Posts Tagged ‘OpenManage’

Dell PowerVault MD3000i balancing virtual disks between RAID controllers

Friday, September 17th, 2010

The Dell PowerVault MD3000i iSCSI SAN has a pair of redundant RAID controller modules designed to maximise availability of the mission critical data held in your Storage Area Network. These RAID controller modules can work in a pseudo active/active mode through a bit of a work around, however there seems to be some confusion on the Dell mailing lists and forums as to exactly what is required in order to balance the load across the two RAID controller modules.

There are references to creating two sets of both the physical disks via the disk groups (the actual RAID sets) and the virtual disks (the part of each RAID set exported as a LUNs) in order to split the load between the two RAID controller modules, as each can only be active on a single RAID controller module at once.

It turns out that it isn’t necessary to create separate disk groups in order to split the physical disks across the two RAID controller modules, as each RAID controller module has access to all of the disks in the system and both of the RAID controller modules can talk to the same disks at once.

Instead, what you should do (if possible) is two create a pair of virtual disks in your disk group (or multiple disks groups if you want to utilise different RAID levels for different virtual disks). When more than one virtual disk exists, the Dell PowerVault MD300i will automatically balance the virtual disks across the RAID controller modules in a round robin fashion in order to try and spread the read/write load between the two RAID controller modules.

Although each RAID controller module is master for it’s own virtual disk, it can still pick up the virtual disk(s) off the other RAID controller module should one fail and so still provides a redundant, highly available storage system.

You can view the details of how the virtual disks are currently distributed across the RAID controller modules by going to “Support” and then “View Storage Array Profile” in the Dell Modular Disk Storage Manager software. The “Virtual Disks” tab lists the “Preferred owner” as well as the “Current owner” for each virtual disk.

Retrieve the Dell PowerEdge Service Tag remotely from Windows or Linux

Saturday, June 19th, 2010

Have you ever wanted to get the Dell Service Tag from a PowerEdge machine that you don’t have physical access to? Well it’s actually quite easy as Dell make this available through the standardised Desktop Management Interface (otherwise known as DMI) framework, so you don’t even have to install any of Dell’s OpenManage tools to view it!

On a Linux system, you just need to run the following as root:

/usr/sbin/dmidecode -s system-serial-number

On a Windows box, you can accomplish the same thing from the command prompt with:

wmic bios get serialnumber

Both of these tools should be installed by default on the respective operating system. If you have some kind of super stripped down installation, then they are available from the vendor’s original media.

Intel VT Virtualisation Technology on Dell PowerEdge servers

Saturday, June 19th, 2010

Somewhat annoyingly, Dell seem to like to disable Intel’s VT (Virtualisation Technology, sometimes called VMX) in the BIOS on their Dell PowerEdge servers, which means that you can’t use the Xen hypervisor to virtualise Microsoft Windows Server without changing this setting, which requires a reboot of the server to take effect.
You can use omreport from the Dell OpenManage Server Administrator software to check whether or not you have Intel Virtualisation Technology enabled.
If you haven’t got OpenManaged Server Administrator installed, then you can enable the Dell yum repository for CentOS/Red Hat systems and install it with:

wget -q -O – | bash
yum -y install srvadmin-base
/opt/dell/srvadmin/sbin/ start

Once you’ve got the Dell OpenManage Server Administrator services running, you can take a look at what processor is installed in your system and what the current BIOS settings are with:

omreport chassis processors
omreport chassis biossetup

The two attributes that you’re looking for are Processor Virtualization Technology (which needs to be enabled) and Demand-Based Power Management (which needs to be disabled).

If you need to change them, then you can do this with:

omconfig chassis biossetup attribute=cpuvt setting=enabled
omconfig chassis biossetup attribute=dbs setting=disabled
omreport chassis biossetup again and then once you’ve rebooted the server you can start taking advantage of the hardware virtualisation provided by Intel’s Virtualisation Technology.