RAID - Where has it all gone.....

I have four 750gb drives configured as Raid0.

Each drive has been detected as 695gb free space and following
creatiln of my RAID0 array I have 2048GB

So....

>From the advertised capacity of 750gb i am down to 695gb - thats a
loss of 4 x 55gb - 220gb

And after raid creation I have lost 732GB....

Is this right....?

And lastly - Is it really worth it...?

I think not....

Advertised capacity is not the same as formated capacity
I wont bore you with the details, its all been posted too often - google
will show you.

<> wrote in message
news: ups.com...
>I have four 750gb drives configured as Raid0.
>
> Each drive has been detected as 695gb free space and following
> creatiln of my RAID0 array I have 2048GB
>
> So....
>
>>From the advertised capacity of 750gb i am down to 695gb - thats a
> loss of 4 x 55gb - 220gb
>
> And after raid creation I have lost 732GB....
>
> Is this right....?
>
> And lastly - Is it really worth it...?
>
> I think not....
>

On Sat, 18 Aug 2007 13:09:38 -0700, wrote:

> I have four 750gb drives configured as Raid0.
>
> Each drive has been detected as 695gb free space

Welcome to, oh, 1998...

wrote:
> I have four 750gb drives configured as Raid0.
>
> Each drive has been detected as 695gb free space and following
> creatiln of my RAID0 array I have 2048GB
>
> So....
>
>>From the advertised capacity of 750gb i am down to 695gb - thats a
> loss of 4 x 55gb - 220gb
>
> And after raid creation I have lost 732GB....
>
> Is this right....?
>
> And lastly - Is it really worth it...?
>
> I think not....
>

There is a 2**32 sector limit for a "basic" disk. Or so I've heard.
If a sector is 512 bytes, this works out to 2.2TB for a basic disk.
(While changing sector sizes sounds cool, I'm not really sure whether
you can do it, and what disk types like ATA or SCSI, support it now.)

Windows has the capability to manage multiple disks, as a "dynamic" disk.
What that would require, is making each drive or a set of drives, available
as a separate volume, and then doing "something" to the group of drives,
to make one dynamic disk from it. I've heard that you can "span" a group of
disks, but I don't know what RAID formats are supported in desktop
versions of Windows.

I tried to find a reference on the Knowledgebase to the 2.2TB limit,
but didn't find anything.

There are some offhand references to "2.2" here:

http://www.2cpu.com/forums/showthread.php?p=584040

So the 2048GB capacity, could be related to starting at 2.2TB and losing
some due to partitioning or whatever. You might not actually be getting
4*750=3TB and losing a terabyte due to formatting.

It would be a fun experiment, to connect only three of those disks in
RAID0 and see if the final size, is exactly the same. You'd have to delete
the array, shut down, remove a disk, fire up the RAID setup, make array,
and check the size again.

You'd think this topic would be more popular, and there would be more
tutorials on the web about it.

A 64 bit OS is another possible solution. But that has its own set of
issues, especially if the machine is going to be used as a desktop
and not as a server box.

Paul

wrote:
> I have four 750gb drives configured as Raid0.
>
> Each drive has been detected as 695gb free space and following
> creatiln of my RAID0 array I have 2048GB
>
> So....
>
>> From the advertised capacity of 750gb i am down to 695gb - thats a
>> loss of 4 x 55gb - 220gb
>
> And after raid creation I have lost 732GB....
>
> Is this right....?
>
> And lastly - Is it really worth it...?
>
> I think not....

Read this and you'll understand the difference between advertised space
and real space.

http://www.acronis.com/homecomputing...megabytes.html

RobV wrote:
> wrote:
>
>>I have four 750gb drives configured as Raid0.
>>
>>Each drive has been detected as 695gb free space and following
>>creatiln of my RAID0 array I have 2048GB
>>
>>So....
>>
>>
>>>From the advertised capacity of 750gb i am down to 695gb - thats a
>>>loss of 4 x 55gb - 220gb
>>
>>And after raid creation I have lost 732GB....
>>
>>Is this right....?
>>
>>And lastly - Is it really worth it...?
>>
>>I think not....
>
>
> Read this and you'll understand the difference between advertised space
> and real space.
>
> http://www.acronis.com/homecomputing...megabytes.html
>
>

That Acronis article is wrong in as many ways as it is right.

For starters, it blames some of the capacity "loss" on the difference
between unformatted and formatted space, and claims that "Hard disk
manufacturers quote the unformatted size of their products". Once upon
a time, this was true; but, HD vendors have universally quoted only the
formatted size for many, many, years (decades, IIRC).

That article also notes the "loss" due to treating KB as 1,000B (and so on)
instead of 1,024B when, in fact, the HD vendors conform to international
standards, while M$ mis-applies the de facto standard for RAM to HDs.
(I do applaud the M$ practice of clearly showing HD capacity in both GBs --
albeit their flavor of GBs -- and actual bytes, under the HD's properties.)

Not such a great article in my opinion.
--
Cheers, Bob

Bob Willard wrote:
> RobV wrote:
>> wrote:
>>
>>> I have four 750gb drives configured as Raid0.
>>>
>>> Each drive has been detected as 695gb free space and following
>>> creatiln of my RAID0 array I have 2048GB
>>>
>>> So....
>>>
>>>
>>>> From the advertised capacity of 750gb i am down to 695gb - thats a
>>>> loss of 4 x 55gb - 220gb
>>>
>>> And after raid creation I have lost 732GB....
>>>
>>> Is this right....?
>>>
>>> And lastly - Is it really worth it...?
>>>
>>> I think not....
>>
>>
>> Read this and you'll understand the difference between advertised
>> space and real space.
>>
>> http://www.acronis.com/homecomputing...megabytes.html
>>
>>
>
> That Acronis article is wrong in as many ways as it is right.
>
> For starters, it blames some of the capacity "loss" on the difference
> between unformatted and formatted space, and claims that "Hard disk
> manufacturers quote the unformatted size of their products". Once
> upon a time, this was true; but, HD vendors have universally quoted
> only
> the formatted size for many, many, years (decades, IIRC).
>
> That article also notes the "loss" due to treating KB as 1,000B (and
> so on) instead of 1,024B when, in fact, the HD vendors conform to
> international standards, while M$ mis-applies the de facto standard
> for RAM to HDs. (I do applaud the M$ practice of clearly showing HD
> capacity in both GBs -- albeit their flavor of GBs -- and actual
> bytes, under the HD's properties.)
> Not such a great article in my opinion.

Tha's what happens when you depend on Google. At least it got someone
out to explain the difference. ;-)

On Sat, 18 Aug 2007 13:09:38 -0700, <> wrote:
: I have four 750gb drives configured as Raid0.
:
: Each drive has been detected as 695gb free space and following
: creatiln of my RAID0 array I have 2048GB
:
: So....
:
: >From the advertised capacity of 750gb i am down to 695gb - thats a
: loss of 4 x 55gb - 220gb
:
: And after raid creation I have lost 732GB....
:
: Is this right....?
:
: And lastly - Is it really worth it...?
:
: I think not....
:

Agreed but not for that reason. In your configuration if you lose one
drive you lose all four.

The 750 GB rating is their Unformatted capacity. Their Formatted capacity is
about 695 GB each.

--
---------------------
DaveW
<> wrote in message
news: ups.com...
>I have four 750gb drives configured as Raid0.
>
> Each drive has been detected as 695gb free space and following
> creatiln of my RAID0 array I have 2048GB
>
> So....
>
>>From the advertised capacity of 750gb i am down to 695gb - thats a
> loss of 4 x 55gb - 220gb
>
> And after raid creation I have lost 732GB....
>
> Is this right....?
>
> And lastly - Is it really worth it...?
>
> I think not....
>

DaveW wrote:
> The 750 GB rating is their Unformatted capacity. Their Formatted capacity is
> about 695 GB each.
>

That's a bit off, Dave. To pick one, the WD7500AAKS -- the vendor's site
lists the formatted capacity as 1,465,149,168 used (i.e. usable) sectors,
which is 750,156,374,016 Bytes; plainly 750 GB, using the international
standard definition of the G prefix which all HD vendors use.

It is true that init'ing a formatted HD under Windows will use some of that
formatted capacity, but probably not as much as your estimate. The 74GB HD
on this PC, for example, drops ~16MB (15,724,544 Bytes) due to the combined
effects of partitioning and Windows-formatting; the 250GB HD on this PC
drops ~12MB (11,769,856 Bytes). Note that what Windows and DOS call
formatting is not low-level formatting; it is the creation of a filesystem
(NTFS or FATxx) on a partition of a formatted device.

Let me estimate that a 750GB HD would have 3x the loss, due to init'ing
under Windows, that my 250GB HD has; ~35MB (35,309,568 Bytes); with that
estimate, the 750GB WD7500AAKS HD would be shown by Windows (in the
bottom line of the Explorer Properties of that HD) as:
Capacity: 750,121,106,448 bytes 698 GB

{While the purist in me wishes that Windows displayed that bottom line as:
Capacity: 750,121,106,448 bytes 698 GiB
it is clear, from context, that M$ is merely "abbreviating" GiB as GB.}
--
Cheers, Bob