[pve-devel] Storage migration: RFC

[Michael Rasmussen]

Hi all,

I have designed the conceptual solution for off-line storage migration
as can be read below (Also attached for better readability). Every
usecase have been tested from the command line and found working. Do
you have any comments or have I left something out?

Storage migration

Two distinct usecases - offline and online.
Four storage backend - raw, qcow2 and vmdk.
Two distinct environments - NFS and iSCSI(LVM).
Implementation preserves the machine on its current node.

Requirements: Since proxmox does not provide thin provisioning space
requirements are absolute so provided storage is available when initial
actions takes place we can initiate storage migration.

iSCSI: raw
NFS: raw, qcow2 and vmdk

iSCSI -> NFS
0) lvchange -ay $class->path($scfg, $volnamesrc)
1) lvchange -p r $class->path($scfg, $volnamesrc)
2) mkdir -p $class->path($scfg, $volnamedest)
     exception dir_exists: error if not empty
     exception could_not_create: error
3) qemu-img convert -p -O $class->format($scfg) $class->path($scfg,
$volnamesrc) "$class->path($scfg, $volnamedest).$class->format($scfg)"
     exception could_not_create: error
     exception no_more_space: - rm -f "$class->path($scfg,
$volnamedest).$class->format($scfg)"
                              - error
4) $class->device($scfg, $volnamesrc): "$class->path($scfg,
$volnamedest).$class->format($scfg)", cache=$class->cache($scfg,
$volnamesrc), $class->size($scfg, $volnamesrc) exception write_error: -
rm -f "$class->path($scfg, $volnamedest).$class->format($scfg)"
                            - error
5) lvremove -f $class->path($scfg, $volnamesrc)

   error:
      - lvchange -p rw $class->path($scfg, $volnamesrc)
      - lvchange -an $class->path($scfg, $volnamesrc)

iSCSI -> iSCSI
0) lvchange -ay $class->path($scfg, $volnamesrc)
1) lvchange -p r $class->path($scfg, $volnamesrc)
2) lvcreate -L $class->size($scfg, $volnamesrc) -n $class->name($scfg)
$class->storage($scfg, $volnamedest) exception could_not_create: error
3) dd if=$class->path($scfg, $volnamesrc) of=$class->path($scfg,
$volnamedest) bs=1M exception could_not_create: - lvremove -f
$class->path($scfg, $volnamedest)
                                 - error
4) $class->device($scfg, $volnamesrc): $class->path($scfg,
$volnamedest), cache=$class->cache($scfg, $volnamesrc),
$class->size($scfg, $volnamesrc) exception write_error: - lvremove -f
$class->path($scfg, $volnamedest)
                            - error
5) lvremove -f $class->path($scfg, $volnamesrc)

   error:
      - lvchange -p rw $class->path($scfg, $volnamesrc)
      - lvchange -an $class->path($scfg, $volnamesrc)

NFS -> iSCSI
0) chattr +i $class->path($scfg, $volnamesrc)
1) lvcreate -L $class->size($scfg, $volnamesrc) -n $class->name($scfg)
$class->storage($scfg, $volnamedest) exception could_not_create: error
2) dd if=$class->path($scfg, $volnamesrc) of=$class->path($scfg,
$volnamedest) bs=1M exception could_not_create: - lvremove -f
$class->path($scfg, $volnamedest)
                                 - error
3) $class->device($scfg, $volnamesrc): "$class->path($scfg,
$volnamedest).$class->format($scfg)", cache=$class->cache($scfg,
$volnamesrc), $class->size($scfg, $volnamesrc) exception write_error: -
lvremove -f $class->path($scfg, $volnamedest)
                            - error
4) chattr -i $class->path($scfg, $volnamesrc)
5) rm -f $class->path($scfg, $volnamesrc)

   error:
      - chattr -i $class->path($scfg, $volnamesrc)

NFS -> NFS
0) chattr +i $class->path($scfg, $volnamesrc)
1) mkdir -p $class->path($scfg, $volnamedest)
     exception dir_exists: error if not empty
     exception could_not_create: error
2) dd if=$class->path($scfg, $volnamesrc) of=$class->path($scfg,
$volnamedest) bs=1M exception could_not_create: error
3) $class->device($scfg, $volnamesrc): "$class->path($scfg,
$volnamedest).$class->format($scfg)", cache=$class->cache($scfg,
$volnamesrc), $class->size($scfg, $volnamesrc) exception write_error: -
rm -f "$class->path($scfg, $volnamedest).$class->format($scfg)"
                            - error
4) chattr -i $class->path($scfg, $volnamesrc)
5) rm -f $class->path($scfg, $volnamesrc)

   error:
      - chattr -i $class->path($scfg, $volnamesrc)


PS. Does the current API contain any utility for changing a vm.conf?

-- 
Hilsen/Regards
Michael Rasmussen

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