Re: hot scsi disk resize

[Fabien Salvi <fabien@cri74.org>]

Alex Tomas a écrit:
> Hello!
> 
> Here is patch to implement hot scsi resize function.
> Modern storage boxes support virtualization feature and
> may change logical volume size online. I think it would
> be great if linux supports such abilities. Look at
> this example:
> 
> root@zefir:# dmesg | tail
> scsi0:A:1:0: Tagged Queuing enabled.  Depth 32
> SCSI device sda: 2097152 512-byte hdwr sectors (1074 MB)
> SCSI device sda: drive cache: write through
>  sda: unknown partition table
> Attached scsi disk sda at scsi0, channel 0, id 1, lun 0
> 
> root@zefir:# mount -treiserfs /dev/sda /mnt
> 
> root@zefir:# df -Th
> Filesystem    Type    Size  Used Avail Use% Mounted on
> /dev/hda1     ext3    1.9G  1.8G  138M  93% /
> /dev/sda  reiserfs    1.0G   33M  991M   4% /mnt
> 
> root@zefir:# echo 'scsi rescan 0 0 1 0' >/proc/scsi/scsi 
> root@zefir:# dmesg|tail -n1
> SCSI device sda: 20971520 512-byte hdwr sectors (10737 MB)
> root@zefir:# resize_reiserfs /dev/sda 
> 
> <-------------resize_reiserfs, 2002------------->
> reiserfsprogs 3.6.4
> 
> root@zefir:# df -Th
> Filesystem    Type    Size  Used Avail Use% Mounted on
> /dev/hda1     ext3    1.9G  1.8G  138M  93% /
> /dev/sda  reiserfs     10G   33M  9.9G   1% /mnt

Well, I also think it's a very important and needed feature for HA systems.
I'm very interested in such things...

But, I thought resize_reiserfs only resize *unmounted* filesystem :
http://www.reiserfs.org/resize_reiserfs.html

Will it work under IO load ?

Reiserfs has a way to do it dynamically while using it, with mount option :
http://www.reiserfs.org/mount-options.html

I've tested this without a lot of success (I encounter a lot of problems).


I'm afraid that even if scsi subsystem support the resize option, 
FileSystems won't support it correctly...
Maybe with LVM ?

Did someone test it ?

-- 
Fabien SALVI      Centre de Ressources Informatiques
                   Archamps, France -- http://www.cri74.org
                   PingOO GNU/linux distribution : http://www.pingoo.org

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