Old DRS and new DRS

[Bab]

I was read this article about new DRS :

https://www.vmware.com/content/dam/digitalmarketing/vmware/en/pdf/techpaper/performance/drs-vsphere7-perf.pdf

1- As I understand old DRS runs every 5min for example when contention occured at 3:30 and DRS run in this time it had to vMotion till 3:35 and next DRS run 3:35

is that correct?

2- will be do vMotion in the 5 min between 3:00 - 3:35 or vMotion will be do in the next five min between 3:35 - 3:40 ?)

3- Will do DRS and vMotion in the same time ?

In New DRS which runs every 1 min , I am confused for 1min :

4- When we change the thresholds level to 5 or 4 or 3 there is no difference ? another run every 1 min?

for example when have contention and run at 3:00 it runs and do vMition another run 3:01 and run DRS and vMotion ad continuously .....

5- What does this mean in the document ?

The new DRS generally recommends lighter VMs (in terms of their memory usage), whereas the old DRS recommends heavier VMs in general. (Is that mans in vSphere7 DRS will be do better performance for vms with lower Memory for example VM1 with 10G and VM2 with 32G memory . Does new DRS prefer to vMotion and balance vm1 instead of vm2 ?

BR

[Scott Vessey]

Moderator: Thread moved to the vSphere area given the subject matter.

[amohammadimir]

1,2,3: As you already know prior to vSphere 7, VMware DRS evaluates your cluster every 5 minutes. If there’s an imbalance in load it will reorganize your cluster, with the help of vMotion, to create an evenly balanced cluster again. So, every 5 minutes DRS run invokes and initiate VM Migration(if it is fully automated).

One thing to mention, DRS run could invoke before contention occurs. For example a DRS run invoked at 3:29 then CPU contention starts at 3:30 and creates an imbalance in the cluster. So, the next DRS run invokes at 3:34.

4: This threshold can increase or decrease the number of migrations and it's not related to the time of DRS run.

5. The old DRS was Cluster Centric and the new DRS is Workload Centric. According to that they recommend different types of VMs for vMotion during load balancing. Hence, in general it's true.

[Bab]

Thanks,

1-but want to know in prior DRS every 5 min just evaluate resource on cluster and do vMotion if need in this 5minutes or just evaluate in 5min and in the next DRS will be do vMotion ?

2- in the new DRS , imagine we have 3 hosts that  memory usage for host1= 30% , host2=32% , host3=33% but the score of one of vm is 20 (vm resourse is 4vcpu and 8G memory) as we have enough resource on al of hosts thus this is not relate to the DRS and will not solve with vMotion and had to add memory to the vm is that correct ?

3- As I understood new DRS will be do with follow conditions:

3-1: while we have two vms with different resources vm1 with 6G memory and vm2 with 32G memory in the first step it prefer do vMotion for vm1 that has lower resource even vm2 meet contention in the first step it vMotion vm1 till vm2 can use more resource of that host.

3:2: the second condition is that is account vMotion cost for example in that time if do vMotion the system's workload may increase and problem not solve

3:3: and finally review cluster resource such as old DRS try to keep balance resource between hosts

Is that correct ?

BR

[Bab]

Is that correct ?

[Bab]

Would you please help ?

[Scott Vessey]

Moderator: Please be patient, VMTN is a community forum and those helping usually do so voluntarily in their own time.