This is my first post on blog, I am still new to this thing.
I am creating this blog to store all useful topics which I need frequently as a part of interview preparation, I also feel this blog could be useful for people who wants to shift their career into Storage QA or appearing for an interview with any storage based company.
I will sincerely appreciate your comments or suggestion.
Thanks
Swapnil Deshmukh
We will start with basics of disk and storage.
Hard Drive interface comparisons (IDE & SCSI)
IDE: Advanced Technology Attachment (ATA) is a standard interface for connecting storage devices such as hard disks, and CD-ROMS drives inside personal computers.
SATA: Serial Advanced Technology Attachment is a computer bus primarily designed for transfer of data between a computer and mass storage devices.
The main advantages over the older ATA interface are faster data transfer, ability to remove or add devices while operating (hot swapping).
1. The IDE interface is cheap, generally built into the motherboard of the PC.
2. SCSI is faster, SCSI's main benefit is its ability to allow multiple accesses to the hard disk-- multiple users / applications, all accessing the hard disk at the same time, usually it is recommended to server class machines.
3. IDE only allows 2 or 4 hard disks &/or CDs per PC.
IDE is also limited to ONLY hard disks or CDs or to a similar stuff like ZIP drives and backup tape drives.
4. SCSI on the other hand, lets you connect to multiple things, the list of things you can connect to a SCSI is huge, compared to IDE.
JBOD & Storage Arrays:
JBOD: Just a Bunch of Disks, Generally used for shared storage or additional storage to particular server using FC cables
Storage Arrays: A typical storage array have following components.
1. Two Array Controllers
2. HBA Adaptors, Ethernet connectors
3. Embedded Operating System
4. Disk Drives
What is LUN: A logical unit number (LUN) is a unique identifier used on a SCSI bus that enables it to differentiate between separate devices (each of which is a logical unit). Each LUN is a unique number that identifies a specific logical unit, which may be an end user, a file or an application program.
What is DAS, NAS & SAN
DAS: Direct-attached storage (DAS) is computer storage that is directly attached to one computer or server.
NAS: Network Attached Storage follows a client/server design. A single hardware device, often called the NAS box or NAS head connected in your LAN, These NAS devices require no monitor, keyboard or mouse. acts as the interface between the NAS and network clients. They generally run an embedded operating system rather than a full-featured OS. One or more disk (and possibly tape) drives can be attached to NAS systems to increase total capacity.
Clients generally access a NAS over an Ethernet connection. The NAS appears on the network as a single "node" that is the IP address of the head device.
A NAS can store any data that appears in the form of files, such as email boxes, Web content, remote system backups, and so on. Overall, the uses of a NAS parallel those of traditional file servers.
Example of NAS: NetApp FAS 270
SAN: A SAN is a dedicated network that is separate from LANs and WANs. It is generally used to connect all the storage resources connected to various servers. It consists of a collection of SAN Hardware and SAN software; the hardware typically has high inter-connection rates between the various storage devices and the software manages, monitors and configures the SAN.
In simple terms: You can connect your server class machine into SAN environment with the help of FC cables and switch, your storage array should be connected same switch where your servers are connected.
LUN represents separate disks on your client machine .
You can assign LUNS to your server by using iSCSI initiator (for ethernet connection) and using Fibre cable and FC switch in case of SAN.
1 comment:
good start!!
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