[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?
>>
>>
>>
>>
>>
>>
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>>
>