Re: SATA: Is "DPO and FUA" ever supported?

[Sergei Shtylyov <sshtylyov@ru.mvista.com>]

Hello.

Michael Tokarev wrote:

> On each and every machine out there, and on every dmesg
> output posted on numerous mailinglists, I see messages
> similar to this:

> scsi 0:0:0:0: Direct-Access     ATA      ST3250620NS      3.AE PQ: 0 ANSI: 5
> SCSI device sda: 488397168 512-byte hdwr sectors (250059 MB)
> SCSI device sda: write cache: enabled, read cache: enabled, doesn't support DPO or FUA

> for SATA disk drives.  And I wonder -- are those features
> supported at all by linux, and/or are there disk drives
> out there which supports it as well?

    Don't know, the bits have just quite recently been included into ATA spec, 
IIRC...

> For my Seagate ST3250620NS SATA drive (it's a "server" drive,
> whatever it means), I can see -- at least --

>            *    Mandatory FLUSH_CACHE
>            *    FLUSH_CACHE_EXT

> reported by hdparm -I.  I wonder what "FLUSH CACHE EXT" means,

    It reports LBA48 of a failing sector while FLUSH CACHE can only report LBA28.

> and whenever it can be used to support DPO and/or FUA...

    DPO and FUA bits are a part of SCSI CDB and so only affect the block range 
specified by the command in question while FLUSH CACHE [EXT] operates on the 
whole cache -- so, it's not equivalent.

> Thanks.
> 
> /mjt

MBR, Sergei