How to use more than 3 virtual disks in Linux using CentOS and XenServer
- by 010110110101
I've attached 5 virtual disks to a Virtual Machine in Citrix XenServer. The VM has the xs-tools installed. Initially it said that it couldn't add so many disks. After I installed the xs-tools, it let me add all the disks.
But /dev doesn't show all the disks. It shows these:
/dev/xvda
/dev/xvdb
/dev/xvdc
/dev/cdrom
Perhaps it is bound by the limits of an IDE bus? (3 disks + CD-ROM) If so, how does one change the VM to use SCSI?
Edit:
According to the documentation:
2.6.3. VM Block Devices
In the PV Linux case, block devices are passed through as PV devices.
XenServer does not attempt to emulate SCSI or IDE, but instead
provides a more suitable interface in the virtual environment in the
form of xvd* devices. It is also possible to get an sd* device using
the same mechanism, where the PV driver inside the VM takes over the
SCSI device namespace. This is not desirable so it is best to use xvd*
where possible for PV guests (this is the default for Debian and
RHEL).
For Windows or other fully virtualized guests, XenServer emulates an
IDE bus in the form of an hd* device. When using Windows, installing
the Citrix Tools for Virtual Machines installs a special PV driver
that works in a similar way to Linux, except in the fully virtualized
environment.
Still, with 5 virtual disks attached, I don't see the other xvd devices.
Edit #2: (attached requested info)
Host Machine:
XenServer 6.1
Linux version 2.6.32.43-0.4.1.xs1.6.10.777.170770xen (geeko@buildhost) (gcc version 4.1.2 20080704 (Red Hat 4.1.2-51)) #1 SMP Wed Apr 17 05:52:03 EDT 2013
Guest Machine:
CentOS release 6.4 (Final)
Linux version 2.6.32-358.6.2.el6.x86_64 ([email protected]) (gcc version 4.4.7 20120313 (Red Hat 4.4.7-3) (GCC) ) #1 SMP Thu May 16 20:59:36 UTC 2013
Output of 'fdisk -l' on Guest Machine:
Note, the disk beyond the first 3 attached are not displaying -- there should be 4 100GB disks. (There are a total of 5 disks displayed in XenCenter -- 16GB, 100GB, 100GB, 100GB, 100GB)
Disk /dev/xvdb: 107.4 GB, 107374182400 bytes
255 heads, 63 sectors/track, 13054 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0xfb6c95b9
Device Boot Start End Blocks Id System
/dev/xvdb1 1 13054 104856223+ 83 Linux
Disk /dev/xvda: 17.2 GB, 17179869184 bytes
255 heads, 63 sectors/track, 2088 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x000e5f41
Device Boot Start End Blocks Id System
/dev/xvda1 * 1 64 512000 83 Linux
Partition 1 does not end on cylinder boundary.
/dev/xvda2 64 2089 16264192 8e Linux LVM
Disk /dev/xvdc: 107.4 GB, 107374182400 bytes
255 heads, 63 sectors/track, 13054 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0xed249ced
Device Boot Start End Blocks Id System
/dev/xvdc1 1 13054 104856223+ 83 Linux
Disk /dev/mapper/vg_blue-lv_root: 14.6 GB, 14571012096 bytes
255 heads, 63 sectors/track, 1771 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000
Disk /dev/mapper/vg_blue-lv_swap: 2080 MB, 2080374784 bytes
255 heads, 63 sectors/track, 252 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000
I see that the Linux versions say SMP. The Guest VM doesn't say "xen" in the name. However, I have already run yum install kernel-xen. Could be a clue?
