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

[lejeczek]

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?



-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://listman.redhat.com/archives/linux-lvm/attachments/20170410/25aeac11/attachment.htm>