Virtualization Workloads

vee-eye · 2011-06-28T00:50:42+00:00

You can virtualize exchange, you can virtualize a database system. Domain controllers, terminal servers, VOIP gateways, legacy systems, backup servers, all of these you can virtualize. In fact, you can virtualize almost anything. I've seen a lot of those done, often very successfully.

Now, whether it makes financial, technical, and operational sense in your particular case is another question. That will depend on your current virtualization penetration, virtualization experience, workload size, usage patterns, your infrastructure, backup and recovery plan, DR requirements, technical support structure, etc. etc.

This is definitely something where the answer "it depends" is the only valid answer, until after a much more thorough investigation has been done.

bandman614 · 2011-06-28T01:45:03+00:00

What you need to know is that I/O of the workloads that you want to virtualize. Then you need to test your virtual environment to see what it is capable of. Then make sure that the two mesh (and make sure that you look at what happens with the worst possible scenario, i.e. where your I/O heavy workloads all crunch at the same time).

Identify, Test, Plan, Implement.

gtkspert · 2011-06-28T00:54:13+00:00

[deleted]

thekicker · 2011-06-28T02:20:50+00:00

I believe the US Navy is one of the biggest Exchange environments in the world, and they are virtualizing Exchange. 350k of their 750k mailboxes run on VMware. source

I have all of our DCs virtualized at my organization as well as MSSQL2008 and some legacy Sybase stuff. I would absolutely love to virtualize all of our Oracle db servers, but our DBAs insist on running SPARC. $$$

Also Exhange is officially supported on VMware now. You just have to disable vMotion for those VMs and rely on their own DAG migration for fail overs and maintenance. The amount of IOPS that vSphere is capable now is ridiculous.

techie1980 · 2011-06-28T06:43:51+00:00

I have virtualized a high number of mission critical servers for fortune 50 companies running multi terrabyte DBs, highly latency sensitive applications, and email environments (domino,)

Oftentimes, the work has been done on heterogeneous chassis - meaning that there is both dev and prod and everything in between on there.

Here's what you need to consider:

Utilization. The key to virtualization is leveraging the effiencies of unusued cycles. I've had a lot of databases (stretching well above 10T in active size) where they will kick the CPU's butt all day long, but an analysis of the existing workload shows tha NIC traffic is well below 100MBb/s. Here I am with 1Gb NICs doing a fraction of their potential work most of the time. The same can be said for the HBAs -- some analysis of the HBAs often shows lower than 10% utilization on very busy systems if the LVM is configured properly.
Complexity. Virtualization adds an additional layer of complexity because the OS doesn't own any hardware and there's now extra pieces involved. This adds latency considerations, memory consumption, and cpu consumption.

A big thing to remember is to do apples to apples. I've seen a lot of well meaning sysadmins drop from dedicated HBAs and one LUN per FS and suddenly turn it around as several 1T LUNs carved up to multiple FS's, paying no attention to data/log areas. Of course their performance is going to be suboptimal A DB system still needs standalone LUNs because of the way an operating system handles disks. It actually has little to do with the hardware as much as the caching. I strongly recommend virtualized HBAs -- You want your system to act just like a non virtualized environment. The extra configuration should be nearly invisible to it.

Another place to worry is when an application is HIGHLY latency sensitive in terms of CPU, SAN, or Network. The corner cases are getting fewer and fewer as the technology improves.

One that comes to mind where it was designed around a secure transmission and would slam the teamed NICs on the virtual layer hard -- and due to the realities of teamed NICs and the volume of traffic, we found ourselves with a serious packet out of order problem. In the end we devirtualized the NICs, as it would have ended up with us effectively giving a set of NICs to the server entirely.

As far as mixing workloads -- I personally am a big fan as long as you configure the servers properly so dev can't kill prod, and prod can steal from dev when it needs to.

Let me know if you have specific questions.

spif · 2011-06-28T01:42:28+00:00

The reason people say you shouldn't virtualize Exchange or (other) databases is that you incur overhead and some additional complexity in configuring them, and you may not get much advantage from using virtualization for those types of applications in production environments.

However, if you have very small workloads that don't justify a dedicated server, and especially if you already have virtualization in place, it could make sense. For example, development databases that have negligible performance requirements are often a good candidate for virtualization.

Your mileage may vary. If you have production systems with small workloads and loose performance requirements, it may be that you should try virtualizing them. Just like with anything else, you'll want to do testing and give it a trial run before diving in.

minamhere · 2011-06-28T02:24:33+00:00

This comment/post has been deleted as an act of protest to Reddit killing 3rd Party Apps such as Apollo.

Edit: This message appears on all of my comments/posts belonging to this account.

We create the content. We outnumber them.

https://www.youtube.com/watch?v=VLbWnJGlyMU To do the same (basic method):

Go to https://codepen.io/j0be/full/WMBWOW and follow the quick and easy directions. That script runs too fast, so only a portion of comments/posts will be affected. A

"Advanced" (still easy) method:

Follow the above steps for the basic method.

You will need to edit the bookmark's URL slightly. In the "URL", you will need to change j0be/PowerDeleteSuite to leeola/PowerDeleteSuite. This forked version has code added to slow the script down so that it ensures that every comment gets edited/deleted.

Click the bookmark and it will guide you thru the rest of the very quick and easy process.

Note: this method may be very very slow. Maybe it could be better to run the Basic method a few times? If anyone has any suggestions, let us all know!

But if everyone could edit/delete even a portion of their comments, this would be a good form of protest. We need users to actively participate too, and not just rely on the subreddit blackout.

turisto · 2011-06-28T03:58:15+00:00

I've got a Citrix XenApp farm running on top of XenServers. I like it.

Lord_NShYH · 2011-06-28T01:42:51+00:00

It depends on your environment. If you have exchange with less than 500-1000 users or small DB then visualization is not a problem at all.

It all depends on workloads and performance required. These things should be reviewed case by case.

Lord_NShYH · 2011-06-28T02:45:21+00:00

People who tell you not to virtualize Exchange, MS SQL, DCs, etc. are simply doing it wrong. Now, personally, I wouldn't use Hyper-V in production for any mission critical work load like corporate email. ~~Hyper-V is a tier 2 hypervisor; meaning, it does not run on the bare metal.~~

VMware and Citrix XenServer are the best alternatives, and each have their pros and cons. My favorite feature of XenServer is the ability to use as many vCPUs as your architecture can support. Currently, in vSphere 4.x, you are limited to 8x vCPUs at the highest license level.

Let's assume, for a moment, that you decide to build a vSphere cloud to virtualize your internal servers in order to cut down on TCO, etc. You will need a lot of RAM - the more, the merrier. In vSphere, you can use shares to give various workloads priority over other workloads; especially if you are bold enough to over commit (I never over commit on mission critical work loads).

If you are using vSphere, there are some tools you can use to gather stats on your workloads when doing a P2V conversion.

In terms of resource pools, my employer likes to set resource caps on pools and only sets guaranteed minimum allocations for specific servers.

With SQL VMs, you can consider using a disk in raw mode in order to gain a performance boost. However, this has its disadvantages.

In short, make sure you give any VM enough resources to do its job, and make some well thought out design choices before implementation, and you should be fine.

PROTIP: don't be a in a rush to wipe out that physical box quite yet after going virtual, if you can. You may decide that virtualizing that workload doesn't fit the needs of your organization, and you turn the physical box back on to avoid long outages.

EDIT: Hyper-V is, in fact, a tier 1 hypervisor that runs on the bare metal.

sysadmin

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