--- name: BlockStorage-getting-started title: Getting started with Block Storage for Classic description: Block Storage for Classic delivers enterprise-grade durability and availability with flexible performance options through persistent iSCSI-based block storage. last-updated: 2026-08-07 --- > ## Documentation Index > The table of contents for this documentation set is at https://cloud.ibm.com/docs/BlockStorage?format=markdown > The index for all IBM Cloud docs is at: https://cloud.ibm.com/docs/llms.txt > Use these files to discover more information as needed. {: ui-linked} # Getting started with Block Storage for Classic {: #getting-started} {: toc-content-type="tutorial"} {: toc-services=""} {: toc-completion-time="2h"} Block Storage for Classic delivers enterprise-grade durability and availability with flexible performance options through persistent iSCSI-based block storage. {: shortdesc} IBM Cloud® Block Storage for Classic is persistent, high-performance iSCSI storage that is provisioned and managed independently of Compute instances. iSCSI-based Block Storage for Classic volumes are connected to authorized devices through redundant multi-path I/O (MPIO) connections. Block Storage for Classic brings best-in-class levels of durability and availability with an unmatched feature set. It is built by using industry standards and best practices. Block Storage for Classic is designed to protect the integrity of the data and maintain availability through maintenance events and unplanned failures, and provide a consistent performance baseline. For more information about using Block Storage for Classic with the IBM Cloud® Kubernetes Service, see [Storing data on classic IBM Cloud Block Storage](https://cloud.ibm.com/docs/containers?topic=containers-block_storage&format=markdown). ## Before you begin {: #prereqs} {: step} Block Storage for Classic volumes can be provisioned from 20 GB to 12 TB with two options: - Provision **Endurance** tiers that feature pre-defined performance levels and other features like snapshots and replication. The following 4 tiers are available: - `LOW_INTENSITY_TIER` = 0.25 IOPS/GB - `READHEAVY_TIER` = 2 IOPS/GB - `WRITEHEAVY_TIER` = 4 IOPS/GB - `10_IOPS_PER_GB` = 10 IOPS/GB - Build a high-powered **Performance** environment with allocated input/output operations per second (IOPS). For more information about the Block Storage for Classic offering, see [What is Block Storage for Classic](https://www.ibm.com/products/block-storage){: external}. ## Provisioning considerations {: #provconsiderBlock} {: step} ### Block size {: #blocksizeBlock} IOPS for both Endurance and Performance is based on a 16-KB IO size with a 50-50 read and write, 50-50 random and sequential workload. A 16-KB block is the equivalent of one write operation to the volume. {: important} The IO size that is used by your application directly impacts the storage performance. If the IO size that is used by your application is smaller than 16 KB, the IOPS limit is realized before the throughput limit. Conversely, if the IO size that is used by your application is larger than 16 KB, the throughput limit is realized before the IOPS limit. | IO Size (KB) | IOPS | Throughput (MB/s) | |-----|-----|-----| | 4 | 1,000 | 4 | | 8 | 1,000 | 8 | | 16 | 1,000 | 16 | | 32 | 500 | 16 | | 64 | 250 | 16 | | 128 | 128 | 16 | | 512 | 32 | 16 | | 1024 | 16 | 16 | {: caption="Table contains examples of how block size and IOPS affect the throughput. Average IO size x IOPS = Throughput in MB/s." caption-side="bottom"} ### Authorized hosts {: #numberofhosts} Another factor to consider is the number of hosts that are using your volume. IOPS limits are enforced at the volume level. In other words, two hosts connected to a volume with 6000 IOPS share that 6000 IOPS. At high IOPS counts, especially at extreme IOPS counts (10,000s), you must use several hosts to access the volume simultaneously to realize the maximum IOPS available. The maximum IOPS for a block storage volume is 48,000 IOPS. If your workload requires high throughput, it's best to configure at least a couple servers to access your volume to avoid a single-server bottleneck. The default limit for the number of authorizations per block volume is eight. That means that up to eight hosts can be authorized to access the Block Storage for Classic volume. For more information about authorization and increasing the limit of 8, see the [FAQs](https://cloud.ibm.com/docs/BlockStorage?topic=BlockStorage-block-storage-faqs&format=markdown#authlimit). ### Network connection {: #networkconnectivity} The speed of your Ethernet connection must be faster than the expected maximum throughput from your volume. Generally, don't expect to saturate your Ethernet connection beyond 70% of the available bandwidth. For example, if you have 6,000 IOPS and are using a 16-KB IO size, the volume can handle approximately 94-MBps throughput. If you have a 1-Gbps Ethernet connection to your volume, it becomes a bottleneck when your servers attempt to use the maximum available throughput. It's because 70% of the theoretical limit of a 1-Gbps Ethernet connection (125 MB per second) would allow for 88 MB per second only. To achieve maximum IOPS, adequate network resources need to be in place. Other considerations include private network usage outside of storage, and host-side and application-specific tunings (IP stack or [queue depths](https://cloud.ibm.com/docs/BlockStorage?topic=BlockStorage-hostqueuesettings&format=markdown), and other settings). Storage traffic ought to be isolated from other traffic types, and not be directed through firewalls and routers. For more information, see the [FAQ](https://cloud.ibm.com/docs/BlockStorage?topic=BlockStorage-block-storage-faqs&format=markdown#isolatedstoragetraffic). Storage traffic is included in the total network usage of Public virtual servers. For more information about the limits that can be imposed by the service, see the [virtual server Documentation](https://cloud.ibm.com/docs/virtual-servers?topic=virtual-servers-about-virtual-servers&format=markdown). {: tip} ## Submitting your order {: #submitorder} {: step} When you're ready to submit your order, you can place it in the [console](https://cloud.ibm.com/docs/BlockStorage?topic=BlockStorage-orderingBlockStorage&interface=ui&format=markdown#orderingthroughConsole), from the [CLI](https://cloud.ibm.com/docs/BlockStorage?topic=BlockStorage-orderingBlockStorage&interface=cli&format=markdown#orderingthroughCLI), with the [API](https://cloud.ibm.com/docs/BlockStorage?topic=BlockStorage-orderingBlockStorage&interface=api&format=markdown#orderingthroughAPI), or [Terraform](https://cloud.ibm.com/docs/BlockStorage?topic=BlockStorage-orderingBlockStorage&interface=terraform&format=markdown#orderingthroughTerraform). By default, you can provision a combined total of 700 Block Storage for Classic and File Storage for Classic volumes globally. If you require more storage, see [Managing storage limits](https://cloud.ibm.com/docs/BlockStorage?topic=BlockStorage-managingstoragelimits&format=markdown). {: note} ## Connecting and configuring your new storage {: #mountingstorage} {: step} When your provisioning request is complete, authorize your hosts to access the new storage, and configure your connection. Depending on your host's operating system, follow the appropriate link. - [RHEL 9]{: tag-linux} [Mount iSCSI volume on Red Hat Enterprise Linux® 9](https://cloud.ibm.com/docs/BlockStorage?topic=BlockStorage-mountingRHEL&format=markdown). - [CloudLinux 8]{: tag-linux} [Mount iSCSI volume on CloudLinux 8](https://cloud.ibm.com/docs/BlockStorage?topic=BlockStorage-mountingCloudLin8&format=markdown). - [Ubuntu 24]{: tag-linux} [Mount iSCSI volume on Ubuntu OS](https://cloud.ibm.com/docs/BlockStorage?topic=BlockStorage-mountingUbuntu&format=markdown). - [Windows]{: tag-windows}[Mapping volumes on Microsoft Windows](https://cloud.ibm.com/docs/BlockStorage?topic=BlockStorage-mountingWindows&format=markdown). - [cPanel]{: tag-app}[Configuring Block Storage for Classic for backup with cPanel](https://cloud.ibm.com/docs/BlockStorage?topic=BlockStorage-cPanelBackups&format=markdown). - [Plesk]{: tag-app} [Configuring Block Storage for Classic for backup with Plesk](https://cloud.ibm.com/docs/BlockStorage?topic=BlockStorage-PleskBackups&format=markdown). ## Managing your new storage {: #managingnewstorage} {: step} In the console, from the CLI, with the API, or Terraform, you can manage various aspects of your Block Storage for Classic such as host authorizations and cancellations. For more information, see [Managing Block Storage for Classic](https://cloud.ibm.com/docs/BlockStorage?topic=BlockStorage-managingstorage&format=markdown). You can keep your data synchronized across two different locations by using replication. Replication uses one of your snapshot schedules to copy snapshots automatically to a destination volume in a remote data center. You can recover the copies from the remote site if a catastrophic event occurs or your data becomes corrupted. For more information, see [Replication and Disaster Recovery – Replicating Data](https://cloud.ibm.com/docs/BlockStorage?topic=BlockStorage-replication&interface=ui&format=markdown). If you are planning to expand your IBM Cloud infrastructure or evaluate modern storage options, see [Migrating data from IBM Cloud classic infrastructure to VPC](https://cloud.ibm.com/docs/classic-to-vpc?topic=classic-to-vpc-data-migration-classic-to-vpc&format=markdown).