10.4. Storage Domain Limitations

Storage domains provide space for the storage of virtual disk images and ISO images as well as the import and export of virtual machines. While many storage domains may be created within a given data center, there are a number of limitations and recommendations that apply to each storage domain.

Table 10.2. Storage Domain Limitations

Item Limitations
Storage Types
Supported storage types are:
  • Fibre Channel Protocol (FCP)
  • Internet Small Computer System Interface (iSCSI)
  • Network File System (NFS)
  • POSIX Compliant File System (POSIX)
  • Red Hat Gluster Storage (GlusterFS)
New ISO and export storage domains in Red Hat Virtualization 4.0 can be provided by any file-based storage (NFS, Posix or GlusterFS).
Logical Unit Numbers (LUNs) No more than 300 LUNs are permitted for each storage domain that is provided by iSCSI or FCP.
Logical Volumes (LVs)
In Red Hat Virtualization, logical volumes represent virtual disks for virtual machines, templates, and virtual machine snapshots.
No more than 350 logical volumes are recommended for each storage domain that is provided by iSCSI or FCP. If the number of logical volumes in a given storage domain exceeds this number, splitting available storage into separate storage domains with no more than 350 logical volumes each is recommended.
The root cause of this limitation is the size of LVM metadata. As the number of logical volumes increases, the LVM metadata associated with those logical volumes also increases. When this metadata exceeds 1 MB in size, the performance of provisioning operations such as creating new disks or snapshots decreases, and lvextend operations for thinly provisioning a logical volume when running a QCOW disk take longer to run.
Further detail about logical volumes is available in https://access.redhat.com/solutions/441203.

Note

See Storage in the Administration Guide for further information about storage domains.