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"pvcreate_each_params" was a temporary name used
to transition from the old "pvcreate_params".
Remove the old pvcreate_params struct and rename the
new pvcreate_each_params struct to pvcreate_params.
Rename various pvcreate_each_params terms to simply
pvcreate_params.
Use the new pvcreate_each_device() function from
toollib, previously added for pvcreate, in place
of the old pvcreate_vol().
This also requires shifting the location where the
lock is acquired for the new VG name. The lock for
the new VG is supposed to be acquired before pvcreate.
This means splitting the vg_lock_newname() out of
vg_create(), and calling vg_lock_newname() directly
before pvcreate, and then calling the remainder of
vg_create() after pvcreate.
The new function vg_lock_and_create() now does
vg_lock_newname() + vg_create(), like the previous
version of vg_create().
The lock on the new VG name is released before the
pvcreate and reacquired after the pvcreate because
pvcreate needs to reset lvmcache, which doesn't work
when locks are held. An exception could likely be
made for the new VG name lock, which would allow
vgcreate to hold the new VG name lock across the
pvcreate step.
This is common code for handling PV create/remove
that can be shared by pvcreate/vgcreate/vgextend/pvremove.
This does not change any commands to use the new code.
- Pull out the hidden equivalent of process_each_pv
into an actual top level process_each_pv.
- Pull the prompts to the top level, and do not
run any prompts while locks are held.
The orphan lock is reacquired after any prompts are
done, and the devices being created are checked for
any change made while the lock was not held.
Previously, pvcreate_vol() was the shared function for
creating a PV for pvcreate, vgcreate, vgextend.
Now, it will be toollib function pvcreate_each_device().
pvcreate_vol() was called effectively as a helper, from
within vgcreate and vgextend code paths.
pvcreate_each_device() will be called at the same level
as other process_each functions.
One of the main problems with pvcreate_vol() is that
it included a hidden equivalent of process_each_pv for
each device being created:
pvcreate_vol() -> _pvcreate_check() ->
find_pv_by_name() -> get_pvs() ->
get_pvs_internal() -> _get_pvs() -> get_vgids() ->
/* equivalent to process_each_pv */
dm_list_iterate_items(vgids)
vg = vg_read_internal()
dm_list_iterate_items(&vg->pvs)
pvcreate_each_device() reorganizes the code so that
each-VG-each-PV loop is done once, and uses the standard
process_each_pv function at the top level of the function.
Fix lvm2app to return either 0 or 1 for lvm_vg_is_{clustered,exported},
including internal functions pvseg_is_allocated and vg_is_resizeable
which are not yet exposed in lvm2app but make them consistent with the
rest.
Add new test for lv_is_snapshot().
Also move few other bitchecks into same place as remaining bit tests.
TODO: drop lv_is_merging_origin() and keep using lv_is_merging().
This option could never have been printed in lvm2 metadata, so it could
be safely removed as it could have been set only as 0.
These configurable setting is supported via metadata profile.
Running "vgremove -f VG & pvs" results in the pvs
command reporting that the VG is not found or is
inconsistent. If the VG is gone or being removed,
the pvs command should just skip it and not print
errors about it.
"Not found" is because the pvs command created the
list of VGs to process, including VG, then vgremove
removed the VG, then the pvs command came to to read
the VG to process it and did not find it.
An "inconsistent" error could be reported if vgremove
had only partially completed removing VG when pvs did
vg_read on the VG to process it, causing pvs to find
the VG in a partially-removed state.
This fix adds a flag that pvs uses to ignore a VG
that can't be read or is inconsistent.
Certain stacks of cached LVs may have unexpected consequences.
So add a warning function called when LV is cached to detect
such caces and WARN user about them - the best we could do ATM.
Change logic and naming of some internal API functions.
cache_set_mode() and cache_set_policy() both take segment.
cache mode is now correctly 'masked-in'.
If the passed segment is 'cache' segment - it will automatically
try to find 'defaults' according to profiles if the are NOT
specified on command line or they are NOT already set for cache-pool.
These defaults are never set for cache-pool.
Keep policy name separate from policy settings and avoid
to mangling and demangling this string from same config tree.
Ensure policy_name is always defined.
There are two different failure conditions detected in
access_vg_lock_type() that should have different error
messages. This adds another failure flag so the two
cases can be distinguished to avoid printing a misleading
error message.
Just as 'e' means activation with an exclusive lock,
add an 's' to mean activation with a shared lock.
This allows the existing but implicit behavior of '-ay'
of clvm LVs to be specified explicitly. For local VGs,
asy simply means ay, just like aey means ay.
For local VGs, ay == aey == asy
For clvm VGs, ay == asy, aey == aey, asy == asy
In process_each_{vg,lv,pv} when no vgname args are given,
the first step is to get a list of all vgid/vgname on the
system. This is exactly what lvmetad returns from a
vg_list request. The current code is doing a vg_lookup
on each VG after the vg_list and populating lvmcache with
the info for each VG. These preliminary vg_lookup's are
unnecessary, because they will be done again when the
processing functions call vg_read. This patch eliminates
the initial round of vg_lookup's, which can roughly cut in
half the number of lvmetad requests and save a lot of extra work.
Do not keep dangling LVs if they're removed from the vg->lvs list and
move them to vg->removed_lvs instead (this is actually similar to already
existing vg->removed_pvs list, just it's for LVs now).
Once we have this vg->removed_lvs list indexed so it's possible to
do lookups for LVs quickly, we can remove the LV_REMOVED flag as
that one won't be needed anymore - instead of checking the flag,
we can directly check the vg->removed_lvs list if the LV is present
there or not and to say if the LV is removed or not then. For now,
we don't have this index, but it may be implemented in the future.
This avoids a problem in which we're using selection on LV list - we
need to do the selection on initial state and not on any intermediary
state as we process LVs one by one - some of the relations among LVs
can be gone during this processing.
For example, processing one LV can cause the other LVs to lose the
relation to this LV and hence they're not selectable anymore with
the original selection criteria as it would be if we did selection
on inital state. A perfect example is with thin snapshots:
$ lvs -o lv_name,origin,layout,role vg
LV Origin Layout Role
lvol1 thin,sparse public,origin,thinorigin,multithinorigin
lvol2 lvol1 thin,sparse public,snapshot,thinsnapshot
lvol3 lvol1 thin,sparse public,snapshot,thinsnapshot
pool thin,pool private
$ lvremove -ff -S 'lv_name=lvol1 || origin=lvol1'
Logical volume "lvol1" successfully removed
The lvremove command above was supposed to remove lvol1 as well as
all its snapshots which have origin=lvol1. It failed to do so, because
once we removed the origin lvol1, the lvol2 and lvol3 which were
snapshots before are not snapshots anymore - the relations change
as we're processing these LVs one by one.
If we do the selection first and then execute any concrete actions on
these LVs (which is what this patch does), the behaviour is correct
then - the selection is done on the *initial state*:
$ lvremove -ff -S 'lv_name=lvol1 || origin=lvol1'
Logical volume "lvol1" successfully removed
Logical volume "lvol2" successfully removed
Logical volume "lvol3" successfully removed
Similarly for all the other situations in which relations among
LVs are being changed by processing the LVs one by one.
This patch also introduces LV_REMOVED internal LV status flag
to mark removed LVs so they're not processed further when we
iterate over collected list of LVs to be processed.
Previously, when we iterated directly over vg->lvs list to
process the LVs, we relied on the fact that once the LV is removed,
it is also removed from the vg->lvs list we're iterating over.
But that was incorrect as we shouldn't remove LVs from the list
during one iteration while we're iterating over that exact list
(dm_list_iterate_items safe can handle only one removal at
one iteration anyway, so it can't be used here).
Refactor the recent metadata-reading optimisation patches.
Remove the recently-added cache fields from struct labeller
and struct format_instance.
Instead, introduce struct lvmcache_vgsummary to wrap the VG information
that lvmcache holds and add the metadata size and checksum to it.
Allow this VG summary information to be looked up by metadata size +
checksum. Adjust the debug log messages to make it clear when this
shortcut has been successful.
(This changes the optimisation slightly, and might be extendable
further.)
Add struct cached_vg_fmtdata to format-specific vg_read calls to
preserve state alongside the VG across separate calls and indicate
if the details supplied match, avoiding the need to read and
process the VG metadata again.
When reading VG mda from multiple PVs - do all the validation only
when mda is seen for the first time and when mda checksum and length
is same just return already existing VG pointer.
(i.e. using 300PVs for a VG would lead to create and destroy 300 config trees....)
Previous versions of lvm will not obey the restrictions
imposed by the new system_id, and would allow such a VG
to be written. So, a VG with a new system_id is further
changed to force previous lvm versions to treat it as
read-only. This is done by removing the WRITE flag from
the metadata status line of these VGs, and putting a new
WRITE_LOCKED flag in the flags line of the metadata.
Versions of lvm that recognize WRITE_LOCKED, also obey the
new system_id. For these lvm versions, WRITE_LOCKED is
identical to WRITE, and the rules associated with matching
system_id's are imposed.
A new VG lock_type field is also added that causes the same
WRITE/WRITE_LOCKED transformation when set. A previous
version of lvm will also see a VG with lock_type as read-only.
Versions of lvm that recognize WRITE_LOCKED, must also obey
the lock_type setting. Until the lock_type feature is added,
lvm will fail to read any VG with lock_type set and report an
error about an unsupported lock_type. Once the lock_type
feature is added, lvm will allow VGs with lock_type to be
used according to the rules imposed by the lock_type.
When both system_id and lock_type settings are removed, a VG
is written with the old WRITE status flag, and without the
new WRITE_LOCKED flag. This allows old versions of lvm to
use the VG as before.
Set ACCESS_NEEDS_SYSTEM_ID VG status flag whenever there is
a non-lvm1 system_id set. Prevents concurrent access from
older LVM2 versions.
Not set on VGs that bear a system_id only due to conversion
from lvm1 metadata.
cmirror uses the CPG library to pass messages around the cluster and maintain
its bitmaps. When a cluster mirror starts-up, it must send the current state
to any joining members - a checkpoint. When mirrors are large (or the region
size is small), the bitmap size can exceed the message limit of the CPG
library. When this happens, the CPG library returns CPG_ERR_TRY_AGAIN.
(This is also a bug in CPG, since the message will never be successfully sent.)
There is an outstanding bug (bug 682771) that is meant to lift this message
length restriction in CPG, but for now we work around the issue by increasing
the mirror region size. This limits the size of the bitmap and avoids any
issues we would otherwise have around checkpointing.
Since this issue only affects cluster mirrors, the region size adjustments
are only made on cluster mirrors. This patch handles cluster mirror issues
involving pvmove, lvconvert (from linear to mirror), and lvcreate. It also
ensures that when users convert a VG from single-machine to clustered, any
mirrors with too many regions (i.e. a bitmap that would be too large to
properly checkpoint) are trapped.
Move the lvm1 sys ID into vg->lvm1_system_id and reenable the #if 0
LVM1 code. Still display the new-style system ID in the same
reporting field, though, as only one can be set.
Add a format feature flag FMT_SYSTEM_ON_PVS for LVM1 and disallow
access to LVM1 VGs if a new-style system ID has been set.
Treat the new vg->system_id as const.
The previous patch felt short WRT disabling allocation on PVs holding other
legs of the RAID LV persistently; this patch introduces an internal,
transient PV flag PV_ALLOCATION_PROHIBITED to address this very problem.
General problem description for completeness:
An 'lvconvert --repair $RAID_LV" to replace a failed leg of a multi-segment
RAID10/4/5/6 logical volume can lead to allocation of (parts of) the replacement
image component pair on the physical volume of another image component
(e.g. image 0 allocated on the same PV as image 1 silently impeding resilience).
Patch fixes this severe resilince issue by prohibiting allocation on PVs
already holding other legs of the RAID set. It allows to allocate free space
on any operational PV already holding parts of the image component pair.
Support error_if_no_space feature for thin pools.
Report more info about thinpool status:
(out_of_data (D), metadata_read_only (M), failed (F) also as health
attribute.)
When creating/activating clustered mirrors, we should have cmirrord
available and running. If it's not, we ended up with rather cryptic
errors like:
$ lvcreate -l1 -m1 --type mirror vg
Error locking on node 1: device-mapper: reload ioctl on failed: Invalid argument
Failed to activate new LV.
$ vgchange -ay vg
Error locking on node node 1: device-mapper: reload ioctl on failed: Invalid argument
This patch adds check for cmirror availability and it errors out
properly, also giving a more precise error messge so users are able
to identify the source of the problem easily:
$ lvcreate -l1 -m1 --type mirror vg
Shared cluster mirrors are not available.
$ vgchange -ay vg
Error locking on node 1: Shared cluster mirrors are not available.
Exclusively activated cluster mirror LVs are OK even without cmirrord:
$ vgchange -aey vg
1 logical volume(s) in volume group "vg" now active
Failed recovery provides different (NULL) VG then FAILED_INCONSISTENT.
Mark it with different failure bit - since FAILED_INCONSISTENT is
supposed to contain something 'usable' (thought inconsistent).
Do not use 'any' policy name as a value in config tree - so we stick
with 'policy_settings' and extra 'policy_name' for libdm params.
Update lvm2 API as well.
Example of supported metadata:
policy = "mq"
policy_settings {
migration_threshold = 2048
sequential_threshold = 512
random_threshold = 4
read_promote_adjustment = 10
}
Replace lv_cache_block_info() and lv_cache_policy_info()
with lv_cache_status() which directly returns
dm_status_cache structure together with some calculated
values.
After use mem pool stored inside lv_status_cache structure
needs to be destroyed.
Add API call to calculate extents from percentage value.
Size is based in DM_PERCENT_1 units.
(Supporting decimal point number).
This commit is preparing functionality for more global
usage of % with i.e. --size option.
Move code for creation of thin volume into a single place
out of lv_extend(). This allows to drop extra pool arg
for alloc_lv_segment() && lv_extend() and makes code
more easier to read and follow.
Refactor lvcreate code.
Prefer to use arg_outside_list_is_set() so we get automatic 'white-list'
validation of supported options with different segment types.
Drop used lp->cache, lp->cache and use seg_is_cache(), seg_is_thin()
Draw clear border where is the last moment we could change create
segment type.
When segment type is given with --type - do not allow it to be changed
later.
Put together tests related to individual segment types.
Finish cache conversion at proper part of lv_manip code after
the vg_metadata are written - so we could correcly clean-up created
stripe LV for cache volume.
Introduce new option to specify pool data size.
This will be user to create i.e. cache & cachepool at once.
And possible for thin external origin snapshot.
This is only very basic patch to enable options, the
real working code will come later.
The warnings arg was used to enable logging of warnings
when reading a PV. This arg is turned into a set of flags
with the WARN_PV_READ flag matching the existing behavior.
A new flag WARN_INCONSISTENT is added that will cause
vg_read_internal() to log the "VG is not consistent"
warning so the various callers do not need to log
this warning themselves.
A new vg_read flag READ_WARN_INCONSISTENT is used from
reporting to enable the WARN_INCONSISTENT flag in
vg_read_internal.
[Committed by agk with cosmetic changes and tweaks.]
Introduce pool function for validation of chunk size.
It's good idea to be able to reject invalid chunk size
when entered on command line before we open VG.
The cache mode of a new cache pool is always explicitly
included in the vg metadata. If a cache mode is not
specified on the command line, the cache mode is taken
from lvm.conf allocation/cache_pool_cachemode, which
defaults to "writethrough".
The cache mode can be displayed with lvs -o+cachemode.
We use adjusted_mirror_region_size() in two different contexts.
Either on command line -
here we do want to inform user about reduction of size.
Or in pvmove activation context -
here we should only use 'verbose' info.
Try to enforce consistent macro usage along these lines:
lv_is_mirror - mirror that uses the original dm-raid1 implementation
(segment type "mirror")
lv_is_mirror_type - also includes internal mirror image and log LVs
lv_is_raid - raid volume that uses the new dm-raid implementation
(segment type "raid")
lv_is_raid_type - also includes internal raid image / log / metadata LVs
lv_is_mirrored - LV is mirrored using either kernel implementation
(excludes non-mirror modes like raid5 etc.)
lv_is_pvmove - internal pvmove volume
Use lv_is_* macros throughout the code base, introducing
lv_is_pvmove, lv_is_locked, lv_is_converting and lv_is_merging.
lv_is_mirror_type no longer includes pvmove.
Fix rename operation for snapshot (cow) LV.
Only the snapshot's origin has the lock and by mistake suspend
and resume has been called for the snapshot LV.
This further made volumes unusable in cluster.
So instead of suspend and resuming list of LVs,
we need to just suspend and resume origin.
As the sequence write/suspend/commit/resume
is widely used in lvm2 code base - move it to
new lv_update_and_reload function.
The 'lv_type' field name was a bit misleading. Better one is 'lv_role'
since this fields describes what's the actual use of the LV currently -
its 'role'.
Sort out the lvresize calculation code to handle size changes
specified as physical extents as well as logical extents
and to process mirror resizing and raid extensions correctly.
The 'approx alloc' option was masking the underlying problem.
The lv_type_name function is remnant from old code that reported
only single string for the LV type. LV types are now reported
in a more extended way as keyword list that describe the type
precisely (using lv_layout_and_type fn).
The lv_type_name was used in some error messages to display the
type of the LV so just reinstate the old messages back referencing
the type directly with a string - this is enough for error messages.
They don't need to display the LV type as precisely as it's used
on lvs output (which is optimized for selection anyway).
The lv_layout and lv_type fields together help with LV identification.
We can do basic identification using the lv_attr field which provides
very condensed view. In contrast to that, the new lv_layout and lv_type
fields provide more detialed information on exact layout and type used
for LVs.
For top-level LVs which are pure types not combined with any
other LV types, the lv_layout value is equal to lv_type value.
For non-top-level LVs which may be combined with other types,
the lv_layout describes the underlying layout used, while the
lv_type describes the use/type/usage of the LV.
These two new fields are both string lists so selection (-S/--select)
criteria can be defined using the list operators easily:
[] for strict matching
{} for subset matching.
For example, let's consider this:
$ lvs -a -o name,vg_name,lv_attr,layout,type
LV VG Attr Layout Type
[lvol1_pmspare] vg ewi------- linear metadata,pool,spare
pool vg twi-a-tz-- pool,thin pool,thin
[pool_tdata] vg rwi-aor--- level10,raid data,pool,thin
[pool_tdata_rimage_0] vg iwi-aor--- linear image,raid
[pool_tdata_rimage_1] vg iwi-aor--- linear image,raid
[pool_tdata_rimage_2] vg iwi-aor--- linear image,raid
[pool_tdata_rimage_3] vg iwi-aor--- linear image,raid
[pool_tdata_rmeta_0] vg ewi-aor--- linear metadata,raid
[pool_tdata_rmeta_1] vg ewi-aor--- linear metadata,raid
[pool_tdata_rmeta_2] vg ewi-aor--- linear metadata,raid
[pool_tdata_rmeta_3] vg ewi-aor--- linear metadata,raid
[pool_tmeta] vg ewi-aor--- level1,raid metadata,pool,thin
[pool_tmeta_rimage_0] vg iwi-aor--- linear image,raid
[pool_tmeta_rimage_1] vg iwi-aor--- linear image,raid
[pool_tmeta_rmeta_0] vg ewi-aor--- linear metadata,raid
[pool_tmeta_rmeta_1] vg ewi-aor--- linear metadata,raid
thin_snap1 vg Vwi---tz-k thin snapshot,thin
thin_snap2 vg Vwi---tz-k thin snapshot,thin
thin_vol1 vg Vwi-a-tz-- thin thin
thin_vol2 vg Vwi-a-tz-- thin multiple,origin,thin
Which is a situation with thin pool, thin volumes and thin snapshots.
We can see internal 'pool_tdata' volume that makes up thin pool has
actually a level10 raid layout and the internal 'pool_tmeta' has
level1 raid layout. Also, we can see that 'thin_snap1' and 'thin_snap2'
are both thin snapshots while 'thin_vol1' is thin origin (having
multiple snapshots).
Such reporting scheme provides much better base for selection criteria
in addition to providing more detailed information, for example:
$ lvs -a -o name,vg_name,lv_attr,layout,type -S 'type=metadata'
LV VG Attr Layout Type
[lvol1_pmspare] vg ewi------- linear metadata,pool,spare
[pool_tdata_rmeta_0] vg ewi-aor--- linear metadata,raid
[pool_tdata_rmeta_1] vg ewi-aor--- linear metadata,raid
[pool_tdata_rmeta_2] vg ewi-aor--- linear metadata,raid
[pool_tdata_rmeta_3] vg ewi-aor--- linear metadata,raid
[pool_tmeta] vg ewi-aor--- level1,raid metadata,pool,thin
[pool_tmeta_rmeta_0] vg ewi-aor--- linear metadata,raid
[pool_tmeta_rmeta_1] vg ewi-aor--- linear metadata,raid
(selected all LVs which are related to metadata of any type)
lvs -a -o name,vg_name,lv_attr,layout,type -S 'type={metadata,thin}'
LV VG Attr Layout Type
[pool_tmeta] vg ewi-aor--- level1,raid metadata,pool,thin
(selected all LVs which hold metadata related to thin)
lvs -a -o name,vg_name,lv_attr,layout,type -S 'type={thin,snapshot}'
LV VG Attr Layout Type
thin_snap1 vg Vwi---tz-k thin snapshot,thin
thin_snap2 vg Vwi---tz-k thin snapshot,thin
(selected all LVs which are thin snapshots)
lvs -a -o name,vg_name,lv_attr,layout,type -S 'layout=raid'
LV VG Attr Layout Type
[pool_tdata] vg rwi-aor--- level10,raid data,pool,thin
[pool_tmeta] vg ewi-aor--- level1,raid metadata,pool,thin
(selected all LVs with raid layout, any raid layout)
lvs -a -o name,vg_name,lv_attr,layout,type -S 'layout={raid,level1}'
LV VG Attr Layout Type
[pool_tmeta] vg ewi-aor--- level1,raid metadata,pool,thin
(selected all LVs with raid level1 layout exactly)
And so on...
Fix get_pool_params to only read params.
Add poolmetadataspare option to get_pool_params.
Move all profile code into update_pool_params.
Move recalculate code into pool_manip.c
The get_lv_type_name helps with translating volume type
to human readable form (can be used in reports or
various messages if needed).
The lv_is_linear and lv_is_striped complete the set of
lv_is_* functions that identify exact volume types.
Since vg_name inside /lib function has already been ignored mostly
except for a few debug prints - make it and official internal API
feature.
vg_name is used only in /tools while the VG is not yet openned,
and when lvresize/lvcreate /lib function is called with VG pointer
already being used, then vg_name becomes irrelevant (it's not been
validated anyway).
So any internal user of lvcreate_params and lvresize_params does not
need to set vg_name pointer and may leave it NULL.
pvmove can be used to move single LVs by name or multiple LVs that
lie within the specified PV range (e.g. /dev/sdb1:0-1000). When
moving more than one LV, the portions of those LVs that are in the
range to be moved are added to a new temporary pvmove LV. The LVs
then point to the range in the pvmove LV, rather than the PV
range.
Example 1:
We have two LVs in this example. After they were
created, the first LV was grown, yeilding two segments
in LV1. So, there are two LVs with a total of three
segments.
Before pvmove:
--------- --------- ---------
| LV1s0 | | LV2s0 | | LV1s1 |
--------- --------- ---------
| | |
-------------------------------------
PV | 000 - 255 | 256 - 511 | 512 - 767 |
-------------------------------------
After pvmove inserts the temporary pvmove LV:
--------- --------- ---------
| LV1s0 | | LV2s0 | | LV1s1 |
--------- --------- ---------
| | |
-------------------------------------
pvmove0 | seg 0 | seg 1 | seg 2 |
-------------------------------------
| | |
-------------------------------------
PV | 000 - 255 | 256 - 511 | 512 - 767 |
-------------------------------------
Each of the affected LV segments now point to a
range of blocks in the pvmove LV, which purposefully
corresponds to the segments moved from the original
LVs into the temporary pvmove LV.
The current implementation goes on from here to mirror the temporary
pvmove LV by segment. Further, as the pvmove LV is activated, only
one of its segments is actually mirrored (i.e. "moving") at a time.
The rest are either complete or not addressed yet. If the pvmove
is aborted, those segments that are completed will remain on the
destination and those that are not yet addressed or in the process
of moving will stay on the source PV. Thus, it is possible to have
a partially completed move - some LVs (or certain segments of LVs)
on the source PV and some on the destination.
Example 2:
What 'example 1' might look if it was half-way
through the move.
--------- --------- ---------
| LV1s0 | | LV2s0 | | LV1s1 |
--------- --------- ---------
| | |
-------------------------------------
pvmove0 | seg 0 | seg 1 | seg 2 |
-------------------------------------
| | |
| -------------------------
source PV | | 256 - 511 | 512 - 767 |
| -------------------------
| ||
-------------------------
dest PV | 000 - 255 | 256 - 511 |
-------------------------
This update allows the user to specify that they would like the
pvmove mirror created "by LV" rather than "by segment". That is,
the pvmove LV becomes an image in an encapsulating mirror along
with the allocated copy image.
Example 3:
A pvmove that is performed "by LV" rather than "by segment".
--------- ---------
| LV1s0 | | LV2s0 |
--------- ---------
| |
-------------------------
pvmove0 | * LV-level mirror * |
-------------------------
/ \
pvmove_mimage0 / pvmove_mimage1
------------------------- -------------------------
| seg 0 | seg 1 | | seg 0 | seg 1 |
------------------------- -------------------------
| | | |
------------------------- -------------------------
| 000 - 255 | 256 - 511 | | 000 - 255 | 256 - 511 |
------------------------- -------------------------
source PV dest PV
The thing that differentiates a pvmove done in this way and a simple
"up-convert" from linear to mirror is the preservation of the
distinct segments. A normal up-convert would simply allocate the
necessary space with no regard for segment boundaries. The pvmove
operation must preserve the segments because they are the critical
boundary between the segments of the LVs being moved. So, when the
pvmove copy image is allocated, all corresponding segments must be
allocated. The code that merges ajoining segments that are part of
the same LV when the metadata is written must also be avoided in
this case. This method of mirroring is unique enough to warrant its
own definitional macro, MIRROR_BY_SEGMENTED_LV. This joins the two
existing macros: MIRROR_BY_SEG (for original pvmove) and MIRROR_BY_LV
(for user created mirrors).
The advantages of performing pvmove in this way is that all of the
LVs affected can be moved together. It is an all-or-nothing approach
that leaves all LV segments on the source PV if the move is aborted.
Additionally, a mirror log can be used (in the future) to provide tracking
of progress; allowing the copy to continue where it left off in the event
there is a deactivation.
