[ANNOUNCE] multipath-tools-0.1.6

[ANNOUNCE] multipath-tools-0.1.6

[christophe varoqui]

Hello,

here goes multipath-tools-0.1.6

Changelog for this release :

* add the dmadm WIP tool (read MD superblocks and create
  corresponding devmaps when possible)
* plug fd leak in TUR path checker (multipathd)

Please note dmadm should not be run anywhere near a production machine with useful data on MD raids.
That said comments and contributions are welcome.

Downloads and docs at http://christophe.varoqui.free.fr

regards,
cvaroqui



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[ANNOUNCE] multipath-tools-0.1.6

[christophe varoqui]

Hello,

here goes multipath-tools-0.1.6

Changelog for this release :

* add the dmadm WIP tool (read MD superblocks and create
  corresponding devmaps when possible)
* plug fd leak in TUR path checker (multipathd)

Please note dmadm should not be run anywhere near a production machine with useful data on MD raids.
That said comments and contributions are welcome.

Downloads and docs at http://christophe.varoqui.free.fr

regards,
cvaroqui

Re: [dm-devel] [ANNOUNCE] multipath-tools-0.1.6

[thornber]

On Sun, Apr 25, 2004 at 11:54:59PM +0200, christophe varoqui wrote:
> * add the dmadm WIP tool (read MD superblocks and create
>   corresponding devmaps when possible)

:)

- Joe


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Re: [dm-devel] [ANNOUNCE] multipath-tools-0.1.6

[thornber]

On Sun, Apr 25, 2004 at 11:54:59PM +0200, christophe varoqui wrote:
> * add the dmadm WIP tool (read MD superblocks and create
>   corresponding devmaps when possible)

:)

- Joe

Re: [dm-devel] [ANNOUNCE] multipath-tools-0.1.6

[christophe.varoqui]

Selon thornber@redhat.com:

> On Sun, Apr 25, 2004 at 11:54:59PM +0200, christophe varoqui wrote:
> > * add the dmadm WIP tool (read MD superblocks and create
> >   corresponding devmaps when possible)
> 
> :)
> 
Any insight on where to put the log of the mirror target when mapping over a
MD-created raid1 ?


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Re: [dm-devel] [ANNOUNCE] multipath-tools-0.1.6

[christophe.varoqui]

Selon thornber@redhat.com:

> On Sun, Apr 25, 2004 at 11:54:59PM +0200, christophe varoqui wrote:
> > * add the dmadm WIP tool (read MD superblocks and create
> >   corresponding devmaps when possible)
> 
> :)
> 
Any insight on where to put the log of the mirror target when mapping over a
MD-created raid1 ?

Re: [dm-devel] [ANNOUNCE] multipath-tools-0.1.6

[thornber]

On Tue, Apr 27, 2004 at 11:57:58AM +0200, christophe.varoqui@free.fr wrote:
> Selon thornber@redhat.com:
> 
> > On Sun, Apr 25, 2004 at 11:54:59PM +0200, christophe varoqui wrote:
> > > * add the dmadm WIP tool (read MD superblocks and create
> > >   corresponding devmaps when possible)
> > 
> > :)
> > 
> Any insight on where to put the log of the mirror target when mapping over a
> MD-created raid1 ?

MD effectively uses a log with a single region in it.  So we only need
3 sectors (2 for the header 1 for the bitset) for the log, is there
any space in the MD metadata where this could be placed ?

- Joe


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Re: [dm-devel] [ANNOUNCE] multipath-tools-0.1.6

[thornber]

On Tue, Apr 27, 2004 at 11:57:58AM +0200, christophe.varoqui@free.fr wrote:
> Selon thornber@redhat.com:
> 
> > On Sun, Apr 25, 2004 at 11:54:59PM +0200, christophe varoqui wrote:
> > > * add the dmadm WIP tool (read MD superblocks and create
> > >   corresponding devmaps when possible)
> > 
> > :)
> > 
> Any insight on where to put the log of the mirror target when mapping over a
> MD-created raid1 ?

MD effectively uses a log with a single region in it.  So we only need
3 sectors (2 for the header 1 for the bitset) for the log, is there
any space in the MD metadata where this could be placed ?

- Joe

Re: [dm-devel] [ANNOUNCE] multipath-tools-0.1.6

[christophe.varoqui]

Selon thornber@redhat.com:

> > Any insight on where to put the log of the mirror target when mapping over
> a
> > MD-created raid1 ?
> 
> MD effectively uses a log with a single region in it.  So we only need
> 3 sectors (2 for the header 1 for the bitset) for the log, is there
> any space in the MD metadata where this could be placed ?
> 
Nope : the sb is 4096 bytes long, and is full of holes. The biggest one is 128
bytes long, at the tail. We could lower the maximum number of device in a raid
from 27 to 21 to free 3 sectors, but it won't be appreciated and would leave us
with the most fundamental problem : logging in the MD superblock would corrupt
the checksum ... :(


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Re: [dm-devel] [ANNOUNCE] multipath-tools-0.1.6

[christophe.varoqui]

Selon thornber@redhat.com:

> > Any insight on where to put the log of the mirror target when mapping over
> a
> > MD-created raid1 ?
> 
> MD effectively uses a log with a single region in it.  So we only need
> 3 sectors (2 for the header 1 for the bitset) for the log, is there
> any space in the MD metadata where this could be placed ?
> 
Nope : the sb is 4096 bytes long, and is full of holes. The biggest one is 128
bytes long, at the tail. We could lower the maximum number of device in a raid
from 27 to 21 to free 3 sectors, but it won't be appreciated and would leave us
with the most fundamental problem : logging in the MD superblock would corrupt
the checksum ... :(

Re: [dm-devel] [ANNOUNCE] multipath-tools-0.1.6

[Mike Tran]

On Tue, 2004-04-27 at 05:09, thornber@redhat.com wrote:
> On Tue, Apr 27, 2004 at 11:57:58AM +0200, christophe.varoqui@free.fr wrote:
> > Selon thornber@redhat.com:
> > 
> > > On Sun, Apr 25, 2004 at 11:54:59PM +0200, christophe varoqui wrote:
> > > > * add the dmadm WIP tool (read MD superblocks and create
> > > >   corresponding devmaps when possible)
> > > 
> > > :)
> > > 
> > Any insight on where to put the log of the mirror target when mapping over a
> > MD-created raid1 ?
> 
> MD effectively uses a log with a single region in it.  So we only need
> 3 sectors (2 for the header 1 for the bitset) for the log, is there
> any space in the MD metadata where this could be placed ?
> 
> - Joe

The MD device size is 64K aligned and MD superblock size is 4K.  In term
of sectors, the calculation is as follows:

MD_SB_BYTES 4096
MD_SB_SECTORS (MD_SB_BYTES / 512)

// x is the child device size in sectors.

#define MD_RESERVED_BYTES (64 * 1024)
#define MD_RESERVED_SECTORS (MD_RESERVED_BYTES / 512)
#define MD_NEW_SIZE_SECTORS(x) (((x) & ~(MD_RESERVED_SECTORS -1)) - MD_RESERVED_SECTORS)

It's safe to write the log after the MD superblock.

Regards,
Mike T.

Re: [dm-devel] [ANNOUNCE] multipath-tools-0.1.6

[Mike Tran]

On Tue, 2004-04-27 at 10:32, Mike Tran wrote:
> On Tue, 2004-04-27 at 05:09, thornber@redhat.com wrote:
> > On Tue, Apr 27, 2004 at 11:57:58AM +0200, christophe.varoqui@free.fr wrote:
> > > Selon thornber@redhat.com:
> > > 
> > > > On Sun, Apr 25, 2004 at 11:54:59PM +0200, christophe varoqui wrote:
> > > > > * add the dmadm WIP tool (read MD superblocks and create
> > > > >   corresponding devmaps when possible)
> > > > 
> > > > :)
> > > > 
> > > Any insight on where to put the log of the mirror target when mapping over a
> > > MD-created raid1 ?
> > 
> > MD effectively uses a log with a single region in it.  So we only need
> > 3 sectors (2 for the header 1 for the bitset) for the log, is there
> > any space in the MD metadata where this could be placed ?
> > 
> > - Joe
> 
> The MD device size is 64K aligned and MD superblock size is 4K.  In term
> of sectors, the calculation is as follows:

Oops.  I was thinking raid1 when saying : "The MD device size is 64K
aligned."  I should have said : "The new MD child size is 64K aligned."

Mike T.