Monthly Archives: October 2013

Taking vSphere to the Next Level with Converged Infrastructure – vForum2013

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At this months vForum in Sydney, Australia, I will be presenting “Taking vSphere to the Next Level with Converged Infrastructure”.

The session discusses where the virtualization market is today along with problems that exist along the journey to 100% virtual and how converged infrastructure helps solve these challenges allowing vSphere architects and administrators to take their virtual environments to the next level.

The session is scheduled for Day 2 of the conference (October 22nd) at 11AM in Parkside 110A room.

I invite everyone who will be at vForum Sydney to attend the session, and for those of you who cannot make the event, the presentation will be posted on this blog along with follow up articles covering any questions from the session.

 

Competition Example Architectural Decision Entry 4 – vCloud Allocation Pool Usable Memory

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Name: Prasenjit Sarkar
Title: Senior Member of Technical Staff
Company: VMware
Twitter: @stretchcloud
Profile: VCAP-DCD4/5,VCAP-DCA4/5,VCAP-CIA,vExpert 2012/2013

Problem Statement

When using an Allocation Pool with 100% memory reservation, due to the VM memory overhead, the usable memory is less than what is expected by the users. What is the best way to ensure users can use the entire memory assigned to the Allocation pool.

Assumptions

1. vCD 5.1.2 is in use

2. vSphere 5.1 or later is in use

3. Org VDC created with Allocation Pool

Constraints

1. vCD 5.1.2 has to be used

2. Allocation Model only VDCs are affected

Motivation

1. Need to use 100% memory allocated to the VDC with Allocation Pool model

2. Optimal use of Memory assigned to Org VDC and then to the VM

Architectural Decision

Due to the “by design” fact of VM memory overhead, we cannot use the entire allocated memory and this will be solved by enabling Elastic Allocation Pool in the vCloud System level and then set a lower vCPU Speed value (260 MHz). This will allow VMs to use the entire allocated memory (100% guarantees) in the Org VDC.

Alternatives

1. Over allocate resources to the customer but only reserve the amount they purchased.

Historically VM overhead ranges in between <=5% to 20%. Most configurations have an overhead of less than 5%, if you assume such you could over allocate resources by 5% but only reserve ~95%. The effect would be that the customer could consume up to the amount of vRAM they purchased and if they created VMs with low overhead (high vRAM allocations, low vCPU) they could possibly actually consume more than they “purchased”. In the case of a 20GHz/20GB purchase we would have to set the Allocation to 21GHz but set the reservation to 95%.

Justification

VM memory overhead is calculated with so many moving targets like the model of the CPU in the ESXi host the VM will be running on, whether 3D is enabled for MKS, etc. So you cannot use the entire allocated memory at any point in time.

By selecting the Elastic VDC, we are overwriting this behavior and still not allowing more VMs to power on from what they have entitled to. Also Elastic VDC gives us an opportunity to set a custom vCPU speed and lowering the vCPU speed will allow you to deploy more vCPUs without being penalized. Without setting this flag, you cannot overcommit the vCPU, which is really bad.

260MHz is the least vCPU speed we can set and thus this has been taken to allow system administrators to overcommit the vCPUs in a VDC with Allocation Pool.

 

Implications

1. One of the caveat is not having any memory reservation for any VMs. Due to the nature of OrgVDCs, it does not allow an Org Admin to set the resource reservation for the VMs (unlike Reservation Pool) and thus any VMs with Elasticity on will not have any reservation which will be marked as overkill for the customer’s high I/O VMs (like DB or Mail Server).

You can easily overwrite the resource reservation using the vSphere but that is not the intent. Hence, we flag it as RISK as it will hamper customer’s VM performance for sure.

If we say we are reserving 100% memory and thus spawning the VMs will get equal memory and can’t oversubscribe the memory as the limit is still what the customer has bought, then also if there is a contention of memory within those VMs, I don’t have an option to prefer those VMs which are resource hungry. In a nutshell all of the VMs will get equal share.

Equal shares will distribute the resource in a RP equally and thus there will not be any guarantee that a hungry VM can get more resource on demand.

Back to Competition Main Page or Competition Submissions

Competition Example Architectural Decision Entry 3 – Scalable network architecture for VXLAN

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Name: Prasenjit Sarkar
Title: Senior Member of Technical Staff
Company: VMware
Twitter: @stretchcloud
Profile: VCAP-DCD4/5,VCAP-DCA4/5,VCAP-CIA,vExpert 2012/2013

Problem Statement

You are moving towards scalable network architecture for your large scale Virtualized Datacenter and want to configure VXLAN in your environment. You want to make sure that Teaming Policy for VXLAN transport is configured optimally for better performance and reduce operational complexity around it.

Assumptions

1. vSphere 5.1 or greater
2. vCloud Networking & Security 5.1 or greater
3. Core & Edge Network topology is in place

Constraints

1. Should have switches that support Static Etherchannel or LACP (Dynamic Etherchannel)
2. Have to use only IP Hash Load balancing method if using vSphere 5.1
3. Cannot use Beacon Probing as Failure Detection mechanism

Motivation

1. Optimize performance for VXLAN

2. Reduce complexity where possible

3. Choosing best teaming policy for VXLAN Traffic for future scalability

Architectural Decision

LACP – Passive Mode will be chosen as the teaming policy for the VXLAN Transport.

At least two or more physical links will be aggregated using LACP in the upstream Edge switches.

Two Edge switches will be connected to each other.

ESXi host will be cross connected to these two Physical upstream switches for forming a LACP group.

LACP will be configured in Passive mode in Edge switches so that the participating ports responds to the LACP packets that it receives but does not initiate LACP negotiation.

Alternatives

1. Use LACP – Active Mode and make sure you are using IP Hash algorithm for the load balancing in your vDS if using vSphere 5.1.

2. Use LACP – Active Mode and use any of the 22 available load balancing algorithm in your vDS if using vSphere 5.5.

3. Use LACP – Active Mode and use Cisco Nexus 1000v virtual switch and use any of the 19 available load balancing algorithm.

4. Use Static Etherchannel and make sure you are using IP Hash *Only* algorithm in your vDS.

5. If using Failover then have at least one 10G NIC to handle the VXLAN traffic.

Justification

1. Fail Over teaming policy for VXLAN vmkernel NIC uses only one uplink for all VXLAN traffic. Although redundancy is available via the standby link, all available bandwidth is not used.
2. Static Etherchannel requires IP Hash Load Balancing be configured on the switching infrastructure, which uses a hashing algorithm based on source and destination IP address to determine which host uplink egress traffic should be routed through.

3. Static Etherchannel and IP Hash Load Balancing is technically very complex to implement and has a number of prerequisites and limitations, such as, you can’t use beacon probing, you can’t configure standby or unused link etc.

4. Static Etherchannel does not do pre check both the terminating ends before forming the Channel Group. So, if there are issues within two ends then traffic will never pass and vSphere will not see any acknowledgement back in it’s Distributed Switches

5. Active LACP mode places a port into an active negotiating state, in which the port initiates negotiations with other ports by sending LACP packets. If using vSphere prior to 5.5 where only IP Hash algorithm is supported then LACP will not pass any traffic if vSphere uses any other algorithm other than IP Hash (such as Virtual Port ID)

6. The operational complexity is reduced

7. If using vSphere 5.5 then can use 22 different algorithm for load balancing and also Beacon Probing can be used for Failure Detection.

Implications

1. Initial setup has a small amount of additional complexity however this is a one time task (Set & Forget)

2. Only IP Hash algorithm is supported if using vSphere 5.1

3. Only one LAG can be supported for the entire vSphere Distributed Switches if using vSphere 5.1

4. IP Hash calculation if not done manually by taking VM’s vNIC and Physical NIC then there is no guarantee that it will balance the traffic across physical links

Back to Competition Main Page or Competition Submissions