Category Archives: DELL

Dell Storage Replay Manager 7.6.0.47 for Compellent 6.5

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Recently as a DELL Compellent customer version 7.6.0.47 became available to us. I download it and found some welcome new capabilities in the release notes.

  • Support for vSphere 6
  • 2024 bit public key support for SSL/TLS
  • The ability to retry failed jobs (Microsoft Extensions Only)
  • The ability to modify a backup set (Microsoft Extensions Only)

The ability to retry failed jobs is handy. There might be a conflicting backup running via a 3rd party tool leveraging the hardware VSS provider. So the ability to retry can mitigate this. As we do multiple replays per day and have them scheduled recurrently we already mitigated the negative effects of this, but this only gibes us more options to deal with such situations. It’s good.

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The ability to modify a backup set is one I love. It was just so annoying not to be able to do this before. A change in the environment meant having to create a new backup set. That also meant keeping around the old job for as long as you wanted to retain the replays associated with that job. Not the most optimal way of handling change I’d say, so this made me happy when I saw it.

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Now I’d like DELL to invest a bit more in make restore of volume based replays of virtual machines easier. I actually like the volume based ones with Hyper-V as it’s one snapshot per CSV for all VMs and it doesn’t require all the VMs to reside on the host where we originally defined the backup set. Optimally you do run all the VMs on the node that own the CSV but otherwise it has less restrictions. I my humble opinion anything that restricts VM mobility is bad and goes against the grain of virtualization and dynamic optimization. I wonder if this has more to do with older CVS/Hyper-V versions, current limitations in Windows Server Hyper-V or CVS or a combination. This makes for a nice discussion, so if anyone from MSFT & the DELL Storage team responsible for Repay Manager wants to have one, just let me know Smile 

Last but not least I’d love DELL to communicate in Q4 of 2015 on how they will integrate their data protection offering in Compellent/Replay manager with Windows Server 2016 Backup changes and enhancements. That’s quite a change that’s happing for Hyper-V and it would be good for all to know what’s being done to leverage that. Another thing that is high on my priority for success is to enable leveraging replays with Live Volumes. For me that’s the biggest drawback to Live Volumes: having to chose between high/continuous availability and application consistent replays for data protection and other use cases).

I have some more things on my wish list but these are out of scope in regards to the subject of this blog post.

Remote Access to the KEMP R320 LoadMaster (DELL) via DRAC Adds Value

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If you have a virtual Loadmaster you gain a capability you do not have with an appliance: console access. You can have lost all network connectivity to the Loadmaster but you can still gain access over the Hyper-V console connection to the virtual machine. Virtual appliances are not the only or best choice for all environments and needs. When evaluating your options you should consider going for a bare metal solution like the DELL R320.

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These are basically DELL servers and as such have a Dell Remote Access Card (DRAC) that allows for remote access independently of the production network. Great for when you need to resolve an issue where you cannot connect to the unit anymore and you’re not near the Loadmaster. It also allows for remote shutdown and start capabilities, mounting images for updates, … all the good stuff. Basically it offers all the benefits of a DELL Server with a DRAC has to offer.

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That means I have an independent way into my load balancer to deal wit problems when I can no longer connect to it via the network interface or even when it is shut down. As we normally telecommute as much as possible, either from the offices, on the road or home this is a great feature to have. It sure beats driving to your data center at zero dark thirty if that is even a feasible option. image

I know that normally you put in two units for high availability but that will not cover all scenarios and if you have a data center filled with DELL PowerEdge servers that have DRAC and you cannot restore services because you cannot get to your load balancers that’s a bummer. It’s for that same reason we have IP managed PDU, OOB capabilities on the switches. The idea is to have options and be able to restore services remotely as much as possible. This is faster, cheaper and easier than going over there, so reducing that occurrence as much as possible is good. Knowledge today flies across the planet a lot faster than human being can.

DELL PowerEdge R730 Improves Boot Times

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The DELL generation 13 servers are blazingly fast and capable servers. That’s has been well documented by now and more and more people are experiencing it themselves. These are my current preferred servers due to the best value in the market for hard core, no nonsense, high performance virtualization with Hyper-V.

They also have better boot/reboot speeds than the previous generations with UEFI.  We noticed this during deployment and testing. So we decided to informally check how much things have improved.

Using the DELL DRAC8 We test the speed form Windows Server restart …

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… over the various boot phases …

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… to the visual appearance of the logon screen

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So now let’s quickly compare this for a DELL PowerEdge R720 and a PowerEdge R730. Bothe with the same amount of memory, cards, controllers etc. None of these servers had VMS running or another workload at the time of restart.

For the R720 this gave us:

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and the results for a Windows initiated server restart on a DELL PowerEdge 730 with EUFI boot is:

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This was reproducible. So we can see that we EUFI boot times have decrease with about 30%. I like that. You might think this is not important but it adds up during trouble shooting or when doing Cluster Aware Updates of a large 16+ node cluster.

Now thing are beginning to look even better as vNext of Windows has this feature call “Soft Restart” which should help us cut down on boot times even more when possible. But that’s for another blog post.

SMB Direct With RoCE in a Mixed Switches Environment

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I’ve been setting up a number of Hyper-V clusters with  Mellanox ConnectX3 Pro dual port 10Gbps Ethernet cards. These Mellanox cards provide a nice amount of queues (128) for DVMQ and also give us RDMA/SMB Direct capabilities for CSV & live migration traffic.

Mixed Switches Environments

Now RoCE and DCB is a learning curve for all of us and not for the faint of heart. DCB configuration is non trivial, certainly not across multiple hops and different switches. Some say it’s to be avoided or can’t be done.

You can only get away with a single pair of (uniform) switches in smaller deployments. On top of that I’m seeing more and more different types of switches being used to optimize value, so it’s not just a lab exercise to do this. Combine this with the fact that DCB is an unavoidable technology in networking, unless it get’s replaced with something better and easier, and you might as well try and learn. So I did.

Well right now I’m successfully seeing RoCE traffic going across cluster nodes spread over different racks in different rows at excellent speeds. The core switches are DELL Force10 S4810 and the rack switches are PowerConnect 8132Fs. By borrowing an approach from spine/leave designs this setup delivers bandwidth where they need it a a price point they can afford. They don’t need more expensive switches for the rack or the core as these do support DCB and give the port count needed at the best price point.  This isn’t supposed to be the top in non blocking network design. Nope but what’s available & affordable today in you hands is better than perfection tomorrow. On top of that this is a functional learning experience for all involved.

We see some pause frames being sent once in a while and this doesn’t impact speed that very much. It does guarantee lossless traffic which is what we need for RoCE. When we live migrate 300GB worth of memory across the nodes in the different racks we get great results. It varies a bit depending on the load the switches & switch ports are under but that’s to be expected.

Now tests have shown us that we can live migrate just as fast with non RDMA 10Gbps as we can with RDMA leveraging “only” Multichannel. So why even bother? The name of the game low latency and preserving CPU cycles for SQL Server or storage traffic over SMB3. Why? We can just buy more CPUs/Cores. Great, easy & fast right? But then with SQL licensing comes into play and it becomes very expensive. Also storage scenarios under heavy load are not where you want to drop packets.

Will this matter in your environment? Great question! It depends on your environment. Sometimes RDMA is needed/warranted, sometimes it isn’t. But the Mellanox cards are price competitive and why not test and learn right? That’s time well spent and prepares you for the future.

But what if it goes wrong … ah well if the nodes fail to connect over RDAM you still have Multichannel and if the DCB stuff turns out not to be what you need or can handle, turn it of and you’ll be good.

RoCE stuff to test: Routing

Some claim it can’t be done reliably. But hey they said that for non uniform switch environments too Winking smile. So will it all fall apart and will we need to standardize on iWarp in the future?  Maybe, but isn’t DCB the technology used for lossless, high performance environments (FCoE but also iSCSI) so why would not iWarp not need it. Sure it works without it quite well. So does iSCSI right, up to a point? I see these comments a lot more form virtualization admins that have a hard time doing DCB (I’m one so I do sympathize) than I see it from hard core network engineers. As I have RoCE cards and they have become routable now with the latest firmware and drivers I’d love to try and see if I can make RoCE v2 or Routable RoCE work over different types of switches but unless some one is going to sponsor the hardware I can’t even start doing that. Anyway, lossless is the name of the game whether it’s iWarp or RoCE. Who know what we’ll be doing in 5 years? 100Gbps iWarp & iSCSI both covered by DCB vNext while FC, FCoE, Infiniband & RoCE have fallen into oblivion? We’ll see.