Re: lvextend does not change/fix stripes & stripesize for the whole LV?

lejeczek <peljasz@yahoo.co.uk> · Mon, 6 Mar 2017 10:56:49 +0000



    On 06/03/17 09:47, Zdenek Kabelac
      wrote:

    
    Dne 4.3.2017 v 14:58 lejeczek napsal(a):
      

      right?
        

        Or it does?
        

        From man pages my understanding is - it does not, an _expression_
        "the
        

        extension" is used there.
        

        If I have a LV with 2 stripes and 64KiB stripesizes, then adding
        two more
        

        stripes, like this:
        

        $ lvextend h300Int1/0 -i 2 -I 16 /dev/sd3 /dev/sd4 (if it was to
        succeed)
        

        will change the LV into 4 stripes LV, but what would happened to
        stripesize(s)?
        

      Hi
      

      At this moment lvm2 supports extension only of the same types.
      

      So extended/added segment will have some 'geometry' as the
      last/previous segment of your extended LV.
      

      So if you do not add any 'striping' parameters - they will be
      automatically detected from LV, if you add them - they will be
      compared and in case of mismatch operation will be rejected.
      

      Also if the allocation policy and free space in VG allows -
      extension will try first to extend existing segment before
      allocating new space somewhere else in VG.
      

      Regards
      

      Zdenek
      

    many! thanks

    may I share a comment - inasmuch as man pages for lvm are really
    good, there are places where some bits are missing.

    Take LVEXTEND, it speaks of --alloc but does not elaborate on it at
    all.

    Also says:

    --use-policies              Resizes the logical volume according to
    configured policy.  See  lvm.conf

    But I failed to find it there in lvm.conf.

    
    Would be great to have man pages completed with these missing bits.
    It's rhel 7.3, lvm2-2.02.166-1.el7_3.2.x86_64

    
    Ca I also ask you - reason I'm hoping I could downsize the
    stripesize is for I understand that with higher number of stripes
    stripesize could shrink so data(smaller files) would go to
    more(all?) stripes(increasing transfers speeds, phy devs are all
    SSDs in my case). Is my logic false here?

    
    And if it is not, would then creating a second LV(the same VG) with
    different(smaller) stripesize, then moving data over there, then
    removing the first LV and finally extending that "second" LV be a
    good, a correct way?

    
    b.w.

    L

    
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