[linux-lvm] stripped LV with segments vs one segment

[linux-lvm] stripped LV with segments vs one segment

[lejeczek]

hi there

I could not extend my stripped LV, had 3 stripes and wanted 
to add one more.
Only way LVM let me do it was where I ended up with this:

   --- Segments ---
   Logical extents 0 to 751169:
     Type        striped
     Stripes        3
     Stripe size        16.00 KiB
     Stripe 0:
       Physical volume    /dev/sdd
       Physical extents    0 to 250389
     Stripe 1:
       Physical volume    /dev/sde
       Physical extents    0 to 250389
     Stripe 2:
       Physical volume    /dev/sdc
       Physical extents    0 to 250389

   Logical extents 751170 to 1001559:
     Type        linear
     Physical volume    /dev/sdf
     Physical extents    0 to 250389

1st question - was this really the only way LVM would extend?
2nd - is there performance penalty with segments like above 
vs one stripped segment?

many thanks,
L.

Re: [linux-lvm] stripped LV with segments vs one segment

[Zdenek Kabelac]

Dne 10.4.2017 v 11:29 lejeczek napsal(a):
> hi there
>
> I could not extend my stripped LV, had 3 stripes and wanted to add one more.
> Only way LVM let me do it was where I ended up with this:
>
>   --- Segments ---
>   Logical extents 0 to 751169:
>     Type        striped
>     Stripes        3
>     Stripe size        16.00 KiB
>     Stripe 0:
>       Physical volume    /dev/sdd
>       Physical extents    0 to 250389
>     Stripe 1:
>       Physical volume    /dev/sde
>       Physical extents    0 to 250389
>     Stripe 2:
>       Physical volume    /dev/sdc
>       Physical extents    0 to 250389
>
>   Logical extents 751170 to 1001559:
>     Type        linear
>     Physical volume    /dev/sdf
>     Physical extents    0 to 250389
>
> 1st question - was this really the only way LVM would extend?
> 2nd - is there performance penalty with segments like above vs one stripped
> segment?
>

Hi


Not really sure what you aim to do.

If you have LV segment with 3 stripes - you have to keep also extension using 
3 stripes -  you can't  have 1st. halve of LV spanning 3 disk and add there a 
new LV segment as linear - as listed in this post.

Both segments must by striped.

Regards

Zdenek

Re: [linux-lvm] stripped LV with segments vs one segment

[lejeczek]

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On 10/04/17 12:03, Zdenek Kabelac wrote:
> Dne 10.4.2017 v 11:29 lejeczek napsal(a):
>> hi there
>>
>> I could not extend my stripped LV, had 3 stripes and 
>> wanted to add one more.
>> Only way LVM let me do it was where I ended up with this:
>>
>>   --- Segments ---
>>   Logical extents 0 to 751169:
>>     Type        striped
>>     Stripes        3
>>     Stripe size        16.00 KiB
>>     Stripe 0:
>>       Physical volume    /dev/sdd
>>       Physical extents    0 to 250389
>>     Stripe 1:
>>       Physical volume    /dev/sde
>>       Physical extents    0 to 250389
>>     Stripe 2:
>>       Physical volume    /dev/sdc
>>       Physical extents    0 to 250389
>>
>>   Logical extents 751170 to 1001559:
>>     Type        linear
>>     Physical volume    /dev/sdf
>>     Physical extents    0 to 250389
>>
>> 1st question - was this really the only way LVM would 
>> extend?
>> 2nd - is there performance penalty with segments like 
>> above vs one stripped
>> segment?
>>
>
> Hi
>
>
> Not really sure what you aim to do.
>
> If you have LV segment with 3 stripes - you have to keep 
> also extension using 3 stripes -  you can't  have 1st. 
> halve of LV spanning 3 disk and add there a new LV segment 
> as linear - as listed in this post.
>
> Both segments must by striped.
>
> Regards
>
> Zdenek

I had 3 stripe LV, you know, three PVs, and wanted the LV to 
have 4 stripes, wanted to add 4th PV, you can see it from 
above lvdisplay.
I tried these and each time it errored:
$ lvextend -v -i 4 -l+100%free dellH200.InternalB/0
$ lvextend -v -i 4 -l+100%pv dellH200.InternalB/0 /dev/sdf
$ lvextend -i 4 -l 100%vg dellH200.InternalB/0

I did have only one segment, an LV spanning 100%vg with 
100%each-pv.
And the above is the result of: $ lvextend -i 1 -l +100%free 
dellH200.InternalB/0 /dev/sdf

so, either I'm not getting it right or a stripped LV cannot 
be extended this way - then: is there performance penalty 
with segments like above vs one stripped
segment?




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Re: [linux-lvm] stripped LV with segments vs one segment

[Marian Csontos]

On 04/10/2017 01:16 PM, lejeczek wrote:

>
> I had 3 stripe LV, you know, three PVs, and wanted the LV to have 4
> stripes, wanted to add 4th PV, you can see it from above lvdisplay.

What you want is "reshape" not extend. This was committed as RAID 
feature to 2.02.169, but it is still somewhat experimental. You would 
need to convert stripe LV to RAID0 (aka takeover) and then reshape.

> I tried these and each time it errored:
> $ lvextend -v -i 4 -l+100%free dellH200.InternalB/0
> $ lvextend -v -i 4 -l+100%pv dellH200.InternalB/0 /dev/sdf
> $ lvextend -i 4 -l 100%vg dellH200.InternalB/0
>

lvextend With -i 4 this would add another striped segment with 4 devices 
after the first segment - and IIUC you do not have enough space for that.


> I did have only one segment, an LV spanning 100%vg with 100%each-pv.
> And the above is the result of: $ lvextend -i 1 -l +100%free
> dellH200.InternalB/0 /dev/sdf
>
> so, either I'm not getting it right or a stripped LV cannot be extended
> this way - then: is there performance penalty with segments like above
> vs one stripped
> segment?
>
>
>
>
>
>
> _______________________________________________
> linux-lvm mailing list
> linux-lvm@redhat.com
> https://www.redhat.com/mailman/listinfo/linux-lvm
> read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
>

Re: [linux-lvm] stripped LV with segments vs one segment

[lejeczek]

On 10/04/17 13:27, Marian Csontos wrote:
> On 04/10/2017 01:16 PM, lejeczek wrote:
>
>>
>> I had 3 stripe LV, you know, three PVs, and wanted the LV 
>> to have 4
>> stripes, wanted to add 4th PV, you can see it from above 
>> lvdisplay.
>
> What you want is "reshape" not extend. This was committed 
> as RAID feature to 2.02.169, but it is still somewhat 
> experimental. You would need to convert stripe LV to RAID0 
> (aka takeover) and then reshape.
>
thanks, I see it more clearly now.
Is it possible to get rid of that second segment now? Have 
the LV prior to extension?


>> I tried these and each time it errored:
>> $ lvextend -v -i 4 -l+100%free dellH200.InternalB/0
>> $ lvextend -v -i 4 -l+100%pv dellH200.InternalB/0 /dev/sdf
>> $ lvextend -i 4 -l 100%vg dellH200.InternalB/0
>>
>
> lvextend With -i 4 this would add another striped segment 
> with 4 devices after the first segment - and IIUC you do 
> not have enough space for that.
>
>
>> I did have only one segment, an LV spanning 100%vg with 
>> 100%each-pv.
>> And the above is the result of: $ lvextend -i 1 -l +100%free
>> dellH200.InternalB/0 /dev/sdf
>>
>> so, either I'm not getting it right or a stripped LV 
>> cannot be extended
>> this way - then: is there performance penalty with 
>> segments like above
>> vs one stripped
>> segment?
>>
>>
>>
>>
>>
>>
>> _______________________________________________
>> linux-lvm mailing list
>> linux-lvm@redhat.com
>> https://www.redhat.com/mailman/listinfo/linux-lvm
>> read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
>>
>
> _______________________________________________
> linux-lvm mailing list
> linux-lvm@redhat.com
> https://www.redhat.com/mailman/listinfo/linux-lvm
> read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/

Re: [linux-lvm] stripped LV with segments vs one segment

[Zdenek Kabelac]

Dne 10.4.2017 v 13:16 lejeczek napsal(a):
>
>
> On 10/04/17 12:03, Zdenek Kabelac wrote:
>> Dne 10.4.2017 v 11:29 lejeczek napsal(a):
>>> hi there
>>>
>>> I could not extend my stripped LV, had 3 stripes and wanted to add one more.
>>> Only way LVM let me do it was where I ended up with this:
>>>
>>>   --- Segments ---
>>>   Logical extents 0 to 751169:
>>>     Type        striped
>>>     Stripes        3
>>>     Stripe size        16.00 KiB
>>>     Stripe 0:
>>>       Physical volume    /dev/sdd
>>>       Physical extents    0 to 250389
>>>     Stripe 1:
>>>       Physical volume    /dev/sde
>>>       Physical extents    0 to 250389
>>>     Stripe 2:
>>>       Physical volume    /dev/sdc
>>>       Physical extents    0 to 250389
>>>
>>>   Logical extents 751170 to 1001559:
>>>     Type        linear
>>>     Physical volume    /dev/sdf
>>>     Physical extents    0 to 250389
>>>
>>> 1st question - was this really the only way LVM would extend?
>>> 2nd - is there performance penalty with segments like above vs one stripped
>>> segment?
>>>
>>
>> Hi
>>
>>
>> Not really sure what you aim to do.
>>
>> If you have LV segment with 3 stripes - you have to keep also extension
>> using 3 stripes -  you can't  have 1st. halve of LV spanning 3 disk and add
>> there a new LV segment as linear - as listed in this post.
>>
>> Both segments must by striped.
>>
>> Regards
>>
>> Zdenek
>
> I had 3 stripe LV, you know, three PVs, and wanted the LV to have 4 stripes,
> wanted to add 4th PV, you can see it from above lvdisplay.
> I tried these and each time it errored:
> $ lvextend -v -i 4 -l+100%free dellH200.InternalB/0
> $ lvextend -v -i 4 -l+100%pv dellH200.InternalB/0 /dev/sdf

You can't request stripe 4  (needs 4 disks)  and pass just single  /dev/sdf 
device.


Zdenek

Re: [linux-lvm] stripped LV with segments vs one segment

[lejeczek]

On 10/04/17 13:27, Marian Csontos wrote:
> On 04/10/2017 01:16 PM, lejeczek wrote:
>
>>
>> I had 3 stripe LV, you know, three PVs, and wanted the LV 
>> to have 4
>> stripes, wanted to add 4th PV, you can see it from above 
>> lvdisplay.
>
> What you want is "reshape" not extend. This was committed 
> as RAID feature to 2.02.169, but it is still somewhat 
> experimental. You would need to convert stripe LV to RAID0 
> (aka takeover) and then reshape.
>
convert from stipe to raid0 would not preserve stripe sizes? 
is this correct?
nor it would:

-I/--stripesize not allowed for LV dellH200.InternalB/0 when 
converting from striped to raid0.

   LVM version:     2.02.166(2)-RHEL7 (2016-11-16)
   Library version: 1.02.135-RHEL7 (2016-11-16)
   Driver version:  4.35.0

>> I tried these and each time it errored:
>> $ lvextend -v -i 4 -l+100%free dellH200.InternalB/0
>> $ lvextend -v -i 4 -l+100%pv dellH200.InternalB/0 /dev/sdf
>> $ lvextend -i 4 -l 100%vg dellH200.InternalB/0
>>
>
> lvextend With -i 4 this would add another striped segment 
> with 4 devices after the first segment - and IIUC you do 
> not have enough space for that.
>
>
>> I did have only one segment, an LV spanning 100%vg with 
>> 100%each-pv.
>> And the above is the result of: $ lvextend -i 1 -l +100%free
>> dellH200.InternalB/0 /dev/sdf
>>
>> so, either I'm not getting it right or a stripped LV 
>> cannot be extended
>> this way - then: is there performance penalty with 
>> segments like above
>> vs one stripped
>> segment?
>>
>>
>>
>>
>>
>>
>> _______________________________________________
>> linux-lvm mailing list
>> linux-lvm@redhat.com
>> https://www.redhat.com/mailman/listinfo/linux-lvm
>> read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
>>
>

Re: [linux-lvm] stripped LV with segments vs one segment

[Marian Csontos]

On 04/10/2017 03:35 PM, lejeczek wrote:
>
>
> On 10/04/17 13:27, Marian Csontos wrote:
>> On 04/10/2017 01:16 PM, lejeczek wrote:
>>
>>>
>>> I had 3 stripe LV, you know, three PVs, and wanted the LV to have 4
>>> stripes, wanted to add 4th PV, you can see it from above lvdisplay.
>>
>> What you want is "reshape" not extend. This was committed as RAID
>> feature to 2.02.169, but it is still somewhat experimental. You would
>> need to convert stripe LV to RAID0 (aka takeover) and then reshape.
>>
> thanks, I see it more clearly now.
> Is it possible to get rid of that second segment now? Have the LV prior
> to extension?

Either lvresize to previous size or vgcfgrestore would work UNLESS you 
resized the filesystem as well. vgcfgrestore has more limitations - no 
other metadata altering operations were performed on VG since the change.

Marian

Re: [linux-lvm] stripped LV with segments vs one segment

[Marian Csontos]

On 04/10/2017 04:27 PM, lejeczek wrote:
>
>
> On 10/04/17 13:27, Marian Csontos wrote:
>> On 04/10/2017 01:16 PM, lejeczek wrote:
>>
>>>
>>> I had 3 stripe LV, you know, three PVs, and wanted the LV to have 4
>>> stripes, wanted to add 4th PV, you can see it from above lvdisplay.
>>
>> What you want is "reshape" not extend. This was committed as RAID
>> feature to 2.02.169, but it is still somewhat experimental. You would
>> need to convert stripe LV to RAID0 (aka takeover) and then reshape.
>>
> convert from stipe to raid0 would not preserve stripe sizes? is this
> correct?

It should keep stripe size and if it does not it is a bug.

> nor it would:
>
> -I/--stripesize not allowed for LV dellH200.InternalB/0 when converting
> from striped to raid0.

As it says, the option is simply not allowed. Also it would be 
meaningless - one can not change stripe size while converting stripe to 
raid0. At least not in RHEL-7.3 (lvm2-2.02.166). This is supposed to 
work in upstream/2.02.169, but keep in mind that is a new feature, and 
it is altering data, so better keep a working backup.

>
>   LVM version:     2.02.166(2)-RHEL7 (2016-11-16)
>   Library version: 1.02.135-RHEL7 (2016-11-16)
>   Driver version:  4.35.0

Re: [linux-lvm] stripped LV with segments vs one segment

[lejeczek]

On 11/04/17 18:37, Marian Csontos wrote:
> On 04/10/2017 04:27 PM, lejeczek wrote:
>>
>>
>> On 10/04/17 13:27, Marian Csontos wrote:
>>> On 04/10/2017 01:16 PM, lejeczek wrote:
>>>
>>>>
>>>> I had 3 stripe LV, you know, three PVs, and wanted the 
>>>> LV to have 4
>>>> stripes, wanted to add 4th PV, you can see it from 
>>>> above lvdisplay.
>>>
>>> What you want is "reshape" not extend. This was 
>>> committed as RAID
>>> feature to 2.02.169, but it is still somewhat 
>>> experimental. You would
>>> need to convert stripe LV to RAID0 (aka takeover) and 
>>> then reshape.
>>>
>> convert from stipe to raid0 would not preserve stripe 
>> sizes? is this
>> correct?
>
> It should keep stripe size and if it does not it is a bug.
>
then probably a bug, I don't have it as was on the console 
in front of me now, but should be easy to replicate.
I had stripe LV with 16KB stripe and conversion(successful) 
to raid0 said I got 64KB stripe raid0 - is how I remember it.


>> nor it would:
>>
>> -I/--stripesize not allowed for LV dellH200.InternalB/0 
>> when converting
>> from striped to raid0.
>
> As it says, the option is simply not allowed. Also it 
> would be meaningless - one can not change stripe size 
> while converting stripe to raid0. At least not in RHEL-7.3 
> (lvm2-2.02.166). This is supposed to work in 
> upstream/2.02.169, but keep in mind that is a new feature, 
> and it is altering data, so better keep a working backup.
>
>>
>>   LVM version:     2.02.166(2)-RHEL7 (2016-11-16)
>>   Library version: 1.02.135-RHEL7 (2016-11-16)
>>   Driver version:  4.35.0
>