How to present 6TB of LUN to Windows Server

I attached 6TB of ISCSI lun to my VCB backup server and after attaching this is  what I found under diskmgmt.msc

I then checked if the VOL has been split across by SAN admin but that was not the case. This was the part of same VOL so why does WIN2K3 show it as two VOL of 2 and 4TB.

After that I realize with MBR I can have only 2TB of lun and if I need to get all 6TB of LUN I need to convert the disk into GPT(GUID Partition Table).

How to do it  ? Just right click on the disk and you will get option “convert to GPT disk”

What I have read and understood is

MBR is the standard partitioning scheme that's been used on hard disks since the PC first came out. It supports 4 primary partitions per hard drive, and a maximum partition size of 2TB.

GPT disks are new, and are readable only by Windows Server 2003 SP1, Windows Vista (all versions), and Windows XP x64 Edition. The GPT disk itself can support a volume up to 2^64 blocks in length. (For 512-byte blocks, this is 9.44 ZB - zettabytes. 1 ZB is 1 billion terabytes). It can also support theoretically unlimited partitions.

Windows restricts these limits further to 256 TB for a single partition (NTFS limit), and 128 partitions.

Only Itanium systems running Windows Server 2003 and Windows Vista systems with an EFI BIOS can boot from a GPT disk. The other operating systems mentioned earlier can use GPT disks as data disks but not boot disks.

To find out more about GPT read this article from MS.

How to reset password for root on Ubantu

Yes I have started learning Ubantu. I installed Ubantu8.1 desktop and during installation it ask me to create user name but never prompt me for root password. So once I logged in I was not sure what would be the root password.

When I did su ,it asked me for password.
So now I was in fix how to change password for root.

To change password /reset password
:~$ sudo sh

it will ask for current logged in user password

Then you will be in # prompt.

Type here passwd and it will change password for root

How to find out which HBA is connected on ESX host

I wanted to figure out how to find out which HBA is connected /cabled. I had been using Qlogic QLE406X and usually I used to press Ctrl + S to configure using BIOS. This way I use to ping the target to find out which port has been cabled.

Reason is we don’t cable all the available port and ESX is not kind enough to tell you which port is what. It does select randomly vmhba 0,1,2,3,4

I asked the same question to Vmware support but could not find any clue. Finally I found answer on Qlogic download site. Next go to http://www.qlogic.com downloads section, select your iSCSI HBA and choose Linux Red Hat (32-bit) from the select menu.

Download the SANsurfer iscli (x86/Intel 64) file (Latest available from the site) to your local machine. Unzip the file to a folder. Browse the datastore and upload the entire folder

SSH into the box and CD to the location where the folder has been uploaded . You will find following files under it

We have to install “iscli-1.2.00-15_linux_i386.rpm ”. To install this use following command

[root@xxxx]# rpm -ivh iscli-1.2.00-15_linux_i386.rpm

Preparing... ########################################### [100%]

1:iscli ########################################### [100%]

Installation completed successfully.

Now type command iscli , this will start nice interactive menu to configure/troubleshoot/update firmware for HBA

From the menu select the option 7 and then choose HBA which are detected by ESX host. Which ever HBA has been cabled ,link will show as UP. Select that HBA and configure it for IP and perform the ping test.

Enable/Disable maintenance mode from command line

vimsh -n -e /hostsvc/maintenance_mode_enter to enable maintenance mode

and

vimsh -n -e /hostsvc/maintenance_mode_exit to disable it

Set_rtc_mmss: when the hardware clock is out of synch with system clock

I saw following error message on the console

set_rtc_mmss: can't update from 59 to

When I ran

   [root@xxx]# hwclock -r;date

Thu 30 Oct 2008 05:22:47 AM EDT  -0.437804 seconds

Mon Aug 17 05:22:47 EDT 2009

It has the huge difference between system clock and H/W clock

I then ran 

  [root@xxx]# hwclock –systohc

And now the time difference is pretty low

[root@xxxx]# hwclock -r;date

Mon 17 Aug 2009 05:26:21 AM EDT  -0.026283 seconds

Mon Aug 17 05:26:20 EDT 2009