Thursday, November 13, 2008

Storage System

Physical Volume: Name for an actual disk e.g SSA, SCSI disk; a PV can belong to a VG only

Volume Group: It is the largest unit of storage allocation; It contains multiple PV under a single VG name. The combined storage of all the PV makes a total space of VG which is used in turn by File Systems and Logical Volumes. A VG is splitted into PP; the size of PP within VG remains constant.

Why to create separate VG? e.g datavg and rootvg.
ans: To separate userdata from OS files; Disaster Recovery; Data portability; Data integrity and security | Maintenance is easy because you can update or reinstall OS without restoring data.
You can make VG unavailable using VARRYOFFVG.
There can be 255 VGs per System.

Physical Partition: PP is the division of PV. It is the basic unit of disk space allocation.
Default max no. of PP per PV is 1016. PP size cannot be changes dynamically but the number of PP per PV can be changed dynamically in mulitples of 1016. (i.e 1016, 2032, ...)

(Note: If you increase the more than 1016 PP per PV, then no. of PV per VG will be reduced)

Logical Volume: LV contains one or more LP within the VG. LV may span the PV if the multiple PV within the VG. LV size may be increased dynamically using SMIT even when users are working on that LV. However, the size cannot be reduced easily.

MAX PV=32 (128 BIG VG)
MAX LV=255 (512 BIG VG)
MAX VG =255 per system

Logical Partition: LP within a VG is the same size as PP

LVM does mapping between LV (logical view of storage) and PV (actual view of storage).

Why LVM?

In traditional Storage System, there were many limitation:

1. Requirement of Contiguous Disk Space
2. Max partition size=Max Disk size (i.e Partition size cannot span multiple disks)
Thus no file system can be larger than Disk size
3. Pre-plan the partition size requirement, as after creation of partition, the partition cannot be resized.

To tackle with these problems, LVM (Logical Volume Manager) was developed.

Benefits of LVM:

1. LV solves the non-contiguous disk space requirement
2. LV can span to mulitiple disks
3. Dynamically increase LV size
4. LV can be mirrored
5. Harddisk easily added to the system.
6. LV can be relocated.

Tuesday, November 11, 2008

SAN storage

SAN (Storage Area Network):

Why SAN?

How many drives your standalone PC can have?
ans: 2-3

Is that enough for the organization?
ans: of course not

If you lose your drive, what happens?
ans: total disaster, u lose all your data

ok then, SAN has all the solution...
Make Storage section consisting huge array of drives and allocate LUNs (Logical Unit Number) to the clients as per they demand.
Like One of my client need 2 GB for rootvg of AIX server. Then I allocate 1 LUN of 2 GB and give to the client.

Following is the connection configuration in SAN:

[100s of clients]-----HIGH SPEED FIBRE CHANNEL----[Tera byte storage]

Clients get access to their LUN via Fibre Channel and thus can be said that they are physically connected.


For Redundancy RAID is implemented

RAID 0 --- striping (for high performance)
RAID 1 --- mirroring (for safe side operation i.e even a single drive fails, u still have another as backup)
RAID 5 --- parity bit enabled (data recovery even if one disk failed)

What about NAS?
NAS is similar thing, but it uses Ethernet instead of Fibre Channel. So NAS is slower than SAN.

Following is the connection configurtion in NAS



Linux boots in 2.97 seconds

Eat your heart out, Microsoft

SOFTWARE ENGINEERS at Japan's embedded Linux software vendor Lineo announced technology last week that can boot a low-power computer system within 2.97 seconds, the company claims.

Lineo calls its quick-start software system Warp 2, apparently either never having heard of IBM's ill-fated and abandoned OS/2 Warp operating system or not being particularly superstitious.

The company says Warp 2 consists of a bootloader, a customised Linux software stack, and a 'hibernation driver' similar to familiar suspend-to-disk software. Lineo's innovation is that its hibernation driver writes a snapshot of RAM into flash memory instead of to a hard disk.

The Warp 2 implementation is reportedly able to save multiple alternative system snapshots to enable rebooting either into a clean startup environment or to a previously saved session.

The hibernation driver is also capable of compressing the saved RAM image by about 50 per cent, depending upon what it contains. One of its demonstration tests reduced a 32MB RAM image to 19MB, Lineo claims.

In benchmark tests using an ARM CPU, a small low-power system running Warp 2 – with Linux, an X display subsystem, the tiny window manager twm and three xterm command line shells – booted an uncompressed 18.3MB RAM image in 2.97 seconds. Reportedly the system booted the same test suite from a compressed 6.8MB RAM image in 3.17 seconds.

Nearly instant-on Linux based systems are becoming common throughout the PC industry.

ASUS announced last May that it had begun preloading a BIOS flash embedded Linux and web browser system, called Express Gate, with all of the computer motherboards it ships.

That technology is based on DeviceVM Splashtop, which HP and Lenovo are reportedly also adopting. Dell Latitude On is a Montavista Linux system that runs on a separate ARM CPU. Not to be outdone, Toshiba and Intervideo have Linux based quick-boot systems too.

Moreover, the best-selling segment of the PC market now is netbooks – lightweight, small notebook style PCs that can handle light web browsing, email, photos and even streaming audio and video, practically as well as larger laptop and desktop PCs. Reportedly up to 25 per cent of netbooks run Linux, and Linux based fast-boot technology is ideally suited for the way people use those systems.

After all, no one needs to lug around a bulky laptop loaded down with heavyweight legacy software just to wibble the web, manage their email and photos, use their work-related, cloud-based software applications, and keep up with their social not-working addictions.

Less than two weeks ago Jim Zemlin, the executive director of the Linux Foundation, took note of all these developments and predicted that Linux will outship Windows next year.

That's not only possible but likely, we think, given that it looks like Linux will be shipping on a lot of PCs that are also loaded with Windows, and considering the better reliability and security, ease of use, and lower costs of Linux based systems, especially on netbooks.

The giant Vole of Redmond seems to be turning into an aging, slow dinosaur, surrounded by a quickly growing population of faster, smaller, and more agile little Linux mammals. ยต