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Subject: Re: Another WTF moment
From: Ian Lepore <freebsd@damnhippie.dyndns.org>
To: "Ronald F. Guilmette" <rfg@tristatelogic.com>
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Date: Sun, 16 Dec 2012 13:53:53 -0700
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On Sun, 2012-12-16 at 12:01 -0800, Ronald F. Guilmette wrote:
> 
> I have two Seagate ST380011A drives, both in the same single system.
> 
> On that system, I boot to the FreeBSD 9.1-RC3 LiveCD.
> 
> The resulting dmesg messages indicate the following regarding the two drives:
> 
> ada0 at ata0 bus 0 scbus2 target 0 lun 0
> ada0: <ST380011A 3.54> ATA-6 device
> ada0: 100.000MB/s transfers (UDMA5, PIO 8192bytes)
> ada0: 76318MB (156299375 512 byte sectors: 16H 63S/T 16383C)
> ada0: Previously was known as ad0
> ada1 at ata0 bus 0 scbus2 target 1 lun 0
> ada1: <ST380011A 3.06> ATA-6 device
> ada1: 100.000MB/s transfers (UDMA5, PIO 8192bytes)
> ada1: 76319MB (156301488 512 byte sectors: 16H 63S/T 16383C)
> ada1: Previously was known as ad1
> 
> 
> So, um, WTF?  One ST380011A is 156299375 sectors big, and the other one
> is 156301488 big.
> 
> How exactly does this happen?

Assuming the 3.06 and 3.54 are firmware revision numbers, one might
speculate that ongoing testing showed higher sector failure rates than
intially expected, and thus newer firmware sets aside a few more sectors
as spares.

-- Ian