[linux-lvm] lvextend does not change/fix stripes & stripesize for the whole LV?

lejeczek peljasz at yahoo.co.uk
Mon Mar 6 10:56:49 UTC 2017

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?


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