Difference Between

Major difference between Linux yum and up2date command

The following table lists up2date and rpm commands used on earlier versions of Red Hat Enterprise Linux and their yum equivalents for use on Red Hat Enterprise Linux 5 and later.

Check for and update all RPM(S) up2date -u

Check for and update specified RPM(s) up2date -u [ ...]

Install the specified RPM(s) up2date -i [ ...]

Remove the specified RPM(s) and it’s dependents rpm -e [ ...]

Search for packages by name up2date –showall | grep “

Difference between soft link and hard link

Hard Links :

1. All Links have same inode number.

2.ls -l command shows all the links with the link column(Second) shows No. of links.

3. Links have actual file contents

4.Removing any link ,just reduces the link count , but doesn’t affect other links.

Soft Links(Symbolic Links) :

1.Links have different inode numbers.

2. ls -l command shows all links with second column value 1 and the link points to original file.

3. Link has the path for original file and not the contents.

4.Removing soft link doesn’t affect anything but removing original file ,the link becomes “dangling” link which points to nonexistant file.

Difference between soft and hard nfs mount

You get NFS timeouts because you are using soft mounts. Normally, mounts are hard, which requires the client to continue attempts to reach the server forever. A soft mount allows the client to stop trying an operation after a period of time. A soft timeout may cause silent data corruption if it occurs during data or metadata transmissions, so you should only use soft mounts in the cases where client responsiveness is more important than data integrity.

This is a UNIX terminology as to what the client does when it can’t talk to an NFS Server. If you just mount a file system without specifying hard or soft, the default is a hard mount. Hard mounts are preferable because of the stateless nature of NFS. If a client sends an I/O request to the server (such as an ls -la), and the server gets rebooted, the client will wait until the server comes back on line. This preserves data transfers in the event of a server failure. There are disadvantages to this, as a simple mount request could hang. A soft link will return with an error and fail. This kills the wait time, but can cause problems with data transfers.

Difference between FC SAN, ISCSI SAN, DAS and NAS

SAN Advantages

• Share storage among different application servers.
• Data is stored at a block level.
• Physical elements of the SAN (servers, switches, storage arrays, etc.) are connected with Fibre Channel.
• SAN is scalability and flexibility.
• Storage can be added without disrupting the applications and different types of storage can be added to the pool.
• Backups is centralized so reducing workload and providing greater assurance that the backups are complete.
• Backup traffic never impacts users on the LAN.

ISCSI SAN Advantages

• iSCSI is a lower cost alternative to Fibre Channel SAN infrastructure.
• Interconnect is Ethernet cable and the switches are Gigabit Ethernet.
• Protocol used is TCP/IP.

• iSCSI presents volumes as a block storage device which makes them ideal for use by enterprise applications such as Microsoft Exchange and Microsoft SQL Server. In particular, the Microsoft iSCSI Software Initiator is the component of the overall iSCSI environment that makes it possible to make the iSCSI SAN attached disks appear to be local attached disks.

DAS (Direct Attached Storage) Advantages

• The disks may be internal to the server or  in an array that is connected directly to the server.
• Backups must either be performed on each individual server.
• Storage can only be added by taking down the application server then adding physical disks and then rebuilding the storage. array.

NAS (Network Attached Storage) Advantages

• NAS accesses data by file.
• NAS manages its own file system.
• NAS can be accesses across multiple operating systems.
• NAS backups are more efficient. (With NAS feature called Snapshot provides an almost instantaneous way for the systems administrator to recover lost, deleted, or corrupted files.)
• Administrators can assign shares, security settings as they would for a regular file server.