Boot from SAN environments
Boot-from-SAN environments offer several advantages, including high performance, redundancy, and space consolidation. In these environments, the boot disk is on a remote SAN and not on the local host. The host communicates with the SAN through a host bus adapter (HBA). The HBA’s BIOS contains the instructions that enable the host to find the boot disk.
Boot from SAN depends on SAN-based disk arrays with either hardware Fibre Channel or HBA iSCSI adapter support on the host. For a fully redundant boot from SAN environment, you must configure multiple paths for I/O access. To do so, ensure that the root device has multipath support enabled. For information about whether multipath is available for your SAN environment, consult your storage vendor or administrator. If you have multiple paths available, you can enable multipathing in your XenServer deployment upon installation.
Boot-from-SAN settings are not inherited during the upgrade process. When upgrading using the ISO or network-boot, follow the same instructions as used in the installation process below to ensure that
multipathis correctly configured.
To install XenServer to a remote disk on a SAN with multipathing enabled:
On the Welcome to XenServer screen, press F2.
At the boot prompt, enter
The XenServer installation process configures the XenServer host, which boots from a remote SAN with multipathing enabled.
To enable file system multipathing using PXE or UEFI installation, add
device_mapper_multipath=yes to your configuration file. The following is an example configuration:
default xenserver label xenserver kernel mboot.c32 append /tftpboot/xenserver/xen.gz dom0_max_vcpus=1-2 \ dom0_mem=1024M,max:1024M com1=115200,8n1 \ console=com1,vga --- /tftpboot/xenserver/vmlinuz \ xencons=hvc console=hvc0 console=tty0 \ device_mapper_multipath=yes \ install --- /tftpboot/xenserver/install.img
For additional information on storage multipathing in your XenServer environment, see the XenServer Administrator’s Guide.
Software-boot-from-iSCSI for Cisco UCS
The Software-boot-from-iSCSI feature enables customers to install and boot XenServer from SAN using iSCSI. Using this feature, XenServer can be installed to, booted from, and run from a LUN provided by an iSCSI target. The iSCSI target is specified in the iSCSI Boot Firmware Table. This capability allows the root disk to be attached through iSCSI.
XenServer supports the following features for Software-boot-from-iSCSI:
Host installation through PXE-boot
Cisco UCS vNIC
Software-boot-from-iSCSI has been tested in Legacy BIOS and UEFI boot mode by using Cisco UCS vNICs and Power Vault, NetApp, and EqualLogic arrays. Other configurations might work, however, they have not been validated.
Jumbo Frames (MTU=9000) configured with the Cisco UCS manager
Cisco UCS line-rate limiting
Networks using the vSwitch back-end
LVHDoISCSI SRs and NFS SRs on the same or different SAN/NAS
Multipathing of the iSCSI root disk
Compatibility with common XenServer (Network, Maintenance) operations
The primary management interface (IP addressable) and the network for VM traffic, must use separate interfaces.
Storage (iSCSI targets) must be on a separate Layer 3 (IP) network to all other network interfaces with IP addresses on the host.
Storage must be on the same subnet as the storage interface of the XenServer host.
Install XenServer by using CD media
Perform the following steps to install XenServer using a CD:
Access the boot menu; at the
Use the cursor keys to select an installation option:
For a single path LUN, select install
For a multipathed LUN, select multipath
Press the tab key.
Edit the line ending with the following:
Using the cursor keys, edit this line to read:
use_ibft --- /install.img
XenServer host installation proceeds as normal.
Install XenServer by using PXE
Perform the following steps to install XenServer using PXE:
Ensure that you add the keyword use_ibft in the kernel parameters. If multipathing is required, you must add device_mapper_multipath=enabled.
The following example shows PXE configuration for a single LUN:
label xenserver kernel mboot.c32 append XS/xen.gz dom0_max_vcpus=2 dom0_mem=1024M,max:1024M com1=115200,8n1 console=com1,vga --- XS/vmlinuz xencons=hvc console=tty0 console=hvc0 use_ibft --- XS/install.img
The following example shows PXE configuration for a multipathed LUN:
label xenserver kernel mboot.c32 append XS/xen.gz dom0_max_vcpus=2 dom0_mem=1024M,max:1024M com1=115200,8n1 console=com1,vga --- XS/vmlinuz xencons=hvc console=tty0 console=hvc0 use_ibft device_mapper_multipath=enabled --- XS/install.img