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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.
gcc reports:
metadata/merge.c:229:58: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
metadata/merge.c:232:58: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
This patch allows users to create cache LVs with 'lvcreate'. An origin
or a cache pool LV must be created first. Then, while supplying the
origin or cache pool to the lvcreate command, the cache can be created.
Ex1:
Here the cache pool is created first, followed by the origin which will
be cached.
~> lvcreate --type cache_pool -L 500M -n cachepool vg /dev/small_n_fast
~> lvcreate --type cache -L 1G -n lv vg/cachepool /dev/large_n_slow
Ex2:
Here the origin is created first, followed by the cache pool - allowing
a cache LV to be created covering the origin.
~> lvcreate -L 1G -n lv vg /dev/large_n_slow
~> lvcreate --type cache -L 500M -n cachepool vg/lv /dev/small_n_fast
The code determines which type of LV was supplied (cache pool or origin)
by checking its type. It ensures the right argument was given by ensuring
that the origin is larger than the cache pool.
If the user wants to remove just the cache for an LV. They specify
the LV's associated cache pool when removing:
~> lvremove vg/cachepool
If the user wishes to remove the origin, but leave the cachepool to be
used for another LV, they specify the cache LV.
~> lvremove vg/lv
In order to remove it all, specify both LVs.
This patch also includes tests to create and remove cache pools and
cache LVs.
This patch allows the creation and removal of cache pools. Users are not
yet able to create cache LVs. They are only able to define the space used
for the cache and its characteristics (chunk_size and cache mode ATM) by
creating the cache pool.
When printing a message for the user and the lv_segment pointer is available,
use segtype->ops->name() instead of segtype->name. This gives a better
user-readable name for the segment. This is especially true for the
'striped' segment type, which prints "linear" if there is an area_count of
one.
Make limits for thin data_block_size and device_id part of public API.
FIXME: read them possible from some kernel header file in the future ?
But we may need to support different values for different versions ?
Implementation described in doc/lvm2-raid.txt.
Basic support includes:
- ability to create RAID 1/4/5/6 arrays
- ability to delete RAID arrays
- ability to display RAID arrays
Notable missing features (not included in this patch):
- ability to clean-up/repair failures
- ability to convert RAID segment types
- ability to monitor RAID segment types
Currently some operation with striped mirrors lead
to corrupted metadata, this patch just add detection of such
situation.
Example:
# lvcreate -i2 -l10 -n lvs vg_test
# lvconvert -m1 vg_test/lvs
# lvreduce -f -l1 vg_test/lvs
Reducing logical volume lvs to 4.00 MiB
Segment extent reduction 9not divisible by #stripes 2
Logical volume lvs successfully resized
# lvremove vg_test/lvs
Segment extent reduction 1not divisible by #stripes 2
LV segment lvs:0-4294967295 is incorrectly listed as being used by LV lvs_mimage_0
Internal error: LV segments corrupted in lvs_mimage_0.
Adding configure.in support for Replicators.
Adding basic lib lvm support for Replicators.
Adding flags REPLICATOR and REPLICATOR_LOG.
Adding segments SEG_REPLICATOR and SEG_REPLICATOR_DEV.
Adding basic methods for handling replicator metadata.
When moving parts of striped LVs, pvmove wouldn't care about leaving you with
two stripes on the same disk. Now --alloc anywhere is needed for that.
(Tried and gave up on two alternative approaches before the one committed here.)
Physical segments were still allocated from global
command context mempool.
This leads to very high memory usage when
activating large VG (vgchange).
(Memory usage was about 2G when >3000LVs).
Fix it by properly using vg->vgmem private pool,
so all the memory is released early.
New memory pool parameter is needed here for pv_split_segment
function.
Also fix the same problem in some minor allocations
(vg description, lv segment split).
