# 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>](https://docs.ionos.com/sections-test/guides/storage-and-backup/block-storage/overview/prerequisites).
* 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).