Re: [gentoo-user] 1-Terabyte drives - 4K sector sizes? -> bar performance so far

[Mark Knecht <markknecht@gmail.com>]

2010/2/14 Willie Wong <wwong@math.princeton.edu>:
> On Mon, Feb 15, 2010 at 01:48:01AM +0100, Frank Steinmetzger wrote:
<SNIP>
>>
>> action         SS (1st)   SS (2nd)   SS+2       SS+4       SS+6       SS+8
>> -------------+----------+----------+----------+----------+----------+----------
>> untar portage  3m12.517   2m55.916   1m46.663   1m35.341   1m47.829   1m43.677
>> rm portage     4m11.109   3m54.950   3m18.820   3m11.378   3m21.804   3m12.433
>> cp 1GB file    0m21.383   0m13.558   0m14.920   0m12.813   0m13.407   0m13.681




>
> Instead of guessing using this rather imprecise metric, why not just
> look up the serial number of your drive and see what the physical
> sector size is? If you don't want to open your box, you can usually
> get the information from dmesg.


hdparm capital eye works very nicely:

gandalf ~ # hdparm -I /dev/sda

/dev/sda:

ATA device, with non-removable media
        Model Number:       WDC WD10EARS-00Y5B1
        Serial Number:      WD-WCAV55464493
        Firmware Revision:  80.00A80
        Transport:          Serial, SATA 1.0a, SATA II Extensions,
SATA Rev 2.5, SATA Rev 2.6
Standards:
        Supported: 8 7 6 5
        Likely used: 8
<SNIP>

>
> Only caveat: don't trust the harddrive to report accurate geometry.
> This whole issue is due to the harddrives lying about their physical
> geometry to be compatible with older versions of Windows. So the
> physical sector size listed in dmesg may not be the real one. Which is
> why you are advised to look up the model number on the vendor's
> website yourself to determine the physical sector size.
>
> W
> --
> Willie W. Wong                                     wwong@math.princeton.edu

Very true...

Since this thread started and you help (me at least1) understand what
I was dealing with I got in contact with Mark Lord - the developer and
maintainer of the hdparm program. I was interested in seeing if we
could get hdparm to recognize this aspect of the drive. He was very
interested and asked me to send along additional info which he then
analyzed and decided that, at least at this time, even drives that we
__know__ are 4K sector sizes are not implementing any way of reading
it from the drive's firmware which is supported, at least in the newer
SATA specs. With that he decided that even for his own new 4K drives
he cannot do anything except either assume they are 4K and partition
appropriately or look up specs specifically as you suggest.

Currently I'm partial to the idea that all my sector starting
addresses will end in '000'. It's easy to remember and at most that
wastes (I think) 512K bytes between sectors so it's not much in terms
of the overall disk space. Just a couple of megabyte on a drive with 4
partitions.

= Mark