[sheepdog-users] Sheepdog 0.9 missing live migration feature

[Liu Yuan]

On Mon, May 11, 2015 at 01:58:07PM +0200, Walid Moghrabi wrote:
> Hi,
> 
> > Sorry for keeping you waiting. I'll backport the patch tonight.
> 
> You're great :D
> 
> > Thanks a lot for your help. But I need to say that journaling and
> > object cache are unstable features. Please don't use them in
> > production.
> 
> Too bad :(
> I was really happy to try this on my setup, I equiped every node with a separated SSD drive on which I was wanting to store Sheepdog journal and/or object cache.
> Why are thse features "unstable" ?
> What are the risks ? In which conditions shouldn't I use them ?

Journaling won't be useful if you use object cache. Technically, journal is less
stable as object cache. Object cache is near mature so it is very reasonable to
make good use of object cache if you equip a dedicated SSD.

Just go ahead and stress object cache, if you meet any problem, please report
back and we'll try to fix it. In the past, we heavily ran object cache on our
prevoius production and no big problem found. But I have to admit, there might
be some corner case bugs around need to fix. I'd say that I'll shoot them down
if I aim at them :)

Thanks,
Yuan

> 
> Unless there is heavy risk, I think I'll still make a try (at least in my crash tests before moving the cluster to production) because it looks promising and anyway, Sheepdog is not considered stable until now and I'm using it with real joy since 0.6 even on production platform so ... ;)
> 
> Anyway, just for my wn curiosity, here is what I'm planning to do for my setup, I'd really appreciate any comment on it :
> 
> 9 nodes with each :
>   - 2 interfaces, one for cluster communication ("main" network) and one dedicated to Sheepdog's replication ("storage" network) with fixed IPs, completely closed and Jumbo frames enabled (mtu 9000)
>   - 3 600Gb SAS 15k dedicated hard drives that are not part of any RAID (standalone drives) that I was thinking using in MD mode
>   - 1 SSD SATA drive (on which the OS resides and that I was thinking to use for Sheepdog's journl and object cache)
> 
> So that means 27 hard drives cluster that I wanted to format using Erasure Code but until now, I don't really now which settings I'll configure for this ... I'd like to find the good balance between performances, security and storage space ... any proposition mostly welcomed.
> 
> 
> Regards
> 
> 
> ----- Mail original -----
> De: "Hitoshi Mitake" <mitake.hitoshi at gmail.com>
> À: "Walid Moghrabi" <walid.moghrabi at lezard-visuel.com>
> Cc: "Liu Yuan" <namei.unix at gmail.com>, "sheepdog-users" <sheepdog-users at lists.wpkg.org>
> Envoyé: Lundi 11 Mai 2015 12:52:21
> Objet: Re: [sheepdog-users] Sheepdog 0.9 missing live migration feature
> 
> Hi Walid,
> 
> On Mon, May 11, 2015 at 7:08 PM, Walid Moghrabi
> <walid.moghrabi at lezard-visuel.com> wrote:
> > Hi,
> >
> > Thanks for your information but I'm now building a whole new production cluster and I really need Live Migration to work.
> > You said you'll backport the locking patch so that it would re-enable live migration but the ProxMox "pve-sheepdog" package maintainer (packaged Sheepdog for the ProxMox distribution) didn't find the commit in the 0.9-stable branch.
> > I'd like to base my setup on Sheepdog as I really dislike Ceph for many reasons and this is the only no go point right now.
> > Would it be possible to push that commit and build a "0.9.2" ?
> > That would be great.
> 
> Sorry for keeping you waiting. I'll backport the patch tonight.
> 
> >
> > Many thanks in advance for your help.
> > I'd be happy to provide tests, benchmarks and whatever useful information you might want from this setup (I'll try to enable as much features as I can on this 9 nodes setup such ass SSD journaling, SSD object caching, multi-devices, Erasure Code, dedicated replication network, ...)
> 
> Thanks a lot for your help. But I need to say that journaling and
> object cache are unstable features. Please don't use them in
> production.
> 
> Thanks,
> Hitoshi
> 
> >
> > Best regards.
> >
> >
> > ----- Mail original -----
> > De: "Liu Yuan" <namei.unix at gmail.com>
> > À: "Walid Moghrabi" <walid.moghrabi at lezard-visuel.com>
> > Cc: "Hitoshi Mitake" <mitake.hitoshi at gmail.com>, "sheepdog-users" <sheepdog-users at lists.wpkg.org>
> > Envoyé: Vendredi 6 Mars 2015 04:33:22
> > Objet: Re: [sheepdog-users] Sheepdog 0.9 missing live migration feature
> >
> > On Thu, Mar 05, 2015 at 06:21:02PM +0100, Walid Moghrabi wrote:
> >> > Sorry for your inconvenience, Walid. I'll backport it to stable-0.9 later.
> >>
> >>
> >> Thank you for your kindness, don't worry, I'm not blaming anyone for this, I was just sad that this great feature was not available anymore but I'm happy to see there are plans to get it back again.
> >>
> >>
> >> Just a question : I rebuilt my cluster completely when upgrading to 0.9, once this patch is backported to the 0.9 branch, will I have to re-format again or will it be compatible as is ?
> >
> > I'm afraid you have re-format the cluster.
> >
> > Yuan