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Date:      Sun, 05 Jun 2005 12:58:41 -0700
From:      John Pettitt <jpp@cloudview.com>
To:        "D. Goss" <lists@dylangoss.com>
Cc:        freebsd-questions@freebsd.org
Subject:   Re: 36.4GB drive formats out to 32.8GB?  what am I missing please
Message-ID:  <42A35971.9030101@cloudview.com>
In-Reply-To: <3A0E3262-4941-48F5-9532-5E45359690F1@dylangoss.com>
References:  <3A0E3262-4941-48F5-9532-5E45359690F1@dylangoss.com>

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D. Goss wrote:

> I am adding some drives to an IBM xSeries 345.  I recently picked up 
> (via eBay) an IBM packaged Seagate drive, all with the proper IBM 
> part numbers as:
>
> U320 15k
> 36.4GB formatted capacity
> (IBM part 06P5776 / 06P5778, with Seagate drive ST336753LC)
>
> Looking up both the IBM part numbers and the Seagate part numbers via 
> Google, I consistantly get that the drive's formatted capacity is 
> 36.4GB.
>
> When partitioned either in "safe" or "dd" mode (via sysinstall) and 
> set to use the entire disk as one slice, once the drive is mounted I 
> show:
>
> # df -m
> /dev/da1s1      33617    0 30928     0%    /misc
>
> # df -h
> /dev/da1s1      33G    4.0K     30G     0%    /misc
>
> I'm seeing approx. 30,600MB (32.8GB?) free -
>
>
I suspect three things are goping on

1) disk makers specify GB as 1,000,000,000 bytes but everybody else
specifies 1,073,741,824 bytes (1024*1024*1024) this will yeild 33.9 GB
from your 36.4 GB drive

2) formatting itself takes some space for superblocks etc

3) some psace is reserved (man newfs and tunefs for info)

John



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