Logical Volume Manager in RHEL 6: Part1

Logical Volume Manager also known as LVM is one of the most important topic, not only for the RHCSA exam preparation but also for the real environment System Administration. In production environment the disk partitioning is mostly based on LVM because of facilities and ease provided by Linux Logical Volume Manager. LVM provide facility to create partitions flexibly. For example using LVM we can make a volume group using a chunk of hard-disks, and from that volume we can create partitions as required. LVM gives System Administrator, power to extend or reduce the partitions online, means we can extend a logical volume while the data on it is being accessed by the users, without corruption of data.

It is important to understand the basic concept of LVM. There are mainly three steps(points) to create LVM:

• Physical Volume:- Actual hard-disk or a partition of disk.
• Volume Group :- Group of one or more than one physical Partition(s).
• Logical Volume :- Partition created from Volume Group.

LVM in RHEL 6

 In the above example there are three disks (can also use partitions of disk) made as Physical Volume(PV), lets say size of each Physical Volume be 20 GB. From these three Physical volumes we create a Volume Group(VG), so the size of that Volume Group is 20 x 3 = 60 GB. From that Volume Group we can create multiple Logical Volumes (partitions) of different sizes or a single partition of 60 GB. We can use the whole volume group at a time, or can use create partitions when required. 

Lets take a simple example: We have created a Volume Group named VGDATA of size 60 GB using three 20 GB Physical Volumes. From Volume Group "VGDATA" we created two Logical Volumes "lvdata1" and "lvdata2" each of size 30 GB and mounted them on /data1 and /data2 respectively. After a period of time we feel that directory /data2 is getting full and need more space, we can do that by adding a new hard-disk of size 25 GB and making it a Physical Volume. Now we can extend the Volume Group VGDATA by adding the new Physical Volume to it. So now size of VGDATA becomes 85 GB. Now we can extend the Logical Volume "lvdata2" to appropriate size.

This is a general overview of Redhat Enterprise Linux Logical Volume Manager (LVM). In the next post we will learn commands and process to create LVMs'.

For any questions or quires please comment.

RHCSA FEES UPDATE...

This Diwali, Redhat gives you special offers on certifications. There are two schemes for RHCSA + RHCE certifications form 5 September to 22nd November.

SCHEME 1 :- "FESTIVAL DOUBLE BLAST"

Applicable from 5th September 2011 - 20th November 2011)

"RHCSA + RHCE" at INR 15,000/- with free second attempt on RHCSA or RHCE or both *

SCHEME 2 :- "FESTIVAL DOUBLE BLAST WITH VIRTUALIZATION"

 Applicable from 5th September 2011 - 20th November 2011)

"RHCSA + RHCE" at INR 19,900/- with free second attempt on RHCSA or RHCE or both
& “RHCVA” single attempt at just INR 100/- *"

* Terms and Conditions
1. This scheme is applicable only for candidates who have undergone Red Hat (RHEL 6) official curriculum training.
2. This scheme is applicable only for candidates who register for any one of the above mentioned schemes between 5th September 2011 & 20th November 2011.
3. The fee and offer is as follows:
SCHEME EXAM FEE OFFER
RHCSA + RHCE (Double Attempt) INR 15,000/- "RHCSA + RHCE" at INR 15,000/- with free second
attempt on RHCSA or RHCE or both

RHCSA + RHCE (Double Attempt) & RHCVA (Single Attempt) INR 20,000/- (INR 19,900/- + INR 100/-)

"RHCSA + RHCE" at INR 19,900/- with free second attempt on RHCSA or RHCE or both & “RHCVA” single attempt at INR 100/- *
4. The last date to register for any one scheme is 20th November 2011.
5. The last date to appear for first attempt of RHCSA & RHCE exam is 25th November 2011.
6. The last date to appear for second attempt of RHCSA & RHCE exam is 30th November 2011.
7. The last date to appear for RHCVA exam is 31st December 2011.
8. The fees has to submitted minimum 7 days before the examination day to Red Hat India Pvt. Ltd.,
9. The examination fee is non refundable.
10. Once registered and scheduled, no change in the examination date is possible.
11. Once registered, the candidate cannot replace themselves with another prospect.
12. It is mandatory for students registering for either scheme to attempt RHCSA & RHCE examinations first time on the same day.

RHCSA

Documents required to register:
◦ Certification exam discount coupon of SAI & SAII for RHCSA.
◦ Certification exam discount coupon of SAI, SAII and SAIII for RHCE.
◦ Certification exam discount coupon of RHEV for RHCVA.
◦ It is mandatory to provide Govt. issued ID card such as Driving License, Passport, Voter ID card, etc., on the day of the exam, in original.
◦ Candidates registering for either scheme must submit 3 passport size photographs.
◦ All the forms should be completely furnished by the student and signed by the concerned center manager/
director and sealed by the training institute where the participant has undergone training.

Please note:
If the candidate has availed the discount, but fails to produce the registration form and discount voucher on the day of examination, he would forfeit the exam fee paid and would not be allowed to appear to the examination. Those candidates who have registered for any scheme cannot claim any refund, if they get certified as RHCSA or RHCE or both in the first attempt.

Dates to Remember
• Last date to register for any scheme: 20th November, 2011
• Last date to appear for first attempt of RHCSA & RHCE: 25th November, 2011
• Last date to appear for second attempt of RHCSA & RHCE: 30th November, 2011
• Last date to appear for first attempt of RHCVA: 31st December, 2011