# Limitations

The following are a few limitations that you can encounter while using Block Storage:

* We guarantee operation for the selected operating systems until the vendor or upstream support is available.
* Microsoft Windows Server versions are also supported until vendor support is available. For more information, see [<mark style="color:blue;">Prerequisites</mark>](/cloud/backup-and-storage/block-storage/overview/prerequisites.md).
* The following volume minimum and maximum values apply based on the storage type.

| **Storage Volume**                   | **HDD Storage** | **SSD Premium**                                                         | **SSD Standard**                                                        |
| ------------------------------------ | --------------- | ----------------------------------------------------------------------- | ----------------------------------------------------------------------- |
| Minimum size per volume              | 1 GB            | 1 GB                                                                    | 1 GB                                                                    |
| Maximum size per volume              | 4 TB            | 4 TB                                                                    | 4 TB                                                                    |
| Maximum Read/write speed, sequential | -               | 600 Mb/s per volume at 1 MB block size                                  | 300 Mb/s per volume at 1 MB block size                                  |
| Maximum Read speed, full random      | -               | 45,000 IOPS at 4 KB block size and minimum 4 Cores, 4 GB RAM per volume | 24,000 IOPS at 4 KB block size and minimum 2 Cores, 2 GB RAM per volume |
| Maximum Write speed, full random     | -               | 30,000 IOPS at 4 KB block size and minimum 4 Cores, 4 GB RAM per volume | 18,000 IOPS at 4 KB block size and minimum 2 Cores, 2 GB RAM per volume |

Larger volumes can be made available on request. For more information, contact [<mark style="color:blue;">IONOS CLOUD Support</mark>](https://docs.ionos.com/cloud/support/general-information/contact-information).


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