GitHub user arpanbht created a discussion: Clarification on CloudStack VM Storage Architecture (NFS Primary Storage vs KVM Host Local Storage)
Hello everyone, I have a query regarding how storage is managed for virtual machines in Apache CloudStack, specifically concerning the location of root and data disks for running VMs. In our private CloudStack setup, we have followed the official documentation to deploy the infrastructure, which includes: - A CloudStack Management Server - Multiple KVM Host machines - An NFS server configured as primary storage When we create VMs on a KVM host, we observe that the local storage of the host machine is not being utilized. Below is a sample output from one of our KVM hosts: ``` compute1@compute1:~$ df -h Filesystem Size Used Avail Use% Mounted on tmpfs 13G 4.8M 13G 1% /run /dev/sda2 878G 15G 818G 2% / tmpfs 63G 0 63G 0% /dev/shm tmpfs 5.0M 0 5.0M 0% /run/lock tmpfs 63G 0 63G 0% /run/qemu /dev/sda1 1.1G 6.1M 1.1G 1% /boot/efi 172.16.17.202:/export/primary 3.5T 2.7T 701G 80% /mnt/81ecd9fd-9cdf-34cb-b99d-51d0e2cf3a0c tmpfs 13G 4.0K 13G 1% /run/user/1000 ``` >From this, we can see that: - The NFS primary storage is mounted on the host (/mnt/...) - The local disk of the host remains largely unused (~15 GB utilized) Based on this observation, our understanding is that: - The root and data disks of VMs are being stored entirely on the NFS-based primary storage - The KVM host’s local storage is not used for VM disk storage We would appreciate confirmation on whether this understanding is correct. Additionally, we have a few concerns and questions: 1. Since all VM disk I/O appears to depend on the NFS primary storage, could this become a performance bottleneck at scale? 2. Is there a supported way in CloudStack to: - Use local storage on KVM hosts for VM root/data disks? - Or configure a hybrid approach (e.g., some VMs on NFS, others on local storage)? 3. If local storage can be used: - What changes are required in storage configuration or zone setup? - Are there any trade-offs (e.g., migration limitations, HA constraints)? We are trying to evaluate whether our current architecture is optimal for long-term scalability and performance. Any guidance, best practices, or references would be highly appreciated. GitHub link: https://github.com/apache/cloudstack/discussions/13103 ---- This is an automatically sent email for [email protected]. To unsubscribe, please send an email to: [email protected]
