<html> <head> <meta http-equiv="Content-Type" content="text/html; charset=us-ascii"> <meta name="Generator" content="Microsoft Exchange Server"> <style></style> </head> <body> <div> <div id="x_compose-container" itemscope="" itemtype="https://schema.org/EmailMessage" style="direction:ltr"> <span itemprop="creator" itemscope="" itemtype="https://schema.org/Organization"><span itemprop="name"></span></span> <div> <div style="direction:ltr">Hello David,</div> <div><br> </div> <div style="direction:ltr">Yes I can specify most of the details in the lvcreate, however it is sad that I have to. There are multiple abstraction layers in lvm and I cannot set up a volume group which uses a allocation policy to distribute the volumes over all PV and stripe by default. And it would be even harder when striping to a subset of volumes.</div> <div><br> </div> <div style="direction:ltr">I have to make changes to the client code (in my case Nova's lvm driver) to get a better result. And if I would want to distribute the start segment over physical volumes I would have to add code to actually enumerate them and pick one at random. I had hoped to avoid this. (The next step would be to write DM tables myself...)</div> <div><br> </div> <div style="direction:ltr">In the Nova case the modules are very dynamically created and destroyed, so hand tuning is not an option here.</div> <div><br> </div> <div class="x_acompli_signature">Gruss<br> Bernd<br> -- <br> <a dir="ltr" href="http://bernd.eckenfels.net">http://bernd.eckenfels.net</a></div> </div> </div> <hr tabindex="-1" style="display:inline-block; width:98%"> <div id="x_divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" color="#000000" style="font-size:11pt"><b>From:</b> David Teigland <teigland@redhat.com><br> <b>Sent:</b> Wednesday, May 10, 2017 6:58:40 PM<br> <b>To:</b> Bernd<br> <b>Cc:</b> linux-lvm@redhat.com<br> <b>Subject:</b> Re: [linux-lvm] lvm/openstack: stripe all volumes and distribute them round robin on PVs</font> <div> </div> </div> </div> <font size="2"><span style="font-size:10pt;"> <div class="PlainText">On Wed, May 10, 2017 at 01:13:37PM +0200, Bernd wrote:<br> > Hello,<br> > <br> > when using local lvm2 logical volumes for OpenStack Nova ephemeral pool<br> > then the created logical volumes are linear (not striped) and what is worse<br> > than that, all volumes are allocated on the same first physical volume<br> > (until it is filled up).<br> > <br> > I made a ServerFault question about that:<br> > <br> > <a href="https://serverfault.com/questions/849088/automatically-distribute-lvm-stripes-for-specific-lvm2-vg-on-linux/849255#849255"> https://serverfault.com/questions/849088/automatically-distribute-lvm-stripes-for-specific-lvm2-vg-on-linux/849255#849255</a><br> > <br> > It was suggested that raid_stripe_all_devices should help (to turn on<br> > striping by default), but it did not. So I went ahead and patched the<br> > lvm.py of nova to turn the striping on. However I still wonder if there is<br> > a lvm option (allocation policy for that).<br> > <br> > Besides that, it looks like it is still creating the first stripe on the<br> > first device. It would make more sense to have it (even in the linear case)<br> > to round robin the LVs. Because first of all it might be the most busy part<br> > of the volume and secondly it helps for keeping room for expanding volumes.<br> > <br> > Is there anything planned in this direction?<br> <br> If you're concerned with placement of LVs on PVs, I'd probably skip<br> striping and add some logic specifying different PVs directly:<br> <br> lvcreate -n name -L size VG PV ...<br> <br> means the LV will be created using only the specified PVs.<br> <br> </div> </span></font> </body> </html>