Re: Question about cam 4K quirks

On Sun, 10 Apr 2016 06:59:04 -0600
Alan Somers <asomers_at_freebsd.org> wrote:

> On Sun, Apr 10, 2016 at 12:56 AM, Tomoaki AOKI <junchoon_at_dec.sakura.ne.jp>
> wrote:
> 
> > Hi. Maybe freebsd-hardware list would be the right place, but it's not
> > so active. :-(
> >
> > Is 4K quirks needed for every HDDs/SSDs having physical sector size
> > 4096?
> >
> > If so, I would be able to provide patch for Crucial M550 and MX200.
> > (Possibly covers other models [BX200 etc.] by abstraction.)
> >
> >   M550(1TB):  device model          Crucial CT1024M550SSD1
> >               firmware revision     MU01
> >   MX200(1TB): device model          Crucial CT1024MX200SSD1
> >               firmware revision     MU03
> >     -> Abstracted with "Crucial CT*SSD*" or "Crucial CT*", as the part
> >        "1024" should vary with its capacity and can be 3 to 4 digits
> >        for now. I tried the former and confirmed "quirks=0x1<4K>"
> >        appears, which doesn't appear without adding the entry.
> >
> >
> > If not, is it sufficient if `camcontrol identify <device>` states
> > "physical 4096" on "sector size" line for everything in kernel and
> > related components (i.e., zfs-related ones)?
> >
> >
> > Regards.
> 
> 
> You only need quirk entries if the device fails to identify its physical
> size correctly.  If "camcontrol identify" states "physical 4096", then
> you're probably ok, but it's not the best place to ask.  "camcontrol
> identify" asks the device directly, whereas "diskinfo -v" asks the kernel.
> If "diskinfo -v" says "4096 stripesize" then you're definitely ok.
> 
> -Alan

Thanks for clarification.

Tried "diskinfo -v" as you noted (of course running the kernel without
adding quirks entry) and confirmed it saying "4096 # stripesize".
So it's already OK with current ata_da.c and scsi_da.c (no quirks is
needed).

OTOH, trying with Samsung 850 evo (the last one I have for now,
having quirks entry in current source), "diskinfo -v" says "4096 
# stripesize" while "camcontrol identify" says "physical 512".
This should be why quirks entries are needed (and implemented) for it.

I think stripesize should be primarily for RAID configuration, but
after 4k physical sectored drives  (so called AFT drives) appears,
applied to even for single drive configuration, too. Right?

If so, as writing blocks smaller than stripesize (except for the last
block of a file) is nonsense for RAID configuration, all write access
to HDDs/SSDs are constrained to use stripesize for minimum block size,
right?


Regards.

-- 
Tomoaki AOKI    junchoon_at_dec.sakura.ne.jp