On 2012-11-08 4:43, Edward Ned Harvey (opensolarisisdeadlongliveopensolaris) wrote:
> When I said performance was abysmal, I meant, if you dig right down and pressure the system for throughput to disk, you've got a Linux or Windows VM isnide of ESX, which is writing to a virtual disk, which ESX is then wrapping up inside NFS and TCP, talking on the virtual LAN to the ZFS server, which unwraps the TCP and NFS, pushes it all through the ZFS/Zpool layer, writing back to the virtual disk that ESX gave it, which is itself a layer on top of Ext3, before it finally hits disk. Based purely on CPU and memory throughput, my VM guests were seeing a max throughput of around 2-3 Gbit/sec. That's not *horrible* abysmal. But it's bad to be CPU/memory/bus limited if you can just eliminate all those extra layers, and do the virtualization directly isnide a system that supports zfs. Hi I have some experience with Virtualisation, mainly using Xen and KVM, but not much. I am just wondering why you export the ZFS system through NFS? I have had much better results (albeit spending more time setting up) using iSCSI. I found that performance was much better, I believe because a layer was being cut out of the loop. Rather than the hypervisor having to emulate block storage from files on NFS, the block storage is exposed directly from Solaris (in my case) through iSCSI, and passed through the virtual LAN to the other guests. The hypervisor then sees nothing but ethernet packets. This was a few years ago and I can't remember the numbers, but CPU consumption was drastically reduced and performance of the guests was increased significantly. The only downside was a slightly more complicated setup for the guests, but not by enough to sacrifice the performance benefits. It is possible that this is not the case in ESXi, or that more modern hypervisors deal with it more efficiently. That's why I'm asking the question :)
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