[pve-devel] less cores more iops / speed

[Stefan Priebe - Profihost AG]

Am 12.11.2012 13:49, schrieb Alexandre DERUMIER:
>>> One VM on one Host: 18.000 IOP/s
>>> Two VM on one Host: 2x11.000 IOP/s
>>> Three VM on one Host: 3x7.000 IOP/s
>
> And host cpu is 100% ?

No. For three VMs yes. For one and two no. I think librbd / rbd 
implementation in kvm is the bottleneck here.

Stefan

> ----- Mail original -----
>
> De: "Stefan Priebe - Profihost AG" <s.priebe at profihost.ag>
> À: "Alexandre DERUMIER" <aderumier at odiso.com>
> Cc: "eric" <eric at netwalk.com>, pve-devel at pve.proxmox.com
> Envoyé: Lundi 12 Novembre 2012 12:58:35
> Objet: Re: [pve-devel] less cores more iops / speed
>
> Am 12.11.2012 08:51, schrieb Alexandre DERUMIER:
>>>> Right now RBD in KVM is limited by CPU speed.
>>
>> Good to known, so it's seem lack of threading, or maybe somes locks. (so faster cpu give more iops).
>>
>> If you lauch parallel fio on same host on different guest, do you get more total iops ? (for me it's scale)
>
> One VM on one Host: 18.000 IOP/s
> Two VM on one Host: 2x11.000 IOP/s
> Three VM on one Host: 3x7.000 IOP/s
>
>> if you launch 2 parallel fio, on same guest (on differents disk), do you get more iops ? (for me, it doesn't scale, so raid0 in guest doesn't help).
> No it doesn't scale.
>
> Stefan
>
>> ----- Mail original -----
>>
>> De: "Stefan Priebe" <s.priebe at profihost.ag>
>> À: "Alexandre DERUMIER" <aderumier at odiso.com>
>> Cc: "eric" <eric at netwalk.com>, pve-devel at pve.proxmox.com
>> Envoyé: Dimanche 11 Novembre 2012 13:07:36
>> Objet: Re: [pve-devel] less cores more iops / speed
>>
>> Am 11.11.2012 12:12, schrieb Alexandre DERUMIER:
>>> If I remember good, stefan can achieve 100.000 iops with iscsi with same kvm host.
>>
>> Correct but this was always with scsi-generic and I/O multipathing on
>> host. rbd does not support scsi-generic ;-(
>>
>>> I have checked ceph mailing, stefan seem to have resolved his problem with dual core with bios update !
>> Correct. So speed on Dual Xeon is now 14.000 IOP/s and 18.000 IOP/s on
>> Single Xeon. But the difference is an issue of the CPU Speed. 3,6Ghz
>> Single Xeon vs. 2.5Ghz Dual Xeon.
>>
>> Right now RBD in KVM is limited by CPU speed.
>>
>> Greets,
>> Stefan
>>