On Tue, Apr 28, 2015 at 7:52 AM, Gavin Ang <[email protected]> wrote:
> Hi, > > Thanks for all the inputs on this issue. I have limited hardware > options cause I am running this on a blade server which only has those 4 > slots for disks. Am using this in production too, so having redundant disks > means I have very little manouvering room. > You have two choice: 1) Listen to what we are saying and deploy SmartOS correctly and then enjoy all that it has to offer. 2) Don't listen to us and then try and fight SmartOS and then be met with nothing but disappointment. > Anyway, what I was trying to get at was the disparity between host > and guest io performance. Other posts like > http://serverfault.com/questions/425607/kvm-guest-io-is-much-slower-than-host-io-is-that-normal > point to qemu tuning of the disk caching mechanism. There are a lot more > tuning suggestions by IBM at > http://www-01.ibm.com/support/knowledgecenter/linuxonibm/liaat/liaatbpkvmguestcache.htm > so I think there is more I can do before resorting to disk changes. Also, > there is a IBM benchmark presentation at a linux conference (can’t find it > as I write this) which suggests that the kvm overhead for io can be less > than 15% of bare metal performance. > This issue has been asked and answered here with results proven and confirmed by many. With my SLOG device turned off, my disk performance in aa KVM instance is 10% of what it is with the KVM instance being turned on. One other thing to be aware of that isn't well documented: If you are using newer drives with 4k sector size, be really careful with raidz pools. I don't want to go into a long explanation here, but basically you will need to be careful with some of the disk and virtual disk related parameters. I can provide more insight if you are in that boat. > Seems like there is little documentation on how to tweak SmartOS > virtualization. I can see the place I would like to change in the smartvm > script, I just don’t know how to get it done because it seems like that > script is being generated when I issue the vmadm start $uuid command. > What do you mean by "tweak." Look at the vmadm man page and you will see that SmartOS offers all of the virtualization parameters any other hypervisor offers. There is no script. All of these parameters are set with configuration parameters in JSON format. I keep a set of vanilla JSON files for different types of VM containers in /opt/vms on the headnode. I'll modify these, then inject them into the vmadm create command like this. vmadm create -f windows_server.json. Once the vm containers have been creating, you have to follow the various update rules in the vmadm man page to update the vm container parameters. Some of the parameters cannnot be updated once the vm container has been created. > The guest machine I am trying to set up is for a database anyway, so > would be mostly sync writes, and looking at the literature out there, it > just seems that there must be a way to narrow the gap between the host and > the guest cause other OS can do it. I should be able to do it for smartOS > too. Question is HOW? > If it is a KVM container, it doesn't matter what the guest OS is doing. Your disk i/o of the guest OS is going to be horrible, probably in the range of 10% of the native zpool. The only way you can get by without a SLOG is by running OS VM containers. It sounds to me like you need to do a little more reading about SmartOS before you try and deploy it. There is a bit of a learning curve at first, but once you get over the initial hump you'll find SmartOS reasonably straight forward to administer. For reference, here is a sample JSON that I use for generic centos KVM instances: { "brand": "kvm", "alias" : "COS6_Min", "vcpus": 2, "autoboot": false, "ram": 1024, "disks": [ { "boot": true, "model": "virtio", "size": "10240", "block_size": 32768 } ], "nics": [ { "nic_tag": "admin", "model": "virtio", "ip": "dhcp", "allow_ip_spoofing": true, "primary": 1 } ] } ------------------------------------------- smartos-discuss Archives: https://www.listbox.com/member/archive/184463/=now RSS Feed: https://www.listbox.com/member/archive/rss/184463/25769125-55cfbc00 Modify Your Subscription: https://www.listbox.com/member/?member_id=25769125&id_secret=25769125-7688e9fb Powered by Listbox: http://www.listbox.com
