[pve-devel] [PATCH Storage] Newly created LVM volumes are now created with a number of stripes equal to the number of physical volumes in a volume group.

[Caspar Smit]

Hi,

Reading this I think there is another scenario that should be thought of:

I sometimes use a VG consisting of PV's which are unequal in size. For
instance a PV of 1TB and a second PV of 10TB.
If you are use striping on this VG (using auto detect number of PV's) the
result will be that you can only create 1TB worth of LV's on the VG.

Kind regards,
Caspar


Met vriendelijke groet,

Caspar Smit
Systemengineer
SuperNAS
Dorsvlegelstraat 13
1445 PA Purmerend

t: (+31) 299 410 414
e: casparsmit at supernas.eu
w: www.supernas.eu

2017-07-31 9:22 GMT+02:00 Tom Weber <pve at junkyard.4t2.com>:

> Am Sonntag, den 30.07.2017, 10:52 +0200 schrieb Martin Lablans:
> > Of course it would be preferable to leave this in the admin's hand
> > via
> > system-wide LVM configuration. This would also give Tom the
> > flexibility
> > for his setup. However, I don't know a way to achieve striping in
> > LVM
> > without using the -i option. raid_stripe_all_devices=1 does not
> > achieve
> > that result, cf. https://serverfault.com/questions/849088
> >
> > If someone knows how to configure striping in LVM, then I'll be happy
> > to
> > write a few lines for the Proxmox documentation or wiki. If not,
> > using
> > -i seems to be the only way to achieve striping.
> >
> > Basically, we are discussing to change the current behaviour from
> > "use 1
> > stripe" to "use <number of pvs> stripes". The latter option seems to
> > make a lot more sense to me, although I can see that there are
> > special
> > setups requiring exactly one stripe.
>
> I think huge (and affordable) Server SSDs and approaches like ceph etc.
> will move storage back from external solutions into the local servers
> again (hyper converged servers). And that will make local storage
> setups way more complex and maybe the rule (and my setups not so
> special anymore ;-) ).
>
> > I see three options:
> > 1) We find a way to configure that using LVM; I'll contribute
> > documentation
> > 2) We add a "-stripes" option to pct create, with options
> >       0       ==> old behaviour (no -i)
> >       n>0     ==> n stripes
> >       auto    ==> number of pvs
> > 3) Like 2), but define it as an option of the PVE storage
> > (/etc/pve/storage.cfg)
>
> I don't know what the design goals are for pve (still new to it) but I
> personally would prefer to have such an option well documented (with or
> without UI) over a (silent) default for the whole lvm setup.
> So i'd prefer 2) (maybe 3) but that will be difficult in complex
> setups).
>
> Regards,
>   Tom
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