Hyper-V UNMAP Does Work With SAN Snapshots And Checkpoints But Not Always As You First Expect


Recently I was asked to take a look at why UNMAP was not working predictably  in a Windows Server 2012 R2 Hyper-V environment. No, this is not a horror story about bugs or bad storage solutions. Fortunately, once the horror option was of the table I had a pretty good idea what might be the cause.

San snapshots are in play

As it turned out everything was indeed working just fine. The unexpected behavior that made it seem that UNMAP wasn’t working well or at least at moments they didn’t expected it was caused by the SAN snapshots. Once you know how this works you’ll find that UNMAP does indeed work predictably.

Snapshots on SANs are used for automatic data tiering, data protection and various other use cases. As long as those snapshots live, and as such the data in them, UNMAP/Trim will not free up space on the SAN with thinly provisioned LUNs. This is logical, as the data is still stored on the SAN for those snapshots, hard deleting it form the VM or host has no impact on the storage the SAN uses until those snapshots are deleted or expire. Only what happens in the active portion is directly impacted.

An example

  • Take a VM with a dynamically expanding VHDX that’s empty and mapped to drive letter D. Note the file size of the VHDX and the space consumed on the thinly provisioned SAN LUN where it resides.
  • Create 30GB of data in that dynamically expanding  virtual hard disk of the virtual machine
  • Create a SAN snapshot
  • Shift + Delete that 30GB of data from the dynamically expanding virtual hard disk in the virtual machine. Watch the dynamically expanding VHDX  grow in size, just like the space consumed on the SAN
  • Run Optimize-Volume D –retrim to force UNMAP and watch the space consumed of the Size of the LUN on the SAN: it remains +/- the same.
  • Shut down the VM and look at the size of the dynamic VHDX file. It shrinks to the size before you copied the data into it.
  • Boot the VM again and copy 30GB of data to the dynamically expanding VHDX in the VM again.
  • See the size of the VHDX grow and notice that the space consumed on the SAN for that LUN goes up as well.
  • Shift + Delete that 30GB of data from the dynamically expanding  virtual hard disk in the virtual machine
  • Run Optimize-Volume D –retrim to force UNMAP and watch the space consumed of the Size of the LUN on the SAN: It drops, as the data you delete is in the active part of your LUN (the second 30GB you copied), but it will not drop any more than this as the data kept safe in the frozen snapshot of the LUN is remains there (the first 30GB you copied)
  • When you expire/delete that snapshot on the SAN  we’ll see the size on the thinly provisioned SAN LUN  drop to the initial size of this exercise.

I hope this example gave you some insights into the behavior

Conclusion

So people who have snapshot based automatic data tiering, data protection etc. active in their Hyper-V environment and don’t see any results at all should check those snapshot schedules & live times. When you take them into consideration you’ll see that UNMAP does work predictably, all be it in a “delayed” fashion Smile.

The same goes for Hyper-V checkpoints (formerly known as snapshots). When you create a checkpoint the VHDX is kept and you are writing to a avhdx (differencing disk) meaning that any UNMAP activity will only reflect on data in the active avhdx file and not in the “frozen” parent file.

Mind the UNMAP Impact On Performance In Certain Scenarios


The Problem

Recently we’ve been trouble shooting some weird SQL Server to file backup issues. They started failing on the clock at 06:00 AM. We checked the NICs, the switches, the drivers, the LUNs, HBAs, … but it was all well. We considered over stressed buffers as the root cause or spanning tree issues but the clock steadiness of it all was weird. We tried playing with some time out parameters but with little to no avail. Until the moment it hit me, the file deletions that clean up the old backups!We had UNMAP enabled recently on the SAN.

Take a look at the screenshot below an note the deletion times underlined in red. That’s with UNMAP enabled. Above is with UNMAP disabled. The Backup jobs failed waiting for the deletion process.

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This is a no issues if your backup target is running something prior to Windows Server 2012. if not, UNMAP is disabled by default. I know about the potential performance impact of UNMAP when deleting or more larger files due to the space reclamation kicking in. This is described here Plan and Deploy Thin Provisioning under the heading “Consider space reclamation and potential performance impact”. But as I’m quite used to talking about many, many terabytes of data I kind of forget to think of 500 to 600GB of files as “big” Embarrassed smile. But it seemed to a suspect so we tested certain scenarios and bingo!

Solutions

  1. Disable the file-delete notification that triggers real-time space reclamation. Find the following value HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\FileSystem\DisableDeleteNotification and set it to 1.

    Note that: This setting is host wide, so for all LUNs. Perhaps that server has many other roles or needs to server that could benefit from UNMAP. If not this is not an issue.  It is however very efficient in avoiding issues. You can still use the Defragment and Optimize Drives tool to perform space reclamation on-demand or on a scheduled basis.

  2. Create LUNs that will have high deltas in a short time frame as fully provisioned LUNs (aka thick LUNs). As you do this per LUN and not on the host it allows for more fine grained actions than disabling UNMAP.  It makes no sense to have UNMAP do it’s work to reclaim the free space that deleting data created when you’ll just be filling up that space again in the next 24 hours in an endless cycle. Backup targets are a perfect example of this. This avoid the entire UNMAP cycle and you won’t mind as it doesn’t make much sense and fixes you issue. The drawback is you can’t do this for an existing volumes. So it has some overhead & downtime involved depending on the SAN solution you use. It also means that you have to convince you storage admins to give you fully provisioned LUNs, which might or might not be easy depending on how things are organized.

Conclusion

UNMAP has many benefits both in the physical and virtual layer. As with all technologies you have to understand its capabilities, requirements, benefits and draw backs. Without this you might run into trouble.

Future Proofing Storage Acquisitions Without A Crystal Ball


Dealing with an unknown future without a crystal ball

I’ve said it before and I’ll say it again. Storage Spaces in Windows Server 2012 (R2) is are the first steps of MSFT to really make a difference (or put a dent into) in the storage world. See TechEd 2013 Revelations for Storage Vendors as the Future of Storage lies With Windows 2012 R2 (that was a nice blog by the way to find out what resellers & vendors have no sense of humor & perspective). It’s not just Microsoft who’s doing so. There are many interesting initiatives at smaller companies to to the same. The question is not if these offerings can match the features sets, capabilities and scenario’s of the established storage vendors offerings. The real question is if the established vendors offer enough value for money to maintain themselves in a good enough is good enough world, which in itself is a moving target due to the speed at which technology & business needs evolve. The balance of cost versus value becomes critical for selecting storage. You need it now and you know you’ll run it for 3 to 5 years. Perhaps longer, which is fine if it serves your needs, but you just don’t know. Due to speed of change you can’t invest in a solution that will last you for the long term. You need a good fit now at reasonable cost with some headway for scale up / scale out. The ROI/TCO has to be good within 6 months or a year. If possible get a modular solution. One where you can replace the parts that are the bottle neck without having to to a fork lift upgrade. That allows for smaller, incremental, affordable improvements until you have either morphed into a new system all together over a period of time or have gotten out of the current solution what’s possible and the time has arrived to replace it. Never would I  invest in an expensive, long term, fork lift, ultra scalable solution. Why not. To expensive and as such to high risk. The risk is due to the fact I don’t have one of these:

http://trustbite.co.nz/wp-content/uploads/2010/01/Crystal-Ball.jpg

So storage vendors need to perform a delicate balancing act. It’s about price, value, technology evolution, rapid adoption, diversification, integration, assimilation & licensing models in a good enough is good enough world where the solution needs to deliver from day one.

I for one will be very interested if all storage vendors can deliver enough value to retain the mid market or if they’ll become top feeders only. The push to the cloud, the advancements in data replication & protection in the application and platform layer are shaking up the traditional storage world. Combine that with the fast pace at which SSD & Flash storage are evolving together with Windows Server 2012 that has morphed into a very capable storage platform and the landscape looks very volatile for the years to come. Think about  ever more solutions at the application (Exchange, SQL server) and platform layer (Hyper-V replica) with orchestration on premise and/or in the cloud and the pressure is really on.

So how do you choose a solution in this environment?

Whenever you are buying storage the following will happen. Vendors, resellers & sales people, are going to start pulling at you. Now, some are way better than others at this, some are even down right good at this whole process a proceed very intelligently.

Sometimes it involves FUD, doom & gloom combined with predictions of data loss & corruption by what seem to be prophets of disaster. Good thing is when you buy whatever they are selling that day, they can save you from that. The thing is this changes with the profit margin and kickbacks they are getting. Sometimes you can attribute this to the time limited value of technology, things evolve and todays best is not tomorrows best. But some of them are chasing the proverbial $ so hard they portray themselves as untrustworthy fools.

That’s why I’m not to fond of the real big $ projects. Too much politics & sales. Sure you can have people take care of but you are the only one there to look out for your own interests. To do that all you need to do is your own due diligence and be brave. Look, a lot of SAN resellers have never ever run a SAN, servers, Hyper-V clusters, virtualized SQL Server environments or VDI solutions in your real live production environments for a sustained period of time. You have. You are the one whose needs it’s all about as you will have to live and work with the solution for years to come.  We did this exercise and it was worth while. We got the best value for money looking out for our own interests.

Try this with a reseller or vendor. Ask them about how their hardware VSS providers & snapshot software deals with the intricacies of CSV 2.0 in a Hyper-V cluster. Ask them how it works and tell them you need to references to speak to who are running this in production. Also make sure you find your own references. You can, it’s a big world out there and it’s a fun exercise to watch their reactions Winking smile

As Aidan remarked in his blog on ODX–Not All SANs Are Created Equally

These comparisons reaffirm what you should probably know: don’t trust the whitepapers, brochures, or sales-speak from a manufacturer.  Evidently not all features are created equally.

You really have to do your own due diligence. Some companies can afford the time, expense & personnel to have the shortlisted vendors deliver a system for them to test. Costs & effort rise fast if you need to get a setup that’s comparable to the production environment. You need to device tests that mimic real life scenario’s in storage capacity, IOPS, read/write patterns and make sure you don’t have bottleneck outside of the storage system in the lab.

Even for those that can, this is a hard thing to do. Some vendors also offer labs at their Tech Centers or Solutions Centers where customers or potential customers can try out scenarios. No matter what options you have, you’ll realize that this takes a lot of effort. So what do I do? I always start early. You won’t have all the information, question & answers available with a few hours of browsing the internet & reading some brochures. You’ll also notice that’s there’s always something else to deal with or do, so give your self time, but don’t procrastinate. I did visit the Tech Centers & Solution Centers in Europe of short listed vendors. Next to that I did a lot of reading, asked questions and talked to a lot of people about their view and experiences with storage. Don’t just talk to the vendors or resellers. I talked a lot with people in my network, at conferences and in the community. I even tracked down owners of the shortlisted systems and asked to talk to them. All this was part of my litmus test of the offered storage solutions. While perfection is not of this world there is a significant difference between vendor’s claims and the reality in the field. Our goal was to find the best solution for our needs based on price/value and who’s capabilities & usability & support excellence materialized with the biggest possible majority of customers in the field.

Friendly Advice To Vendors

So while the entire marketing and sales process is important for a vendor I’d like to remind all of them of a simple fact. Delivering what you sell makes for very happy customers who’s simple stories of their experiences with the products will sell it by worth of mouth. Those people can afford to talk about the imperfections & some vNext wishes they have. That’s great as those might be important to you but you’ll be able to see if they are happy with their choice and they’ll tell you why.

Upgrading Your DELL Compellent Storage Center Firmware (Part 2)


This is Part 2 of this blog. You’ll find Part 1 over here.

In part 1 we prepared our Compellent SAN to be ready and install Storage Center 6.3.10 that has gone public.  As said, 6.3.10 brings interesting features like ODX and UNMAP to us Windows Server 2012 Hyper-V users. It also introduces some very nice improvements to synchronous replication and Live Volumes. But here we’ll just do the actual upgrade, the preparations & health check have been done in part 1 so we can get started here right away.

Log in to your Compellent system and navigate to the Storage Management menu. Click on “System”, select Update and finally click on “Install Update”.  It’s already there as we downloaded it in Part 1. Click on “Install Now” to kick it all off.

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Click on Install now to launch the upgrade.

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After initialization you can walk away for 10 minutes but you might want to keep an eye on things and the progress of the process.

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So go have a look at your storage center. Look at the Alert Monitor for example and notice that the “System is undergoing maintenance”.

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When the controller the VIP address of the SAN reboots it becomes unavailable. After a while you can login again to the other controller via the VIP, if you cant’ wait a few seconds just use the IP address of the active controller. That will do.

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When you log in again you’ll see the evidence of an ongoing SAN firmware upgrade. Nothing to panic about.image

This is also evident in Alert Monitor. CoPilot knows you’re doing the upgrade so no unexpected calls to make sure your system is OK will come in. They’re there every step of the way. The cool thing is that is the very first SAN we ever owned that we don’t need engineers on site or complex and expensive procedure to do all this. It’s all just part of an outstanding customer service Compellent & DELL deliver.image

You can also take a peak at your Enterprise manager software to see paths going down and so on. The artifacts of a sequential controller failovers during an upgrade. Mind you you’re not suffering downtime in most cases.image

Just be patient and keep an eye on the process. When you log in again after the firmware upgrade and your system is up and running again, you’ll be asked to rebalance the ports & IO load between the controllers on the system. You do, so click yes.image

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When done you’ll return to the Storage Center interface. Navigate to “Help”" and click on About Compellent Storage Center. image

You can see that both controllers are running 6.3.10.

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You’re rocking the new firmware. As you kept an eye on your hosts you should know these are good to go. Send of an e-mail to CoPilot support and they’ll run a complete health check on your system to make sure you’re good to go. Now it’s time to start leveraging the new capabilities you just got.

Upgrading Your DELL Compellent Storage Center Firmware (Part 1)


This is Part 1 of this blog. You’ll find Part 2 over here

Well the Compellent firmware 6.3.10 has gone public and it’s time to put it on our systems. 6.3 brings interesting features like ODX and UNMAP to us Windows Server 2012 Hyper-V users. It also introduces some very nice improvements to synchronous replication and Live Volumes. But’s those are matters for other blog posts. Here We’ll focus on the upgrade.

In part 1 we’ll look at how we prepare the Compellent to be ready to apply the upgrade. We make sure on our side we have no outstanding issues on the SAN. Then we made sure we upgraded Enterprise Manager and Replay Manager to the latest versions. At this time of writing that is EM 6.3.5.7 and RM 7.0.1.1. We could do this prior to the firmware upgrade because 6.2.2. is also supported by these versions. Once we established all was working well with this software we contacted CoPilot to check our systems (the check it’s health an applicability as well). When all is in order they’ll release the firmware to us. Then It’s time to run a check for update on the systems.

Log in to your Compellent system and navigate to the Storage Management menu. Click on “System”, select Update and finally click on “Check for Update”.
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The tool will check for updates.

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If no new firmware has been released to your systems you’ll see this.image

If new firmware has been released you see this in the update status.image

This also shows in the Storage Center GUI

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Downloading the update.

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The download takes a while. Once it’s done you’ll see that the update is ready to install. Note that this update is non service affecting in OUR case (green arrow). We won’t install it yet however. We’ll look at the details & validate the components. Due diligence pays off Winking smileimage

Click on details to get some more information about what’s in the update. image

You can see that our disk and enclosure firmware is up to date already from a previous update. The ones related to 6.3.10 are mandatory( required, not optional). When done, hit Return.

We now select “Validate Components” to make sure we’re good to go and won’t get any surprises. Trust but verify is one of our mantras.image

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So now we are ready to run the update.  We’ll leave that for Part 2.

Some ODX Fun With Windows Server 2012 R2 And A Dell Compellent SAN


I’m playing and examining some of the ODX capabilities of our SANs (Dell, Compellent) at the moment. It all seems pretty impressive in the demo’s. But how does that behave in real live on our gear? How impressive is ODX? Well pretty darn impressive actually. And as all great power it needs to be wielded carefully, with insight and thought.

Let’s create some fixed virtual disks. 10 * 50GB vhdx and 10* 475GB vhdx. We run a simple quick PowerShell script:

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You see this correctly, it’s 41.5088855 seconds. let’s round up to 42 seconds. That’s 20 fixed VHDX files. 10 of 50GB, 10 of 475GB in 42 seconds. That’s a total of 5.12TB of vhdx files.

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Compared to creating a single 5TB vhdx file this isn’t to shabby as that get done in 26 seconds!

You can only dream of the kind of scenario’s this kind of power enables. Woooot!!!

TechEd 2013 Revelations for Storage Vendors as the Future of Storage lies With Windows 2012 R2


Imagine you’re a storage vendor until a few years ago. Racking in the big money with profit margins unseen by any other hardware in the past decade and living it up in dreams along the Las Vegas Boulevard like there is no tomorrow. To describe your days only a continuous “WEEEEEEEEEEEEEE” will suffice.

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Trying to make it through the economic recession with less Ferraris has been tough enough. Then in August 2012 Windows Server 2012 RTMs and introduces Storage Spaces, SMB 3.0 and Hyper-V Replica. You dismiss those as toy solutions while the demos of a few 100.000 to > million IOPS on the cheap with a couple of Windows boxes and some alternative storage configurations pop up left and right. Not even a year later Windows Server 2012 R2 is unveiled and guess what? The picture below is what your future dreams as a storage vendor could start to look like more and more every day while an ice cold voice sends shivers down your spine.

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“And I looked, and behold a pale horse: and his name that sat on him was Death, and Hell followed with him.”

OK, the theatrics above got your attention I hope. If Microsoft keeps up this pace traditional OEM storage vendors will need to improve their value offerings. My advice to all OEMs is to embrace SMB3.0 & Storage Spaces. If you’re not going to help and deliver it to your customers, someone else will. Sure it might eat at the profit margins of some of your current offerings. But perhaps those are too expensive for what they need to deliver, but people buy them as there are no alternatives. Or perhaps they just don’t buy anything as the economics are out of whack. Well alternatives have arrived and more than that. This also paves the path for projects that were previously economically unfeasible. So that’s a whole new market to explore. Will the OEM vendors act & do what’s right? I hope so. They have the distribution & support channels already in place. It’s not a treat it’s an opportunity! Change is upon us.

What do we have in front of us today?

  • Read Cache? We got it, it’s called CSV Cache.
  • Write cache? We got it, shared SSDs in Storage spaces
  • Storage Tiering? We got it in Storage Spaces
  • Extremely great data protection even against bit rot and on the fly repairs of corrupt data without missing a beat. Let me introduce you to ReFS in combination with Storage Spaces now available for clustering & CSVs.
  • Affordable storage both in capacity and performance … again meet storage spaces.
  • UNMAP to the storage level. Storage Spaces has this already in Windows Server 2012
  • Controllers? Are there still SAN vendors not using SAS for storage connectivity between disk bays and controllers?
  • Host connectivity? RDMA baby. iWarp, RoCE, Infiniband. That PCI 3 slot better move on to 4 if it doesn’t want to melt under the IOPS …
  • Storage fabric? Hello 10Gbps (and better) at a fraction of the cost of ridiculously expensive Fiber Channel switches and at amazingly better performance.
  • Easy to provision and manage storage? SMB 3.0 shares.
  • Scale up & scale out? SMB 3.0 SOFS & the CSV network.
  • Protection against disk bay failure? Yes Storage Spaces has this & it’s not space inefficient either Smile. Heck some SAN vendors don’t even offer this.
  • Delegation capabilities of storage administration? Check!
  • Easy in guest clustering? Yes via SMB3.0 but now also shared VHDX! That’s a biggie people!
  • Hyper-V Replication = free, cheap, effective and easy
  • Total VM mobility in the data center so SAN based solutions become less important. We’ve broken out of the storage silo’s

You can’t seriously mean the “Windoze Server” can replace a custom designed SAN?

Let’s say that it’s true and it isn’t as optimized as a dedicated storage appliance. So what, add another 10 commodity SSD units at the cost of one OEM SSD and make your storage fly. Windows Server 2012 can handle the IOPS, the CPU cycles, memory demands in both capacity and speed together with a network performance that scales beyond what most people needs. I’ve talked about this before in Some Thoughts Buying State Of The Art Storage Solutions Anno 2012. The hardware is a commodity today. What if Windows can and does the software part? That will wake a storage vendor up in the morning!

Whilst not perfect yet, all Microsoft has to do is develop Hyper-V replica further. Together with developing snapshotting & replication capabilities in Storage Spaces this would make for a very cost effective and complete solution for backups & disaster recoveries. Cheaper & cheaper 10Gbps makes this feasible.  SAN vendors today have another bonus left, ODX. How long will that last? ASIC you say. Cool gear but at what cost when parallelism & x64 8 core CPUs are the standard and very cheap. My bet is that Microsoft will not stop here but come back to throw some dirt on a part of classic storage world’s coffin in vNext. Listen, I know about the fancy replication mechanisms but in a virtualized data center the mobility of VM over the network is a fact. 10Gbps, 40Gbps, RDMA & Multichannel in SMB 3.0 puts this in our hands. Next to that the application level replication is gaining more and more traction and many apps are providing high availability in a “shared nothing“ fashion (SQL/Exchange with their database availability groups, Hyper-V, R-DFS, …). The need for the storage to provide replication for many scenarios is diminishing. Alternatives are here. Less visible than Microsoft but there are others who know there are better economies to storage http://blog.backblaze.com/2011/07/20/petabytes-on-a-budget-v2-0revealing-more-secrets/ & http://blog.backblaze.com/2011/07/20/petabytes-on-a-budget-v2-0revealing-more-secrets/.

The days when storage vendors offered 85% discounts on hopelessly overpriced storage and still make a killing and a Las Vegas trip are ending. Partners and resellers who just grab 8% of that (and hence benefits from overselling as much a possible) will learn just like with servers and switches they can’t keep milking that cash cow forever. They need to add true and tangible value. I’ve said it before to many VARs have left out the VA for too long now. Hint: the more they state they are not box movers the bigger the risk that they are. True advisors are discussing solutions & designs. We need that money to invest in our dynamic “cloud” like data centers, where the ROI is better. Trust me no one will starve to death because of this, we’ll all still make a living. SANs are not dead. But their role & position is changing. The storage market is in flux right now and I’m very interested in what will happen over the next years.

Am I a consultant trying to sell Windows Server 2012 R2 & System Center? No, I’m a customer. The kind you can’t sell to that easily. It’s my money & livelihood on the line and I demand Windows Server 2012 (R2) solutions to get me the best bang for the buck. Will you deliver them and make money by adding value or do you want to stay in the denial phase? Ladies & Gentleman storage vendors, this is your wake-up call. If you really want to know for whom the bell is tolling, it tolls for thee. There will be a reckoning and either you’ll embrace these new technologies to serve your customers or they’ll get their needs served elsewhere. Banking on customers to be and remain clueless is risky. The interest in Storage Spaces is out there and it’s growing fast. I know several people actively working on solutions & projects.

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You like what you see? Sure IOPS are not the end game and a bit of a “simplistic” way to look at storage performance but that goes for all marketing spin from all vendors.

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Can anyone ruin this party? Yes Microsoft themselves perhaps, if they focus too much on delivering this technology only to the hosting and cloud providers. If on the other hand they make sure there are feasible, realistic and easy channels to get it into the hands of “on premise” customers all over the globe, it will work. Established OEMs could be that channel but by the looks of it they’re in denial and might cling to the past hoping thing won’t change. That would be a big mistake as embracing this trend will open up new opportunities, not just threaten existing models. The Asia Pacific is just one region that is full of eager businesses with no vested interests in keeping the status quo. Perhaps this is something to consider? And for the record I do buy and use SANs (high-end, mid-market, or simple shared storage). Why? It depends on the needs & the budget. Storage Spaces can help balance those even better.

Is this too risky? No, start small and gain experience with it. It won’t break the bank but might deliver great benefits. And if not .. there are a lot of storage options out there, don’t worry. So go on Winking smile