We are living in a trend of remote System Administration and in real-time we rarely touch and feel a server that we are managing for 24×7 ( 24 Hours a Day and 7 days a Week). Although we don’t really deal with our servers physically,  it is always better to know about the hardware that we have to support remotely. The Physical Server hardware awareness helps us for quick decision-making during the hardware troubleshooting. 

A decade ago, when I was learning my system administration course,  the most challenging task for me is imagine about how a real-time servers looks like and  how those servers are different from regular PCs. I couldn’t touch and feel a real server until I joined to my first job as UNIX admin and the server is Enterprise 450 ( a real elephant in shape and weight).

Today, Sysadmin learners are lucky enough to watch the real-time servers before they actually work on it, and the courtesy and credit goes to Oracle. Below are some of the important and powerful servers from oracle which are available in market for mission critical UNIX environment.

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I came across one unique parameter which I would like to share on our gurkulindia, specially for small business organisations where we dont have seperate power backups for DC.

Has anyone noticed while working on Solaris boxes if you will power down (init 5 or poweroff from LOM/ALOM/ILOM) the Solaris boxes, they wont come up automatically after physical power on (only LOM boots but No OS). Which is a serious concern if any power outage occur or any power unit failure occurs etc etc…

Ex: Suppose a power outage occurred in any DC and 100 Solaris boxes went down. Now after power restoration, you wont be able to see any Solaris Box up and running. Manual intervention is required and SA need to power on the boxes manually from LOM prompt. Practically this situation is highly unacceptable in any organisation and this is the default feature of Solaris.

After a long investigation and googling and PDF’s I safely landed on earth and the landmark is below. There is a parameter on LOM/ALOM (for Sparc arch.) and ILOM (for intel arch.) which you wont find in help. The default value for that parameter is FALSE which wont allow your OS instance to boot up and hence it just stuck and wait for manual intervention at LOM level only.

I have tested the same in large scaled Solaris environment while performing hardware replacements & upgrades, when the value is FALSE the server stuck at LOM and OS wont come up, on the other hand if the value is changed to TRUE and power restored the Box comes up. Read Full

System Controller battery (BATTERY at SC/BAT/V_BAT has exceeded low warning) failure in T-series servers.

Many a times you will get a hardware error in /var/adm/messages (or at ALOM/LOM prompt, console messages) for SC battery failure, In this post I will explain the battery replacement procedure along with its importance in the system.

sc> showfaults -v
Last POST run: THU AUG 09 11:08:20 2012
POST status: Passed all devices

  ID Time              FRU               Fault
   0 AUG 09 11:05:54   SC/BAT            BATTERY at SC/BAT/V_BAT has exceeded low warning threshold.

Importance:

Battery in T-series model is located on System Controller (SC) and system downtime is required to replace the battery.

The system controller contains the persistent storage for the host ID and Ethernet MAC addresses of the system, as well as the ALOM CMT configuration including the IP addresses and ALOM CMT user accounts, if configured.

Battery provides power to the System Controller NVRAM when no AC power  is applied to the system.

Note:

After SC battery replacement the date/time on the SC/host will set to default value as shown below, the same will reflect in the hosts UPTIME too if you wont set the date/time correctly after battery replacement:

sc> showdate
SAT JAN 01 00:06:55 UTC 2000 Read Full

Our Unixadmin, John from xyz company,  recently upgraded one of his server’s network interface card  from the old one with 100MB speed to a new one with 10Gig speed , and the reason is to improve the speed for the backup of the server. After the NIC Upgrade  john found that the server network performance was improved a little, but still the server is not able to utilize all the available network bandwidth. 

After a bit of investigation john realised that his server TCP window size has to be tuned  to utilize maximum network bandwidth available to the server.  In this post we will be discussing the procedure about “how john tuned the TCP window size  to increase his server network performance?”.

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Let us assume that our system administrator Jack is supporting for a server environment in which a small set of servers  are located in DMZ (Demilitarized zone ) network . In order to connect any DMZ server Jack has to ssh from his machine (windows PC/Unix workstation) to another server which acts as gateway between internal network and  DMZ network, and then he has to SSH to the DMZ server that he want to connect.

 Just to make his life easy to support these DMZ servers for his day-to-day system administration tasks, Jack wants to create a special encrypted tunnel from Jack’s host to the DMZ server.  He wants to achieve this goal by using the secured internal server (i.e. server1) as tunnel server between his PC/workstation and DMZ server.

 Jack’s Network Setup for SSH tunnel:

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Virtual LANs or VLANs are virtual separations within a switch that provide distinct logical LANs that each behave if there were configured on a separate physical switch. Some Important points about VLANS.

•  All the servers connected with in a VLAN will have same broadcasting domain, and can connect to each other directly
•  Servers belongs to different VLANs has to communicate with each other using external Routing device.  
•  To Expand the VLAN across multiple physical switches, physical switches needs to be interconnected using links called Trunks

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