Adding RAM on the fly

As with CPUs, the possibility to add memory on the fly is an added value in mission-critical environments where downtime can literally cost a company millions of Euros.

The recipe presented here is quite simple, similar to the one on CPUs. Here, your guest needs to be prepared to use this functionality as well.

Getting ready

If you want to be able to add memory on the fly to a guest, it must be configured to support it. As with the CPU, this has to be activated. There are three ways to do this:

The guest must be created with the maxmem option, as follows:
```
--memory 2G,maxmemory=4G
```

You can set the maximum memory using the virsh command, as follows:

~]# virsh setmaxmem --domain <guestname> --size <max mem> --live

You can edit the guests' XML files:
```
~]# virsh edit <guestname>
```

Of course, the latter 2 option requires you to shut down the guest, which is not always possible in production environments.

Ensure that the guests' XML configuration files contain the following elements with the subsequent attributes:

<domain type='kvm'>
...
    <memory unit='KiB'>4194304</memory>
    <currentMemory unit='KiB'>2097152</currentMemory>
...
</domain>

How to do it…

Let's increase the guest's memory.

On the KVM host, perform the following steps:

Get the current and maximum memory allocation for a guest, as follows:

~]# virsh dumpxml srv00002 |grep -i memory
  <memory unit='KiB'>4194304</memory>
  <currentMemory unit='KiB'>4194304</currentMemory>

Set the new amount of memory for the guest by executing the following command:
```
~]# virsh setmem --domain <guestname> --size <memory> --live
```

On the KVM guest, perform the following:

Tell your guest OS about the memory increase through this command:

~]# for i in $(grep -H offline /sys/devices/system/memory/memory*/state | awk -F: '{print $1}'); do echo online > $i; done

Tech Concepts

Programming languages

Tech Tools

Unlimited access to the largest independent learning library in tech of over 8,000 expert-authored tech books and videos.

Innovative learning tools, including AI book assistants, code context explainers, and text-to-speech.

50+ new titles added per month and exclusive early access to books as they are being written.

Red Hat Enterprise Linux Server Cookbook

By : Jakub Gaj, Leemans

Red Hat Enterprise Linux Server Cookbook

By: Jakub Gaj, Leemans

Overview of this book

Adding RAM on the fly

Getting ready

How to do it…

Red Hat Enterprise Linux Server Cookbook

By : Jakub Gaj, Leemans

Red Hat Enterprise Linux Server Cookbook

By: Jakub Gaj, Leemans

Overview of this book

Adding RAM on the fly

Getting ready

How to do it…

Confirmation

Buy this book with your credits?

Submit Your Feedback

Create a Free Account To Continue Reading

Sign in to activate your 7-day free access