I think I didn’t make it clear. Those 10 hosts are all Gen8 blades, that’s why I want them to form a pool of their own. New Gen9 blades will go into a different pool.
On 3/9/16, 10:14 AM, "Tim Mackey" <tmac...@gmail.com> wrote: >In that case, Yiping, I would *definitely* recommend putting those servers >into at least two pools. The processors used in Gen8 and Gen9 servers can >not currently be joined into the same pool, and you actually need to be >very sensitive to the processor steppings. Dundee should fix that, but no >current version of CloudStack supports Dundee (and neither does Citrix at >the moment). > >-tim > >On Wed, Mar 9, 2016 at 12:38 PM, Yiping Zhang <yzh...@marketo.com> wrote: > >> Hi, Tim: >> >> Thanks for very detailed reply. >> >> These are Gen8 HP blades and all my new servers will be Gen9. That’s why >> I’d like to combine them into one maxed out cluster. I have only two guest >> VLAN’s and roughly 400 VM instances for this 10 hosts cluster. So I think >> performance wise I should be OK. >> >> Yiping >> >> >> >> On 3/8/16, 4:28 PM, "Tim Mackey" <tmac...@gmail.com> wrote: >> >> >Yiping, >> > >> >Here's the detailed answer .... >> > >> >From the XenServer perspective, there are a number of factors which go >> into >> >how various configuration limits are arrived at. Most of the time, they >> >aren't hard limits (for example I know of users with more than 16 hosts in >> >a pool). What the XenServer team do is for a given metric they determine >> >the point at which overall scalability is reduced to a target threshold. >> >That then becomes the "configuration limit" for a given release, and we >> >retest with every version. >> > >> >In the case of the "hosts per pool" limit, we need to ensure that all >> >operations we have can be performed without impairment with a given number >> >of hosts in a pool. We've kept the same maximum number of hosts in a pool >> >for a very long time (close to ten years so far), and that's a direct >> >reflection of how much we've increased individual host scalability. >> > >> >From a CloudStack perspective, there have been a number of serious scale >> >limits which have pushed XenServer. Hundreds of VLANs is one example that >> >Ahmad cites, but its also a case of the number of VMs and needing to >> manage >> >all those VM objects. iirc, the eight host recommendation came from some >> >large deployment requirements. If you don't have a need for 100s of VLANs >> >per pool, or aren't running 100s of VMs per host, you likely will be able >> >to get more than eight hosts per pool. >> > >> >From an operations perspective, I would look closely at your pool size and >> >ask the question of why you want to such a large pool. I'd argue having >> >two pools of five hosts is more efficient in CloudStack than a single pool >> >of ten hosts, plus if something should happen to one pool, the remaining >> >pool will continue to be available. CloudStack is very efficient at >> >managing resource pools, so many of the reasons traditional server admins >> >cite for wanting large pool sizes aren't as relevant in CloudStack. >> > >> >Of particular note is how you scale. With a ten host pool size, that's >> your >> >scalability block size, so as you grow you'll want to increase capacity in >> >chunks of ten hosts. With a smaller pool size, you'd be able to add >> >capacity in much smaller chunks. >> > >> >-tim >> > >> >On Tue, Mar 8, 2016 at 5:24 PM, Ahmad Emneina <aemne...@gmail.com> wrote: >> > >> >> IIRC, its just a recommendation. I think it stemmed from performance >> >> impact, due to numerous VLAN's present, in environments with lots of >> >> tenants. >> >> >> >> On Tue, Mar 8, 2016 at 2:10 PM, Yiping Zhang <yzh...@marketo.com> >> wrote: >> >> >> >> > Hi, all: >> >> > >> >> > The CloudStack doc recommends that for XenServer, do not put more >> than 8 >> >> > hosts in a cluster, while the Citrix XenServer doc says that XenServer >> >> 6.5 >> >> > can natively support 16 hosts in a cluster (resource pool). >> >> > >> >> > I am wondering why CloudStack is recommending a smaller cluster size >> than >> >> > that XenServer can natively support? If I create a cluster with 10 >> >> > XenServers, what could go wrong for me ? Has any one tried with CS >> >> cluster >> >> > with >8 XenServer hosts ? >> >> > >> >> > My environment is CS 4.5.1 (soon to be upgraded to 4.8.0) on RHEL 6.7 >> and >> >> > XenServer 6.5, using NetApp volumes for both primary and secondary >> >> storages. >> >> > >> >> > Yiping >> >> > >> >> >>
