Understanding Instance Storage on IBM Cloud Virtual Servers for VPC

2 min read

Instance storage on IBM Virtual Servers for VPC is an excellent option for fast, affordable, temporary storage that is widely used among developers for their cloud-native workloads and services. 

Instance storage is a storage technology that is complementary to, and can be used alongside, VPC's block storage volumes. 


Block storage boot and data volume lifecycles persist independently from the virtual server instance to which they might be attached. By contrast, the lifecycle of instance storage is tied directly to the lifecycle of the virtual server instance with which it was provisioned. 

When the virtual server is shut down or deleted, the instance storage attached to the virtual server instance is cryptographically erased, and the instance storage is no longer available. The virtual server's boot and data volumes are not affected. The temporary nature of instance storage makes it an ideal storage option for Distributed File Systems, Content Delivery Networks (CDNs) and temporary files created during transaction processing. 


The performance of instance storage exceeds that of block storage. It scales linearly based on the amount of storage consumed, thereby providing a consistent performance profile. This scaling is determined by the amount of storage that is provided to the instance. 

By using Quality of Service, the IOPs and bandwidth are scaled based on the amount of disk that is used. Rate limits are placed individually on each disk. If you use multiple disks, speeds might be improved by striping the data across the disks.

Instance storage is available in the Balance, Compute, Memory, Very High Memory and Ultra High Memory virtual server and dedicated host profile families. You can expect the following approximate performance results:

  • Read IOPs: ~200 IOPs per GiB, up to approximately 300k IOPs total
  • Write IOPs: ~65 IOPs per GiB, up to approximately 75 IOPs total
  • Read bandwidth: 0.85 MiB/GiB
  • Write bandwidth: 0.85 MiB/GiB

FIO performance benchmark example

FIO benchmarks were run against several different Balance family profile types with instance storage. The tests were run with a simple synthetic benchmark balancing the I/O across all disks, with the following results. As you can see, the scaling of the virtual service instances are linear until the caps are observed on the IOPs:

Instance storage FIO performance benchmark example.

Instance storage FIO performance benchmark example.

Most workloads don't have a unified I/O pattern and mix random small block operations with sequential large block operations. As such, your workload might see different results that are based on its unique I/O pattern. Therefore, your performance might vary depending on the characteristics of your workload. 

With a solid understanding of the lifecycle and performance characteristics of the disk, instance storage on IBM Virtual Servers for Virtual Private Cloud (VPC) can be a helpful component to improve the performance of your cloud workloads.

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