* [linux-lvm] Convert striped lv to single pv on another disk?
@ 2012-12-13 13:32 Gianluca Cecchi
2012-12-13 15:28 ` Gianluca Cecchi
0 siblings, 1 reply; 6+ messages in thread
From: Gianluca Cecchi @ 2012-12-13 13:32 UTC (permalink / raw)
To: LVM general discussion and development
Hello,
I have a 300Gb LV composed by 2 150Gb each PV in striping:
lvdisplay:
--- Logical volume ---
LV Name /dev/VG_TEST/LV_TEST
VG Name VG_TEST
LV UUID 9LVrQr-XPSW-kuHt-eyYx-BrlE-MwQh-LcSfhN
LV Write Access read/write
LV Status available
# open 1
LV Size 299.99 GB
Current LE 76798
Segments 1
Allocation inherit
Read ahead sectors auto
- currently set to 512
Block device 253:61
lvdisplay --maps:
--- Logical volume ---
LV Name /dev/VG_TEST/LV_TEST
VG Name VG_TEST
LV UUID 9LVrQr-XPSW-kuHt-eyYx-BrlE-MwQh-LcSfhN
LV Write Access read/write
LV Status available
# open 1
LV Size 299.99 GB
Current LE 76798
Segments 1
Allocation inherit
Read ahead sectors auto
- currently set to 512
Block device 253:61
--- Segments ---
Logical extent 0 to 76797:
Type striped
Stripes 2
Stripe size 64 KB
Stripe 0:
Physical volume /dev/mapper/mpath133
Physical extents 0 to 38398
Stripe 1:
Physical volume /dev/mapper/mpath134
Physical extents 0 to 38398
I have to migrate to a single third 400Gb disk that I'm gong to
configure as a further PV of VG_TEST.
How can I pvmove a striped volume to a single one?
Thanks,
Gianluca
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [linux-lvm] Convert striped lv to single pv on another disk?
2012-12-13 13:32 [linux-lvm] Convert striped lv to single pv on another disk? Gianluca Cecchi
@ 2012-12-13 15:28 ` Gianluca Cecchi
2012-12-13 15:39 ` Bryn M. Reeves
0 siblings, 1 reply; 6+ messages in thread
From: Gianluca Cecchi @ 2012-12-13 15:28 UTC (permalink / raw)
To: LVM general discussion and development
Searching on Internet I found several methods and the one I tested (at
the moment only on loop devices) and seems ok is this one below, that
passes through creating a mirror between the initial striped lv
components and the new pv with lvconvert command and then gets rid off
the initial pvs
Just in case anyone else arrives here...
Gianluca
- working dir
cd /depot/test
- create pvs on file
[root@dep001 test]# time dd if=/dev/zero of=pv1 bs=1024k count=1024
same for pv2
# time dd if=/dev/zero of=pv1 bs=1024k count=1024
- setup loop devices
[root@dep001 test]# losetup -f /depot/test/pv1
[root@dep001 test]# losetup -f /depot/test/pv2
[root@dep001 test]# losetup -a
/dev/loop0: [fd00]:6029314 (/depot/test/pv1)
/dev/loop1: [fd00]:6029315 (/depot/test/pv2)
- create physical volumes
[root@dep001 test]# pvcreate /dev/loop0
Writing physical volume data to disk "/dev/loop0"
Physical volume "/dev/loop0" successfully created
[root@dep001 test]# pvcreate /dev/loop1
Writing physical volume data to disk "/dev/loop1"
Physical volume "/dev/loop1" successfully created
- create volume group
[root@dep001 test]# vgcreate vg_test /dev/loop0 /dev/loop1
/dev/cdrom: open failed: No medium found
Volume group "vg_test" successfully created
- create striped logical volume
[root@dep001 test]# lvcreate -i 2 -I 64k -n lv_test -l+100%FREE vg_test
Logical volume "lv_test" created
[root@dep001 test]# lvs -o name,size,stripes,stripesize vg_test/lv_test
LV LSize #Str Stripe
lv_test 1.99G 2 64.00K
- create third pv
[root@dep001 test]# time dd if=/dev/zero of=pvnew bs=1024k count=3076
and setup loop device
[root@dep001 test]# losetup -f /depot/test/pvnew
[root@dep001 test]# losetup -a
/dev/loop0: [fd00]:6029314 (/depot/test/pv1)
/dev/loop1: [fd00]:6029315 (/depot/test/pv2)
/dev/loop2: [fd00]:6029316 (/depot/test/pvnew)
- add new pv to vg
[root@dep001 test]# pvcreate /dev/loop2
[root@dep001 test]# vgextend vg_test /dev/loop2
- current situation
[root@dep001 test]# lvdisplay -m vg_test/lv_test
--- Logical volume ---
LV Name /dev/vg_test/lv_test
VG Name vg_test
LV UUID 0L3Dom-9frG-KeRU-mffe-lQaD-7UA2-AuuhNE
LV Write Access read/write
LV Status available
# open 0
LV Size 1.99 GB
Current LE 510
Segments 1
Allocation inherit
Read ahead sectors auto
- currently set to 512
Block device 253:4
--- Segments ---
Logical extent 0 to 509:
Type striped
Stripes 2
Stripe size 64 KB
Stripe 0:
Physical volume /dev/loop0
Physical extents 0 to 254
Stripe 1:
Physical volume /dev/loop1
Physical extents 0 to 254
[root@dep001 test]# pvs --segments -o+lv_name,seg_start_pe,segtype
/dev/loop0 /dev/loop1
PV VG Fmt Attr PSize PFree Start SSize LV Start Type
/dev/loop0 vg_test lvm2 a-- 1020.00M 0 0 255 lv_test 0 striped
/dev/loop1 vg_test lvm2 a-- 1020.00M 0 0 255 lv_test 0 striped
[root@dep001 test]# vgdisplay vg_test
--- Volume group ---
VG Name vg_test
System ID
Format lvm2
Metadata Areas 3
Metadata Sequence No 9
VG Access read/write
VG Status resizable
MAX LV 0
Cur LV 1
Open LV 0
Max PV 0
Cur PV 3
Act PV 3
VG Size 3.99 GB
PE Size 4.00 MB
Total PE 1021
Alloc PE / Size 510 / 1.99 GB
Free PE / Size 511 / 2.00 GB
VG UUID KSX0eT-mrPc-gRLb-w2tI-SOuj-VlaD-SMgFcc
- create mirror with new pv
[root@dep001 test]# lvconvert -m 1 /dev/vg_test/lv_test /dev/loop2
Insufficient suitable allocatable extents for logical volume : 510
more required
Unable to allocate extents for mirror(s).
the problem resides on the fact that by default it tries to use
another PV as mirror log
and we have no one...
So we use in memory mirror log with "--mirrorlog core" option
[root@dep001 test]# lvconvert -m 1 --mirrorlog core
/dev/vg_test/lv_test /dev/loop2
vg_test/lv_test: Converted: 0.2%
...
vg_test/lv_test: Converted: 92.2%
vg_test/lv_test: Converted: 93.5%
vg_test/lv_test: Converted: 100.0%
- keep off the striped leg
[root@dep001 test]# lvconvert -m 0 /dev/vg_test/lv_test /dev/loop0 /dev/loop1
Logical volume lv_test converted.
- verify new lv that is a linear one
[root@dep001 test]# lvdisplay vg_test/lv_test
--- Logical volume ---
LV Name /dev/vg_test/lv_test
VG Name vg_test
LV UUID 0L3Dom-9frG-KeRU-mffe-lQaD-7UA2-AuuhNE
LV Write Access read/write
LV Status available
# open 0
LV Size 1.99 GB
Current LE 510
Segments 1
Allocation inherit
Read ahead sectors auto
- currently set to 512
Block device 253:4
[root@dep001 test]# lvdisplay -m vg_test/lv_test
--- Logical volume ---
LV Name /dev/vg_test/lv_test
VG Name vg_test
LV UUID 0L3Dom-9frG-KeRU-mffe-lQaD-7UA2-AuuhNE
LV Write Access read/write
LV Status available
# open 0
LV Size 1.99 GB
Current LE 510
Segments 1
Allocation inherit
Read ahead sectors auto
- currently set to 512
Block device 253:4
--- Segments ---
Logical extent 0 to 509:
Type linear
Physical volume /dev/loop2
Physical extents 0 to 509
- keep off the old pvs
[root@dep001 test]# vgreduce vg_test /dev/loop0 /dev/loop1
Removed "/dev/loop0" from volume group "vg_test"
Removed "/dev/loop1" from volume group "vg_test"
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [linux-lvm] Convert striped lv to single pv on another disk?
2012-12-13 15:28 ` Gianluca Cecchi
@ 2012-12-13 15:39 ` Bryn M. Reeves
2012-12-13 16:11 ` Gianluca Cecchi
0 siblings, 1 reply; 6+ messages in thread
From: Bryn M. Reeves @ 2012-12-13 15:39 UTC (permalink / raw)
To: LVM general discussion and development; +Cc: Gianluca Cecchi
On 13/12/12 15:28, Gianluca Cecchi wrote:
> Searching on Internet I found several methods and the one I tested (at
> the moment only on loop devices) and seems ok is this one below, that
> passes through creating a mirror between the initial striped lv
> components and the new pv with lvconvert command and then gets rid off
> the initial pvs
Why not just use pvmove to move the extents off the two original PVs and
onto the third? The end result is the same (and internally it's not
dissimilar - pmove creates a temporary mirror volume to do its work) but
it's less manual work and should be more robust as pvmove does
checkpointing that allows the process to be interrupted and restarted.
Regards,
Bryn.
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [linux-lvm] Convert striped lv to single pv on another disk?
2012-12-13 15:39 ` Bryn M. Reeves
@ 2012-12-13 16:11 ` Gianluca Cecchi
2012-12-13 16:38 ` Bryn M. Reeves
0 siblings, 1 reply; 6+ messages in thread
From: Gianluca Cecchi @ 2012-12-13 16:11 UTC (permalink / raw)
To: Bryn M. Reeves; +Cc: LVM general discussion and development
On Thu, Dec 13, 2012 at 4:39 PM, Bryn M. Reeves wrote:
> On 13/12/12 15:28, Gianluca Cecchi wrote:
>> Searching on Internet I found several methods and the one I tested (at
>> the moment only on loop devices) and seems ok is this one below, that
>> passes through creating a mirror between the initial striped lv
>> components and the new pv with lvconvert command and then gets rid off
>> the initial pvs
>
> Why not just use pvmove to move the extents off the two original PVs and
> onto the third? The end result is the same (and internally it's not
> dissimilar - pmove creates a temporary mirror volume to do its work) but
> it's less manual work and should be more robust as pvmove does
> checkpointing that allows the process to be interrupted and restarted.
>
> Regards,
> Bryn.
>
>
I found in another thread that the resulting LV with pvmove remains a
striped one on only one disk as far as its structure is concerned...
with degraded performance...
Have you an example of pvmove command options to test to execute based
on my test?
So that I can verify with my loop devices?
Thanks
Gianluca
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [linux-lvm] Convert striped lv to single pv on another disk?
2012-12-13 16:11 ` Gianluca Cecchi
@ 2012-12-13 16:38 ` Bryn M. Reeves
2012-12-14 18:33 ` Stuart D Gathman
0 siblings, 1 reply; 6+ messages in thread
From: Bryn M. Reeves @ 2012-12-13 16:38 UTC (permalink / raw)
To: Gianluca Cecchi; +Cc: LVM general discussion and development
On 13/12/12 16:11, Gianluca Cecchi wrote:
> I found in another thread that the resulting LV with pvmove remains a
> striped one on only one disk as far as its structure is concerned...
> with degraded performance...
> Have you an example of pvmove command options to test to execute based
> on my test?
> So that I can verify with my loop devices?
Yes, you're right. You will end up with both stripes still present but
on a single disk.
The best I could do using pvmove was to move individual extents around
(!) to make the LV contiguous on-disk. Of course, this doesn't remove
the striping and inflates the number of segments since each pair of
striped extents effectively becomes a segment.
The lvconvert command also still accepts a -i <n> parameter but doesn't
do anything useful with it and doesn't report an error.
Regards,
Bryn.
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [linux-lvm] Convert striped lv to single pv on another disk?
2012-12-13 16:38 ` Bryn M. Reeves
@ 2012-12-14 18:33 ` Stuart D Gathman
0 siblings, 0 replies; 6+ messages in thread
From: Stuart D Gathman @ 2012-12-14 18:33 UTC (permalink / raw)
To: linux-lvm
On 12/13/2012 11:38 AM, Bryn M. Reeves expounded in part:
> On 13/12/12 16:11, Gianluca Cecchi wrote:
>> I found in another thread that the resulting LV with pvmove remains a
>> striped one on only one disk as far as its structure is concerned...
>> with degraded performance...
>> Have you an example of pvmove command options to test to execute based
>> on my test?
>> So that I can verify with my loop devices?
> Yes, you're right. You will end up with both stripes still present but
> on a single disk.
>
> The best I could do using pvmove was to move individual extents around
> (!) to make the LV contiguous on-disk. Of course, this doesn't remove
> the striping and inflates the number of segments since each pair of
> striped extents effectively becomes a segment.
>
> The lvconvert command also still accepts a -i <n> parameter but doesn't
> do anything useful with it and doesn't report an error.
>
Could you create an asymmetrical mirror - where one leg is striped and
the other is linear? Then you can just sync the mirror and delete the
striped leg. I could even see operating with such a mirror - call it
RAID �. Reads would prefer the striped side, and the mirror is there in
case one of the stripes fails, while requiring only 1 additional drive
and degrading only write performance.
RAID10 over the 3 drives is probably better, though.
^ permalink raw reply [flat|nested] 6+ messages in thread
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2012-12-13 13:32 [linux-lvm] Convert striped lv to single pv on another disk? Gianluca Cecchi
2012-12-13 15:28 ` Gianluca Cecchi
2012-12-13 15:39 ` Bryn M. Reeves
2012-12-13 16:11 ` Gianluca Cecchi
2012-12-13 16:38 ` Bryn M. Reeves
2012-12-14 18:33 ` Stuart D Gathman
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