device mapper and resizing devices

device mapper and resizing devices

[Andy]

I am using dm-multipath on non-partitioned (xfs) devices on a SAN.  If I
resize the device, and rescan my path devices (i.e rescan /dev/sda,
/dev/sdb, /dev/sdc,/dev/sdd (all the same path)) the kernel sees the new
size of the individual devices, but the /sys/block/dm-0 device is still the
old size.  I believe this is the reason why I cannot grow my xfs filesystem
without doing a reboot so that the dm device will have the new size. I'd
like to avoid unmounting and rebooting to resize the device.  I haven't
played with lvm enough to feel comfortable using it.  Is there any way to
get the dm device to be the proper size, or is this a bug, or a feature that
needs further discussion?

Andy

Re: device mapper and resizing devices

[Arthur Bergman]

As far as I understand this is not supported. What we do is we add a 
new device, we then do sg_reset -b /dev/sgX and then we add them into 
the volume group and then we resize it.

I would also warn you that we have seen corruption repeatable times 
with xfs over devicemapper under 2.6.

Cheers
Arthur

-----
CTO @ Fotango Ltd
+447834716919
http://www.fotango.com/

On 1 Mar 2005, at 21:03, Andy wrote:

> I am using dm-multipath on non-partitioned (xfs) devices on a SAN.  If 
> I
> resize the device, and rescan my path devices (i.e rescan /dev/sda,
> /dev/sdb, /dev/sdc,/dev/sdd (all the same path)) the kernel sees the 
> new
> size of the individual devices, but the /sys/block/dm-0 device is 
> still the
> old size.  I believe this is the reason why I cannot grow my xfs 
> filesystem
> without doing a reboot so that the dm device will have the new size. 
> I'd
> like to avoid unmounting and rebooting to resize the device.  I haven't
> played with lvm enough to feel comfortable using it.  Is there any way 
> to
> get the dm device to be the proper size, or is this a bug, or a 
> feature that
> needs further discussion?
>
> Andy
>
> --
> dm-devel mailing list
> dm-devel@redhat.com
> https://www.redhat.com/mailman/listinfo/dm-devel

Re: device mapper and resizing devices

[christophe varoqui]

On Tue, 2005-03-01 at 15:03 -0600, Andy wrote:
>I am using dm-multipath on non-partitioned (xfs) devices on a SAN.  If I
>resize the device, and rescan my path devices (i.e rescan /dev/sda,
>/dev/sdb, /dev/sdc,/dev/sdd (all the same path)) the kernel sees the new
>size of the individual devices, but the /sys/block/dm-0 device is still the
>old size.  I believe this is the reason why I cannot grow my xfs filesystem
>without doing a reboot so that the dm device will have the new size. I'd
>like to avoid unmounting and rebooting to resize the device.  I haven't
>played with lvm enough to feel comfortable using it.  Is there any way to
>get the dm device to be the proper size, or is this a bug, or a feature that
>needs further discussion?
>

Runing "multipath" again, after rescans, should pick up the size change
and adjust the device map.

If not please report.

Regards,
-- 
christophe varoqui <christophe.varoqui@free.fr>

Re: device mapper and resizing devices

[Andy]

On Tue, Mar 01, 2005 at 11:20:43PM +0100, christophe varoqui wrote:
> On Tue, 2005-03-01 at 15:03 -0600, Andy wrote:
> >I am using dm-multipath on non-partitioned (xfs) devices on a SAN.  If I
> >resize the device, and rescan my path devices (i.e rescan /dev/sda,
> >/dev/sdb, /dev/sdc,/dev/sdd (all the same path)) the kernel sees the new
> >size of the individual devices, but the /sys/block/dm-0 device is still the
> >old size.  I believe this is the reason why I cannot grow my xfs filesystem
> >without doing a reboot so that the dm device will have the new size. I'd
> >like to avoid unmounting and rebooting to resize the device.  I haven't
> >played with lvm enough to feel comfortable using it.  Is there any way to
> >get the dm device to be the proper size, or is this a bug, or a feature that
> >needs further discussion?
> >
> 
> Runing "multipath" again, after rescans, should pick up the size change
> and adjust the device map.
> 
multipath does, and prints the new size, but it is unable to add the target
to the dm table because dev_size in device-mapper is still the smaller size
and I get the "device x:yy too small for target" message
(/sys/block/dm-x/size still shows the old size, even when everything else
has the new size).

Andy

 

Re: device mapper and resizing devices

[Arthur Bergman]

On 1 Mar 2005, at 22:20, christophe varoqui wrote:

>
> Runing "multipath" again, after rescans, should pick up the size change
> and adjust the device map.
>
> If not please report.
>
>

This hosed the my system pretty badly :-).

Cheers
Arthur

-----
CTO @ Fotango Ltd
+447834716919
http://www.fotango.com/