alignments. My copy of Partition Magic 7
just hates 1 megabyte alignment, throws up a dialog and quits.
And new tools, like a number of Linux versions I've tried, the
interface on those was just horrible, for selecting fake CHS
alignment, versus megabyte alignment. You could never get the
tools to measure things in "exact byte counts", to figure out
what was going on. If you could get exact numbers, you could
check if the number was divisible by 63, whether the disk
came from an old computer, and so on.

As a result, with new tools being designed to the newer
alignment standard (1 megabyte alignment, LBA addressing
as the norm, well suited to physical Flash memory based
storage devices), they may not make the old alignment
look particularly "natural". So you see gaps, depending
on the tastes of the software writer. The software writer
wants to show you the 7.8MB gap, to "rub your nose in it".

*******

Now, there are other cases to worry about. For very large
disks (2.2TB), GPT partitioning is used. And for those,
they seem to declare "spaces" like your space, as if
they were partitions. Whereas on MBR partitioned drives
(the old kind, 2.2TB capacity), we don't make a fuss
about spaces, and they have no recognition at all.
Except if some software clown wants to make a point,
by displaying them in the interface like they were
important or something. Seeing one, is a hint the disk
was partitioned by an older OS, or an older tool. But
is no reason to panic particularly. It just means
you live in an age of evolving standards (which can
be particularly annoying if you don't happen to have
just the right tools to figure out what is going on).

Note that, you can have disks where by accident, some
partitions are cylinder aligned and others are megabyte
aligned. And for the older tools, like my Partition Magic,
they just hate that. Call it an error and so on. When it
happens, you need newer tools.

Paul

On Fri, 12 Sep 2014 15:01:39 -0400, Paul wrote:

| There are two alignment schemes for disks. The older means,
| traces back to CHS, or Cylinder,Head,Sector addressing. At
| one time, the addressing was rather physical. For example,
| I worked on a disk technology with a fixed number of sectors
| per track, the number of heads was two per platter (one on top,
| one on the bottom), with one platter having no bottom surface
| because it was used for servo information. So at one time,
| the CHS parts had physical significance.
|
| http://en.wikipedia.org/wiki/Cylinder-head-sector
|
| "As larger hard disks have come into use, a cylinder has
| become also a logical disk structure, standardised at
| 16065 sectors (16065=255×63)."
|
| What that means is, disks for quite a while have used "fake"
| geometry. To make the best usage of address bits, they "pretend"
| the drive has 255 heads. When in fact, a top of the line drive
| has 8 heads. What it means is, the drive is no longer using
| CHS as a means of picking a particular sector.
|
| As a result of this, disks prepared on earlier OSes, the
| information all seemed to be divisible by 63 (sectors per
| track). Nothing ever starts in the middle of a track. Things
| are rounded to at least the nearest (fake) track dimension.
|
| If you use fdisk setup program in Linux, it basically
| asks you how many cylinders you want. A cylinder is
| 255*63*512 bytes or 8225280 bytes (~8MB). Using the old
| scheme, the next partition along, is aligned to the next
| cylinder (the C of CHS). Up to 8MB of space could be "wasted",
| between one partition and the next.
|
| *******
|
| Starting with Vista, and for Vista/Win7/Win8, disks use
| megabyte alignment. Flash memory devices use power_of_two
| addressing. The number "63" is a particularly bad choice
| for flash memory. To aid in aligning logical structures
| to physical flash pages, they selected a new alignment
| measured in whole megabytes. Both Linux and Windows
| support this option. A number like 1048576, fits nicely
| in the arrangement of Flash memory blocks.
|
| The reason this can work, is actual addressing on the disk
| has been done with LBA (logical block address) for some time.
| Similar to the addressing used on SCSI disks when they came out.
| LBA is a single linear number, which specifies a sector you want.
| The drive does its own math, using a processor, to figure out
| in a zone recording world, where the sector is actually located.
| And then seeks to that location.
|
| So the drive doesn't really need CHS, but can equally well
| be addressed with an LBA. But PCs have legacy components
| in them (like the legacy BIOS modes still present on
| motherboard BIOS), so occasionally the CHS notation is
| still exposed. We "keep it for compatibility".
|
| Old tools do not like new alignments. My copy of Partition Magic 7
| just hates 1 megabyte alignment, throws up a dialog and quits.
| And new tools, like a number of Linux versions I've tried, the
| interface on those was just horrible, for selecting fake CHS
| alignment, versus megabyte alignment. You could never get the
| tools to measure things in "exact byte counts", to figure out
| what was going on. If you could get exact numbers, you could
| check if the number was divisible by 63, whether the disk
| came from an old computer, and so on.
|
| As a result, with new tools being designed to the newer
| alignment standard (1 megabyte alignment, LBA addressing
| as the norm, well suited to physical Flash memory based
| storage devices), they may not make the old alignment
| look particularly "natural". So you see gaps, depending
| on the tastes of the software writer. The software writer
| wants to show you the 7.8MB gap, to "rub your nose in it".
|
| *******
|
| Now, there are other cases to worry about. For very large
| disks (2.2TB), GPT partitioning is used. And for those,
| they seem to declare "spaces" like your space, as if
| they were partitions. Whereas on MBR partitioned drives
| (the old kind, 2.2TB capacity), we don't make a fuss
| about spaces, and they have no recognition at all.
| Except if some software clown wants to make a point,
| by displaying them in the interface like they were
| important or something. Seeing one, is a hint the disk
| was partitioned by an older OS, or an older tool. But
| is no reason to panic particularly. It just means
| you live in an age of evolving standards (which can
| be particularly annoying if you don't happen to have
| just the right tools to figure out what is going on).
|
| Note that, you can have disks where by accident, some
| partitions are cylinder aligned and others are megabyte
| aligned. And for the older tools, like my Partition Magic,
| they just hate that. Call it an error and so on. When it
| happens, you need newer tools.
|
| Paul

Thanks very much for the great explanation. That answers a lot of questions. The
partitions were originally set up when I was running XP, likely with Partition Magic
7 or 8. Something I discovered on another computer is that even though Win 8.1
doesn't see the unallocated space, it will if the size is changed any. Even if it's
lessened. But Disk Management won't cooperate in merging the unallocated space into
either partition it's between. MiniTool Partition Wizard will do it, however.

Partition Wizard will also create partitions in nice, round numbers. I have an 8GB
partition at the front of a 2nd HDD for the main pagefile. Specifying 8,192MB
(8x1024) always got me a 7.99GB partition. With Partition Wizard, that entry results
in 8GB.

I decided to try Partition Wizard after reading reviews of it. All good so far. My
older paid version of EaseUS Partition Master had some problems with 64-bit Win 8.1.
The current free version works OK, but has too many popups hawking EaseUS products.
MiniTool Partition Wizard seems to be the best of both worlds so far. It's free and
does everything Partition Master does plus a few things it doesn't. And no popups!

Thanks again for the help.

Larc