Tag Archives: automation

Quicky Review: GPO/GPP vs. DSC


If you’re not in a DevOps based shop, or living under a rock, you may not know that Microsoft has been working on a solution that by all accounts sounds like its poised to usurp GPO / GPP.  The solution I’m talking about is Desired State Configuration, or DSC. According to all the marketing hype, DSC is the next best thing for IT since virtualization.  If the vision comes to fruition, GPO and GPP will be a legacy solution.  Enterprise mobility management will be used for desktops and DSC will be used for servers.  Given that I currently manage 700 VM’s and about an equal number of desktops, I figured why not take it for a test drive. So I stood up a simplistic environment, and played around with it for a full week and my conclusion is this.

I can totally see why DSC is awesome for non-domain joined systems, but its absolutely not a good replacement in todays iteration for domain joined systems. Does that mean you should shun it since all your systems are domain joined?  That depends on the size of your environment and how much you care about consistency and automation.  Below are all my unorganized thoughts on the subject.

The points:

DSC can do everything GPO can do, but the reverse is not true. At first that sounds like DSC is clearly a winner, but I say no.  The reality is, GPO does what it was meant to do, and it does it well.  To reproduce what you’ve already done in GPO while certainly doable, has the potential of making your life hell.  Here are a few fun facts about DSC.

  1. The DSC “agent” runs as local system. This means it only has local computer rights, and nothing else.
  2. Every server that you want to manage with DSC, needs its own unique config file built. That means if you have 700 servers like me, and you want to manage them with DSC, they each are going to have a unique config file.  Don’t get me wrong, you can create a standard config, and duplicated it “x” times, but none the less, its not like GPO where you just drop the computer in an OU and walk away.  That being said, and to be fair, there’s no reason you couldn’t automate DSC config build process to do just that.
    1. DSC has no concept of “inheritance / merging” like you’re used to with GPO. Each config must be built to encompass all of those things that GPO would normally handle in a very easy way.  DSC does have config merges in the sense that you can have a partial config for say your OS team, your SQL team and maybe some other team.  So they can “merge” configs, and work on them independently (awesome).  However, if the DBA config and the OS config, conflict, errors are thrown, and someone has to figure it out.  Maybe not a bad thing at all, but none the less, it’s a different mindset, and there is certainly potential for conflicts to occur.
  3. A DSC configuration needs to store user credentials for a lot of different operations. It stores these credentials in a config file that hosted both on a pull server (SMB share / HTTPs site) and on the local host.  What this means is you need a certificate to encrypt the config file and then of course for the agent to decrypt the config file.  You thought managing certificates was a pain for a few exchange servers and some web sites?  Ha! now every server and the the build server need certs.  In the most ideal scenario, you’re using some sort of PKI infrastructure.  This is just the start of the complexity.
    1. You of course need to deploy said certificate to the DSC system before the DSC config file can be applied. In case you can’t figure it out by now, this is a boot strap solution you have to implement on your own if you don’t use GPO.  You could use the same certificate and bake it into an image.  That certainly makes your life easier, but its also going to make your life that much harder when it comes to replacing those certs on 700 systems.  Not to mention, a paranoid security nut would argue how terrible that potentially is.
  4. The DSC agent of course need to be configured before it knows what to do. You can “push” configurations, which does mitigate some of these issues, but the preferred method is “pull”.  So that means you need to find a way (boot strap again) to configure your DSC agent so that it knows where to pull its config from, and what certificate thumbprint to use.

Based on the above point, you probably think DSC is a mess, and to some degree it is. However, a few other thoughts.

  1. It’s a new solution, so it still needs time to mature. GPO has been in existence since 2000, and DSC, I’m going to guess, since maybe 2012.  GPO is mature, and DSC is the new kid.
  2. Remember when I wrote that DSC can do everything that GPO can do, but not the reverse? Well, lets dig into that.  Let’s just say you still manage Exchange on premises, or more likely, you manage some IIS / SQL systems.  DSC has the potential to make setting those up and administering them, significantly easier.  DSC can manage not only the simple stuff that GPO does, but also way beyond that.  For example, here are just a few things.
    1. For exchange:
      1. DSC could INSTALL exchange for you
      2. Configure all your connectors, including not only creating them, but defining all the “allowed to relay” and what not.
      3. Configure all your web settings (think removing the default domain\username).
      4. Install and configure your exchange certificate in IIS
      5. Configure all your DAG relationships
      6. Setup your disks and folders
    2. For SQL
      1. DSC could INSTALL sql for you.
      2. Configure your max member min memory
      3. Configure your TempDB requirements
      4. Setup all your SQL jobs and other default DB’s
    3. Pick another MS app, and there’s probably a series of DSC resources for it…
    4. DSC let’s you know when things are compliant, and it can automatically attempt to remediate them. It can even handle things like auto reboots if you want it to.  GPO can’t do this.  To the above point, what I like about DSC, is I’ll know if someone went in to my receive connector and added an unauthorized IP, and even better, DSC will whack it and set it back to what it should be.
    5. Part of me thinks that while DSC is cool, I wish Microsoft would just extend GPO to encompass the things that DSC does that GPO doesn’t. I know its because the goal is to start with non-domain joined systems, but none the less, GPO works well and honestly, I think most people would rather use GPO over DSC if both were equally capable.


Should you use DSC for domain joined systems?  I think so, or at least I think it would be a great way to learn DSC.  I currently look at DSC as being a great addition to GPO, not a replacement.  My goal is going to be to use GPO to manage the DSC dependencies (like the certificates as one example) and then use DSC for specific systems where I need consistency, like our exchange, SQL and web servers.  At this stage, unless you have a huge non-domain joined infrastructure, and you NEED to keep it that way, I wouldn’t use DSC to replace GPO.


Problem Solving: CommVault tape usage


I hate dealing with tapes, pretty much every aspect of them.  The tracking of them is a PITA, having to physically manage them is a PITA, dealing with tape library issues is a PITA, dealing with tape encryption is a PITA, running out of tapes is a PITA, dealing with legal hold for tapes is a PITA, and I could keep going on with the many ways that tape just sucks.  What makes matters worse is when you have to deal with MORE tapes.

Now that you know tapes are one of my personal seven levels of hell in IT, you’ll know why I put a bit of time into this solution.  Anything I can do to reduce the number of tapes getting exported every day, ultimately leads to some reduction in the PITA scale of tapes.

The issue:

To provide a better understanding of the issue at hand, for years I’ve been seeing way too many tapes being used by CV.  We’d kick out tapes that had 5% or 10% consumption, and the number of tapes with that level of consumption varied based on what phase of our backup strategy we were in, and what day of the week it was.  It could be anything as small as 4 partially filled tapes, to times where we had 10+ tapes that weren’t filled all the way up.  If the consumed data should fit on 16 tapes, and we’re kicking out 26 tapes, that’s a problem IMO.  I’m sure many of you out there have contended with this in CV specifically, and I’d bet those of you using other vendors products have run into this too.  I’m going to first explain why the problem is occurring, and then I’ll go over how I’ve reduced most of the waste.

The Why?

In CV, we have storage policies, and short of going into an explanation of what they are for others not familiar with CV, just think of it as an island of backup data.  That island of data doesn’t co-mingle with other islands of data on disk, and tape is no exclusion.  What that means is when you backup data to a storage policy and want to copy it to tape, that data getting copied to tape will automatically reserve the entire tape being used.  In turn, each storage policy then reserves its own unique tapes so that data does not co-mingle together.  This means for every storage policy you have, you’re guaranteed at least one unique tape per storage policy at a minimum.  Now, each storage policy can have a number of streams configured.  To keep things simple, let’s just ignore multiplexing for now.  When a storage policy has a stream limit of 1, that means only 1 tape drive will be used, when it has a stream policy of 4, that means 4 tape drives will be used.  Now, as you copy data to tape, you normally have more than 1 streams worth of data, you probably have at least one for each client in your environment (and likely much more than that).  This is a good thing, having more streams means we can run data copy operations in parallel.  In the case of the 4 streams example, that means we can use 4 tape drives in parallel to copy data for the example storage policy.  What this also means is depending on circumstances, we could end up with 4 tapes not being filled all the way as well.  Streams are optimized for performance, NOT for improving tape utilization.  Now, imagine you have more than one storage policy, let’s just say 4 storage polices, each being their own island, and each with a stream limit of 2.  That means you could end up with up to 8 tapes not being fully utilized.  I’m also ignoring for now that in CV, you can separate incremental and fulls to different storage policies which exacerbates the problem further (taking one island and making it two).

In our case, we have 4 storage policies and we had gone through a process of merging our Fulls and Incs into a single storage policy to consolidate tapes already.  We have a total of 6 tape drives, which means if we just configured the storage policies to fight over the tape drives @6 streams each, we could end up in theory with 24 partially filled tapes.  We’re smarter than that of course, so that wasn’t out problem.  Our problem was finding the right balance between how many streams a storage policy needed to copy all its data in our window, and not making it so high that we ended up wasting tape.  Pre-solution, we almost always had 4 – 6 tapes that were wasted, as in 100GB on a 2000GB tape.  It was annoying and wasteful.

Solution, problems again, improved solution:

There are two main components to the solution.

  • Scripting storage policy stream modification via task scheduler (MVP JAMS in our case).
  • CommVault introducing Global Tape Policies in v11
    • This allows tapes to be shared, no longer residing on an island as mentioned above. So storage policy 1, 2, 3 and 4 can all share the same tape.  Way more efficient.

In our case, when we saw the global tape policy, it was like a halo of light and angels singing, going off in our head.  This was it, our problems were FINALLY solved.  After going through the very tedious task of migrating to this solution, we found that we were still using 4 – 6 tapes a day more than we needed.  The problem was not that data was not co-mingling, it was.  No, the problem was that we set the global tape policy to 6 streams, and every day, it was using 6 tape drives for backups.   At first we tried to solve the problem by limiting the aux copy streams via a scheduled task in CV (start the job with 1 stream only as an example) but we had 4 storage polices, so that only reduced the tape usage to 4.  The problem again was that each storage police was scheduled and run in parallel.  So while we restricted any one storage policy, ultimately we were still letting more tape drives being used than needed and in turn more tapes than was needed.  We had set 6 streams, because we wanted to make sure that our FULL jobs had enough tape drives to complete over the weekend.

At this stage, I came to the conclusion that we needed a way to dynamically control the streams for the global tape policy so that during the week days it was restricted to 1 tape drive (all we needed) and on the weekend, we could start out with 6 and slowly ramp back down to 1, and hopefully more fully fill our tapes.  With a bit of research and some discussions with CV, I found out that they have a CLI option for controlling storage policy streams (found https://documentation.commvault.com/commvault/v10/article?p=features/storage_policies/storage_policy_xml_edit.htm).  Using my trusty scheduling tool, I setup a basic system where on Sunday @4PM we would set the streams to “1”, and then on Friday @4PM we would raise them to “6” and Saturday @7am we would drop them to “2”.  This basically solved our problem, and I’m happy to say that on week days, tapes are filled as much as is possible (1 – 2 tapes depending on which client ran a full), and on the weekend, 2 – 4 tapes are still being used.  I’m still tuning the whole thing, for the fulls (it’s a balance of utilization and performance), but its better than its ever been.  Its also worth noting, we went back and modified our aux copy schedules and told them to use all available streams since we now choke point it at the global tape policy.  This allows any storage policy to go as fast as possible (although potentially blocking other ones).

It’s a hack no doubt.  IMO, CV should develop this concept in their storage policies.  Basically creating a schedule window to dynamically control the queue depth.  For now, this is working well.