[pve-devel] less cores more iops / speed

Stefan Priebe - Profihost AG s.priebe at profihost.ag
Mon Nov 12 12:58:35 CET 2012


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
>



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