Difference between BLOCK and FILE level Data : -Ashwin

Block refers to Physical level, the way OS interacts with Disk-Drive, simplest example would be "OS interacting with local SCSI Harddrive in our home/office pc" . It deals with block of disk, there is no file-system attached to it. Clients can not read and interepret block-data if there is no internediate file system like ..NTFS, FAT, Ext3 etc.

SQL and Exchange: Are highly write and read intesive databases, in other words, they need faster processing because they process many read and write requests, (Online Transaction Processing) and thats why they deal in "Blocks". Therefore SQL and Exchange database is not recommended on "NAS" or "FIle servers", because these file servers are usually accessed as a mapped or UNC path and the data is moved via "TCP/IP" network and it deals in "File Level" protocol such as "CIFS/SAMBA" for Windows and NFS for (UNIX/Linux) paltforms which is not suitable for Databases applications.Block storage is normally abstracted by a file system or database management system to talk to clients or endusers.


Block based databases requires : Locally attached disk array Or SAN data centers.


File Level Data: The data which has file system attached, for example: a word document , is a file level data and is backedup along with this meta data. This is where NAS / Netapp / Windows Storage Server comes in to picture, they are basically "Read" intesive boxes. They are not meant for intensive writing, they are basically file servers providing file service (Read) to clients. For normal disk sharing between small Office / Home office this is a good option, where many users can write to and read to common "Disk" on the remote server via mapped or unc path.

File level : NAS / Netapp & Windows Storage Server.


Summary:
This file system can reside either on a server or on a NAS device. If it’s on the server, block level data is written to the disk array, usually via either an FC or iSCSI interface. If the file system is on the NAS, file level data is written to the NAS device, usually via Ethernet. The NAS device in turn writes block level data to disk. A “NAS Gateway” is a device that maintains the file system and communicates file-level data with clients on the LAN, while storing data on external FC-attached disk.

An advantage of file level data is the ease of sharing information. Because the file system resides within the NAS, any device can access and understand the data. When the file system resides in the server, only that server can retrieve data from the disk.

BLOCK vs FILE - WHAT HAPPENS UNDERNEATH

FC-SAN communicates at the block level, with requests over the "wire(fiber/copper)" like :

•Read-block-thirty-four

 

or

 

•Write-block-five-thousand-and-two

 

 

 

NAS communicates at the file level, with requests over the "wire (Ethernet)“  like:

 

 

•Create-file-MyHomework.doc

 

or

 

•Read-file-Budget.xls

 

 

 

 

The Wires being used:

• NAS solutions utilize TCP/IP based networks, such as Ethernet

 

• SAN solutions use Fibre Channel connections (Fiber/Copper)

 

 

 

 

 

The Protocols being used:

 

• NAS solutions use  iSCSI Protocol over standard Ethernet networks to talk BLOCK.

 

• SAN solutions utilizes Fibre Channel encapsulated SCSI setups

 

Affordable Windows iSCSI storage area network : Backup Exec backs up data to ISCSI drive.

How to build an affordable Windows iSCSI storage area network, Here in this article, author has shown, how Backup Exec for Windows Server can make use of "NAS" Or another Server's Hardisk as backup drive and transfer data "Block-Level" via "ISCSI" protocol. This is faster than the orthodox "TCP/IP" file-level backup.

Courtesy:
http://www.crn.com/article/printableArticle.jhtml?articleId=59201007

Interview questions for tech companies : Crack it.

Please visit the following website for any IT Support / Development / Aministrator's Job Interview Questions and Answeres.

http://www.techinterviews.com/

It's a wonderful site for those who are prepraring or in process on any forthcoming interview schedule. You can find interview related question's ranging from :

1. Exchange Domain
2. Databases.
3. Backup Administrator
4. Computer Hardware.
5. Testing.
6. Developer (C++, Java etc)
7. Networking.

Any, many more.

Courtesy: http://www.techinterviews.com/

NDMP ended the monopoly of the Backup software Vendors and File Server vendors :

With the invent of NDMP, we have only one "universal agent" for the network- attached file servers to be used by any of the centralized backup administration applications. Earlier Backup vendors had to "develop" many cleint/agent software which would understand different OSes needs,

for ex:
1. Windows agent for Windows Servers.
2. Unix angent for Unix/Linux Servers.
3. Solarix agent for Solaris Servers.
4. Mac agent for Mac Servers.


This not only led to more cost incur on the vendor side for development of these agent, but also customers had to bear the cost of so many agents, further dedicated file servers had to be mounted to such OS so that their data could be backed via NFS or CIFS (SAMBA) file level protocols. Most serious drwabacks were , data had to travel via networks to the central backup application where "tape/library" was attached.

FIler Definition: -Ashwin

Filer, is a storage device (cabinet) with an embedded processor and a "light weight" OS that exposes disk units to network-based clients (which are usually servers) . Clients that access NAS-based storage must also run some sort of redirector or client software that lets the OS see the NAS-based disk as locally attached storage.They are used in data sharing applications including the Internet, fibre channel SANs, and Ethernet LANs

Backup and Restore : By Dilip Naik

Backup is the process whereby a coherent copy of data is made. Backup has become more important as the amount of data has exploded, not just in importance, but in volume as well. One study estimates that more data will be created in the next few years than has been created since the dawn of history! It is interesting to compare the growth in data storage with the more widely known and appreciated growth in electronic chip density. Recall that Moore's law implies that the amount of electronics on a given chip area doubles every 18 months. A lot of industry analysts believe that the growth in digital storage is actually handily beating Moore's law in the sense that the amount of data doubles in much less than 18 months.

Backup and Restore Technologies:
http://searchstorage.techtarget.com/
searchStorage/downloads/Naik_ch05.pdf