[parted-devel] [PATCH 1/2] fdasd: geometry handling updated from upstream s390-tools

[Phil Susi]

On 9/22/2015 6:08 PM, Viktor Mihajlovski wrote:
> DASD is a s390-specific disk architecture. The technical term which
> would be more accurate here is ECKD (enhanced count key data). In a
> nutshell, the Linux block layer is not prepared to handle variable
> block sizes of ECKD DASDs.

So it is kind of like that object storage stuff the SCSI committee has
been toying with for years?  Where you give it a key and an arbitrary
data set to store associated with that key?  And instead of using the
disk like that, you have to have a translation layer to make it behave
more like a regular disk?

> ECKD DASDs have to be formatted using a device specific ioctl. The
> formatting will provide the more or less familiar block structure
> (all blocks having the same size, typically 4K).
> However, the first track of a DASD has to be in a specific format
> called VTOC (volume table of contents) containing disk metadata.
> Traditionally, there is an ioctl to interface with this data, which
> however only works for a natively attached DASD.
> This patch is removing the necessity for the ioctls if the transport
> isn't native.

So instead of simply writing the VTOC to the first track, some crazy
person decided to make an ioctl for it, and when it is attached via
virtio, you skip this useless ioctl and just write to the first track
like a sane person?  Why keep the ioctl for direct attached disks?  Why
not just get rid of it in both cases?