[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?
>
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