VINUM should be operational w/ DEVFS now

[Matthew Dillon]

    The vinum softraid driver should now be operational with devfs
    in the master repo.  vinum should now be able to handle full 64 bit
    geometries (multi-terrabyte disk subsystems).

    In addition, vinum configurations may reference devices by serial
    number or devtab label.  for example:

        drive drive0 device raid0.s1d
        drive drive1 device raid1.s1d
        drive drive2 device raid2.s1d
        drive drive3 device raid3.s1d
        volume myvol
            plex org raid5 128k
                sd drive drive0 length 50g
                sd drive drive1 length 50g
                sd drive drive2 length 50g
                sd drive drive3 length 50g

    And in /etc/devtab:

        raid0           serno   WD-WCAVY0248702
        raid1           serno   WD-WCAVY0250739
        raid2           serno   WD-WCAVY0245831
        raid3           serno   WD-WCAVY0246122

    The vinum configuration stored on-media stores translated values,
    so on-media the devices will be stored by serial number.  e.g.
    /dev/serno/WD-WCAVY0246122.

    vinum roots may or may not still be broken, only because we do not
    have a getsynthvnode() function which can find a drive by its serial
    number.

    Generally speaking, anyone using vinum will want to reference devices
    by serial number now to avoid renumbering problems.

    TASKS STILL TO DO (any takers?):

    * Add a feature to getsynthvnode() to locate a drive by its serial
      numbers.

    * Add general disk_create() support for vinum volumes.  vinum
      historically insisted on being the partition manager for filesystems,
      but that isn't always convenient.

    * RAID-5 issues.  vinum isn't smart about RAID-5.  Have you every
      tried to rebuild parity on a 10TB vinum drive?  We may need a
      SOC project to fix this... that is, sub-divide the space into
      smaller chunks and keep track of activity in the chunks so a rebuild
      does not have to rebuild the entire freaking topology.

                                                -Matt

[Alex Hornung]

Matt,

as far as I can tell, finding a device by its serial number via
getsynthvnode should work already. It calls disklocate, which in turn
calls devfs_find_device_by_name.
devfs_find_device_by_name first iterates the cdev_t list, and if
nothing is found by the given name, it iterates the alias list to
match the name. If an alias is found, then the cdev to which it points
is returned.
So as long as make_dev_alias has already been called, one can call
getsynthvnode directly and it will work for serial numbers, as long as
"serno/" is prepended, as this is the alias' name.

To sum it up, prepending "serno/" to your call to getsynthvnode, if
you look for a serial number, should do the job.

Cheers,

Alex Hornung


2009/8/15 Matthew Dillon <dillon@...>:

>    The vinum softraid driver should now be operational with devfs
>    in the master repo.  vinum should now be able to handle full 64 bit
>    geometries (multi-terrabyte disk subsystems).
>
>    In addition, vinum configurations may reference devices by serial
>    number or devtab label.  for example:
>
>        drive drive0 device raid0.s1d
>        drive drive1 device raid1.s1d
>        drive drive2 device raid2.s1d
>        drive drive3 device raid3.s1d
>        volume myvol
>            plex org raid5 128k
>                sd drive drive0 length 50g
>                sd drive drive1 length 50g
>                sd drive drive2 length 50g
>                sd drive drive3 length 50g
>
>    And in /etc/devtab:
>
>        raid0           serno   WD-WCAVY0248702
>        raid1           serno   WD-WCAVY0250739
>        raid2           serno   WD-WCAVY0245831
>        raid3           serno   WD-WCAVY0246122
>
>    The vinum configuration stored on-media stores translated values,
>    so on-media the devices will be stored by serial number.  e.g.
>    /dev/serno/WD-WCAVY0246122.
>
>    vinum roots may or may not still be broken, only because we do not
>    have a getsynthvnode() function which can find a drive by its serial
>    number.
>
>    Generally speaking, anyone using vinum will want to reference devices
>    by serial number now to avoid renumbering problems.
>
>    TASKS STILL TO DO (any takers?):
>
>    * Add a feature to getsynthvnode() to locate a drive by its serial
>      numbers.
>
>    * Add general disk_create() support for vinum volumes.  vinum
>      historically insisted on being the partition manager for filesystems,
>      but that isn't always convenient.
>
>    * RAID-5 issues.  vinum isn't smart about RAID-5.  Have you every
>      tried to rebuild parity on a 10TB vinum drive?  We may need a
>      SOC project to fix this... that is, sub-divide the space into
>      smaller chunks and keep track of activity in the chunks so a rebuild
>      does not have to rebuild the entire freaking topology.
>
>                                                -Matt
>
>

[Matthew Dillon]

:To sum it up, prepending "serno/" to your call to getsynthvnode, if
:you look for a serial number, should do the job.
:
:Cheers,
:
:Alex Hornung
   
    Ah, ok.  Well, then theoretically a vinum root is possible.  I haven't
    tried it though.

                                                -Matt