Re: stripped LV with segments vs one segment

lejeczek <peljasz@yahoo.co.uk> · Mon, 10 Apr 2017 12:16:18 +0100



    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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