For those propeller heads who wants to know what a SLAT is, read on….

SLAT stands for “Second Level Address Translation”. SLAT is a new feature in today’s CPU on top of Virtualization support (Intel-V, AMD-V etc) to improve VM performance while reducing processing load on the hypervisor by removing the need for the hypervisor to maintain shadow page tables for each VM mapping virtual memory to physical memory.

So, ever thought about what happens when you move or migrate a VM from a host with SLAT support to another one without?

Answer is “Nothing”. You’ll obviously notice a slight performance degradation due to higher overhead on the receiving hosts’ hypervisor, but there won’t be any impact on its functionality.

Haven’t you heard about chimney which work as an exhaust in traditional Kitchens and factories?

Now one of the virtual networking features of Hyper-V in Windows Server 2008 R2 is using this word as “VM Chimney” - may be MS wants to emphasize that you got an easy path to flow. Anyway, VM Chimney in Hyper-V allows a VM to offload its network processing load onto the NIC of the host computer. This is something similar to TCP offload scenario, Hyper-V simply extends this functionality into the virtual world. This benefits both CPU and overall network throughput performance, and it is fully supported by Live Migration.

VM Chimney is disabled by default in Windows Server 2008 R2, primarily for compatibility reasons. Vendors like Intel, supports the compatibility for VM Chimney and if you are sure that the hardware you purchased support this – TURN IT ON for a better host system performance and a simultaneous boost to VM network throughput.

Support for Jumbo Frames was first introduced in initial release of Windows Server 2008 to support the hardware and now the same has been extended to support VMs. So, just like improving performance on hardware level, Jumbo Frame capability for VMs now can increase the performance of virtual networking and provides 6 times larger payloads per packet, which improves not only overall throughput but also reduces CPU utilization for large file transfers.

We know there has been a lot of work done or being done to make customers attract and adopt virtualization to make the environment green. To augment that, the upcoming release of Microsoft's Windows 2008 R2 has some nifty "green" features which is really a good step to narrow the gap of green characteristics between software and hardware.

You probably have heard about processors with “multicores” where a single physical processor internally has dual or quad cores presented to the OS as multiple “logical” processors. In a normal scenario once the OS is installed, all the cores are active and  start consuming power which could be a huge waste of resources if the application doesn’t need that much computing power. So, wouldn’t it be nice if we have a way to control this behavior somehow by making the cores “active” or “inactive”. The upcoming release of Windows Server 2008 R2 gives you just that capability and some additional ones. The following OS features improve reduce power consumption:

• Reduced multicore processor power consumption
• Reduced processor power consumption by adjusting processor speed
• Reduced storage power consumption

Reduced multicore processor power consumption

This feature itself is called as “Core Parking” and allows Windows Server 2008 R2 to consolidate processing onto the fewest number of possible processor core and suspend inactive processor cores, as show in the figure below.

If additional processing power is required, the “Core Parking” feature activates inactive processor cores “automatically” to handle the increased processing requirements. Needless to say, a new feature with “automation” to turn ON and OFF the heart of the computer needs to be watched out as it may indirectly affect the application response and performance if not activated on time. So, I’m not so sure what to say here as I haven’t witnessed the feature yet. Only MS can shed some light whether we can close our eyes and trust them that it really “works” :-). Anyway, I would try to get this clarified by MS folks with some good explanation to back the feature. So, watch out this space for more updates.

Reduced processor power consumption by adjusting processor speed

The second one on the list is the feature with an ability to adjust the ACPI “P-states” of processors and architecture. Windows Server 2008 R2 can adjust the “P-states” of individual processors and provide very fine control over power consumption as shown in the figure below:

One may ask, why would I really need to mess-up with the p-states on the processor cores to have them run on two different frequencies? Well, if you are really looking at ways to reduce your power consumption and looking to calculate an ROI out of it, then you got to do it. MS has given you some options to poke around with, and you need to go and figure to make the best use of it for your requirements.

Reduced storage power consumption

Have we ever thought about buying “diskless” servers yet? may be some folks did, but majority of us still buy servers with local storage. Diskless computing reminds me of those Novell days where all the nodes used to boot from a central server and things used to work well. All of sudden industry took a turn and we moved to decentralized computing, killing “centralized” approach completely. Now, after decades, we are talking about it again, sort of having “old wine in a new bottle”. And that is precisely the third option - “Reduced Storage Power Consumption”. Today many medium to large businesses have some kind of SAN storage in place, but they still buy servers with local storage. Why not we stop buying servers with local hard drives in it and make use of SAN instead to boot the OS? Booting the OS from SAN approach would give you a substantial amount of savings on power consumption. So, MS is asking customers to make use of Windows Server 2008 diskless boot from SAN feature to reduce the carbon footprint. 

Now, the million dollar question is, “How do I make use and set options 1 or 2 in my environment?”

Answer: “Use Active Directory Group Policy Settings”

Update:

New Hyper-V VMs will also consume less power by virtue of the new Core Parking Feature.

I recently did an implementation where the customer wanted to have a solution where they can have redundant print servers serving all the print queues and migrate all of them without any outage. Among couple of different options - MSCS, NLB, DFS etc, we went with NLB.

I'm going to give you the complete details on how we did it. Though this works seamlessly and customer is happy, it is not "supported" my MSFT. So, decide and use at you own risk.

1. Configure NLB on the 2 servers using the "Network Load Balancing Manager" (part of Admin Pack) use a dedicated NIC on each server and use unicast. Some CISCO routers do not pass ip address with multicast MAC addresses

2. Set NLB Port Rules to listen on port 135 (TCP/UDP) and ports 1024-65535 (TCP/UDP)

3. Configure the print queues identically on each server including Printer Name, Share Name, Driver etc. You can use printmig utility (download here). You can setup all your queues on one server and migrate them over using the tool to the second server very easitly.

4. Make the computer policy change on both servers. On the Local Computer Policy set "Computer Configuration > Administrative Templates > Printers > Allow Print Spooler to accept client connections" to Enabled and restart the Print Spooler service.

5. Manually create a DNS A record pointing to the IP of the NLB Cluster.

Now comes the tricky part - Obviously, those who need a new mapping would go with \\NLBClusterName\PrinterShareName, very simple and easy right?, but what about those users who are still mapped to the printers using old name? Alright, here's the trick - First you add a DNS A record for the name of each of the old print servers which points to the new cluster IP. Be sure to remove the old DNS entries or rename them to avoid duplicate name and un-planned outage (needless to say that a proper change management is required.)

7. Add an alias entry for each old server name you want the new server to be identified with on the new load balanced servers. The idea here is, if anyone uses old server name to map their printer, they'll automatically be re-directed to the new one.

Navigate to registry hive, HKEY_Local_Machine\System\CurrentControlSet\Services\LanmanServer\Parameters

Add Value: OptionalNames REG_SZ String: "Alias"

If you make it a type REG_MULTI_SZ, you can add multiple aliases.

If do not like step 7 and feel that you shouldn't be dealing with old print server names then use login scripts to re-map your users to the new print server or deploy a software package using a software deployment tool (SMS, Altiris etc) to re-map them.

Have Fun!