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Loss of 15gb after formatting LaCie D2 120GB drive Redhat 8

Posted on 2003-03-29
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Hi, I have installed a LaCie 120gb D2 drive under firewire on RedHat 8.

When the drive is fired up on startup, dmesg reports:

SCSI device sda: 234441648 512-byte hdwr sectors (120034 MB)
 sda: sda1

Perfect.

But, after formatting the drive using fdisk and mke2fs, when I mount the
drive, df reports:

Filesystem           1K-blocks      Used Available Use% Mounted on
/dev/sda             115380224        20 109519164   1% /data

If a 120gb drive has 128849018880 bytes (120 * 1073741824)
it seems to me that I've lost nearly 10gb on this drive after formatting
(115380224 blocks = 118149349376 bytes which is 110.04gb).

fdisk /dev/sda displays the following when printing the table:

Disk /dev/sda: 255 heads, 63 sectors, 14593 cylinders
Units = cylinders of 16065 * 512 bytes

   Device Boot    Start       End    Blocks   Id  System
/dev/sda1             1     14593 117218241   83  Linux

All this doesn't make sense to me... are my calculations wrong?

Also, when I share the mounted drive on samba, and connect
to it on my mac, the mac reports that the drive only have 104gb
remaining, which is even worse....

Is this just a case of invalid calculations/reporting or have I
really lost between 10 and 16 gb of space after mounting?

Thanks!
paul.

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Question by:pschulz
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6 Comments
 
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Accepted Solution

by:
Brendt Hess earned 1000 total points
ID: 8231530
All too frequently, the GB drive capacity is calculated by dividing the total number of bytes by 1,000,000,000, not 1,073,741,824.

If you run the math, this appears to be what LaCie has done:

234441648 (hw blocks) * 512 (bytes per block) = 120034123776 (total bytes), not the 128849018880 bytes that a 120Gb (where Gb = 1,073,741,824) would have.

So, this drive has 120 Giga (billion) bytes capacity, not 120 GigaBytes
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Expert Comment

by:bjorndahlen
ID: 8232359
bhess got it right of course, and
a 120gB (billion bytes) drive generally contains 109.1 GB.
So in fact, with 110.04GB reported, your drive is actually
a little bit larger that 120gB.
Cheers, Bjorn  
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Expert Comment

by:kiranghag
ID: 8232784
and how much have you setup for swap??? or nothing at all..
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by:ryanf
ID: 8236053
Also keep in mind, both ext2 and ext3 default to 5% for reserve space... So if the drive fills, the machine won't halt (system still has some space available)... On a 120GB drive, all in one partition, you are talking 6GB right there... If you must, or want, to keep it all in one partition, use the -m option on your mkfs.ext2 command to reduce this to like 1%...

I would recommend splitting it up into a few 10GB drives... Might help performace... all depending on what you are gonna do with it :)

-Ryan
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Expert Comment

by:somanywindowsquestion
ID: 8242976
Paul,

Hard drive manufacturers typically use the decimal system when calculating disk space.

10^3 = 1,000 or 1 kilobyte
10^6 = 1,000,000 or 1 megabyte
10^9 = 1,000,000,000 or 1 gigabyte

However, MS-DOS or Windows calculates disk space in binary units.

2^10 = 1,024 or 1 kilobyte
2^20 = 1,048,576 or 1 megabyte
2^30 = 1,073,741,824 or 1 gigabyte

So, in a 30 GB example, taking a hard drive reference as 30,000,000 bytes, and dividing it by 1,073,741,824 equates to roughly 27.9 GB as shown by the operating system.



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Author Comment

by:pschulz
ID: 8243640
Thanks Guys.... much appreciated... makes sense, but I still feel ripped off :)... ryanf - yep, i'm going to split it up into a few drives and reduce the 6% to 1% - thanks!
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