File system blocks alignment

[Pieter de Goeje]

On Monday 28 December 2009 17:41:26 Pieter de Goeje wrote:
> On Monday 28 December 2009 13:30:22 Alexander Motin wrote:
> > Miroslav Lachman wrote:
> > > Alexander Motin wrote:
> > >> Thomas Backman wrote:
> > >>> On Dec 25, 2009, at 11:58 AM, Alexander Motin wrote:
> > >> |>>  Recently WD released first series of ATA disks with increased
> > >>
> > >> physical
> > >>
> > >>>> sector size. It makes writes not matching with 4K blocks inefficient
> > >>>> there.
> > >>>
> > >>> They don't expose this to the OS, though (not by default, anyway),
> > >>> but chop it up into 8 512-byte sectors for compatibility reasons.
> > >>> Just thought I'd point that out - I'm not even sure if you can get
> > >>> them to *not* do the compatibility thing and expose 4k-sized sectors.
> > >>
> > >> Latest ATA-8 specification allows drive to report both logical (512B)
> > >> and physical (4KB) sector sizes. ada driver able to fetch and report
> > >> that info to GEOM. If these drives not reporting it yet (are you
> > >> really sure?), it is only question of their firmware.
> > >
> > > There is an article about 4k sectors
> > > http://www.anandtech.com/storage/showdoc.aspx?i=3691
> > >
> > > It is completely hidden to OS in first versions.
> >
> > Thanks for the link, but all I see there is "but at this point there’s
> > no such tool". IMHO it doesn't meet it is not reported.
> >
> > We just need somebody with that drive to run on it `camcontrol identify`
> > from the fresh system and report what he sees.
>
> I've just ordered one of these disks. I expect it to arrive in a couple of
> days. Will let you know what it says when I have it :)

Ok, as Miroslav wrote, it does not report 4k sectors:

# camcontrol identify ada0
pass0: <WDC WD10EARS-00Y5B1 80.00A80> ATA-8 SATA 2.x device
pass0: 300.000MB/s transfers (SATA 2.x, UDMA6, PIO size 8192bytes)

protocol              ATA/ATAPI-8 SATA 2.x
device model          WDC WD10EARS-00Y5B1
firmware revision     80.00A80
serial number         WD-WCAV55072095
WWN                   50014ee2ae6664fd
cylinders             16383
heads                 16
sectors/track         63
sector size           logical 512, physical 512, offset 0
LBA supported         268435455 sectors
LBA48 supported       1953525168 sectors
PIO supported         PIO4
DMA supported         WDMA2 UDMA6
overlap not supported

Feature                      Support  Enable    Value           Vendor
read ahead                     yes      yes
write cache                    yes      yes
flush cache                    yes      yes
Native Command Queuing (NCQ)   yes              31/0x1F
Tagged Command Queuing (TCQ)   no       no      31/0x1F
SMART                          yes      yes
microcode download             yes      yes
security                       yes      no
power management               yes      yes
advanced power management      no       no      0/0x00
automatic acoustic management  yes      no      254/0xFE        128/0x80
media status notification      no       no
power-up in Standby            yes      no
write-read-verify              no       no      0/0x0
unload                         no       no
free-fall                      no       no

According to the anandtech article, this is because Windows XP does not work 
with sectorsize != 512 bytes.

- Pieter