Monthly Archives: May 2010

How to share Terminal with screen command.

>This articles step in to tell how to share the terminal with screen commands to provide demonstration like if I type anything on my screen, the same will reflect on the screen of other person who are logged on my system with my shared username.

Here are the steps, you need to follow.

The first user who wants to share his screen has to follow the following practices –


1) Setting up the setuid & permission to write on /var/run/screen for user.
sudo chmod +s /usr/bin/screen
sudo chmod 755 /var/run/screen

2) Put the terminal in screen mode i.e honey
screen -S honey
3) Press the CTRL & A and type the following lines

CTRL-A
:multiuser on

4) Add the user in ACL so that he/she can see the terminal

CTRL-A
:acladd username

The End user who wants to see the shared terminal.

1) Login to the system with SSH for said user (username) like below and provide the password.

ssh username@mysystem ( provide the password)

2) Once logged in, type the following command to get the terminal shared.

screen -x username/honey

Note– honey is name of screen which is shared on point 2.

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VMware – VMFS SAN LUNs Architectural & Planning

>Since there are a way around to architectural and planning a SAN Luns while preparing with VMware environment and provides the VMFS partition for the same.

Here we can get an idea with the following formula. hopefully it might help.

ESX/ESXi Server Configuration –

1) Total No of VM Machines planned to run on individual ESX/ESXi Server – 8

2) Total amount of disk space required for each VM Machines required – 14G

3) Total Storage Capacity required for this Operation – 112G ( 8*14G)

4)Total number of VM Machines planned to deploy on VMware Envirnoment – 200

5)Total Storage Space required for this capacity Planning is – 2800G (200 VM * 14G ) – (Total number of VM Machines planned to deploy on VMware Envirnoment/Total amount of disk space required for each VM Machines required)

6)Total number of ESX/ESXi required for this capacity planning is – 25 (Total number of VM Machines planned to deploy on VMware Envirnoment/Total No of VM Machines planned to run on individual ESX/ESXi Server)

7)Total number of cluster is – 2 ( Two)

8)Number of servers per cluster are – 12/13 ( Total number of ESX/ESXi required for this capacity planning/Total number of cluster is)

Cluster Configuration –

9)Total VM Machines per Cluster – 100

10)Total Storage capacity is – 1400G (Total Storage Space required for this capacity Planning is/Total number of cluster is)

High I/O LUNs Disk Sizing –

11) Total LUNS for disk intensive VMs machines(Total VM Machines per Cluster/32) = 100/32 =3.13

12 )Total size per VM machines with 20% growth – 569G (Total Storage capacity is/3 * 0.20)

VMware – VMFS Notes

>These are the following notes while might be helpful for VMware Enthusiastic.

Note :

1) VMFS can support LUNs with max size of 2TB, Suppose if we need 4 or 6 TB luns then we can distribute like 2*2TB.
2) Up to 100 non-IO-intensive VMs can share a single VMFS volume with acceptable performance.
3) No more than 255 files per VMFS partition.
4) Up to 2TB limit per physical extent of a VMFS volume. There are 32 extent we can add on a VMFS filesytem.

What do you mean by extent here.Let me eloborate it –

VMFS filesytem works on the LVM concent like LVM support ‘8e’ filesytem the same way VMFS filesystem support ‘fb’ filesytem. The extent
here represents the block of disk as it was referred in disk concept.

5) Allows access by multiple ESX Servers at the same time by implementing per-file locking. SCSI Reservations are only implemented when LUN meta data is updated (e.g. file name change, file size change, etc.)
6) Add or delete an ESX Server from a VMware VMFS volume without disrupting other ESX Server hosts just because of shared disk storage as only CPU and Memory stats are associated with ESX server only.
7) LVM allows for adaptive block sizing and addressing for growing files allows you to increase a VMFS volume on the fly (by spanning multiple VMFS volumes)
8)With ESX/ESXi4 VMFS volumes also can be expanded using LUN expansion
9)Optimize your virtual machine I/O with adjustable volume, disk, file and block sizes.
10)Recover virtual machines faster and more reliably in the event of server failure with Distributed journaling.
11) VMFS file size ( Block size)
1 MB = 256 GB
2 MB = 512 GB
4 MB = 1024 GB
8 GB = 2048 GB
(Max vmdk filesize on VMFS partition is 2TB.)

12) Recommended limit of 16 ESX servers per VMFS volume,based on limitations of a VirtualCenter-managed ESX setup.
Note:

a) A VMFS volumn can be shared with upto 32 ESX Servers.
b) Recommended maximum of 32 IO-intensive VMs sharing a VMFS volume.