Thursday, April 19, 2007

load and stress testing

One of the most common, but unfortunate misuse of terminology is treating "load testing" and "stress testing" as synonymous. The consequence of this ignorant semantic abuse is usually that the systemis neither properly "load tested" nor subjected to a meaningful stresstest.
1. Stress testing is subjecting a system to an unreasonable load while denying it the resources (e.g., RAM, disc, mips, interrupts, etc.) needed to process that load. The idea is to stress a system tothe breaking point in order to find bugs that will make that break potentially harmful. The system is not expected to process the overload without adequate resources, but to behave (e.g., fail) in a decent manner (e.g., not corrupting or losing data). Bugs and failuremodes discovered under stress testing may or may not be repaireddepending on the application, the failure mode, consequences, etc. The load (incoming transaction stream) in stress testing is often deliberately distorted so as to force the system into resource depletion
2. Load testing is subjecting a system to a statistically representative (usually) load. The two main reasons for using such loads is in support of software reliability testing and in performance testing. The term "load testing" by itself is too vagueand imprecise to warrant use. For example, do you mean representativeload," "overload," "high load," etc. In performance testing, load is varied from a minimum (zero) to the maximum level the system can sustain without running out of resources or having, transactions suffer (application-specific) excessive delay.
3. A third use of the term is as a test whose objective is to determine the maximum sustainable load the system can handle. In this usage, "load testing" is merely testing at the highest transaction arrival rate in performance testing.

Stress Testing: Stress testing is designed to test the software with abnormal situations. Stress testing attempts to find the limits at which the system will fail through abnormal quantity or frequency of inputs. For example,Higher rates of interrupts, Test cases that require maximum memory or other resources,Test cases that cause 'thrashing' in a virtual operating system, Test cases that cause excessive 'hunting' for data on disk systems etc.Load Testing: The application is tested against heavy loads or inputs such as testing of web sites in order to find out at what point the web-site/application fails or at what point its performance degrades. In load testing, response time, think time, throughput, workload etc is analyzed

Thursday, April 12, 2007

System Administrator

The Role of the System Administrator

RealLegal iBinder uses projects from the desktop RealLegal Binder and Publisher applications to create Web-based projects. Your role as the system administrator is to create and upload projects, grant users access to projects, determine how search results display, and give users specific rights pertaining to projects.
Conversely, users can open projects, update projects, view transcripts, and assign issues and annotations. If you give them the rights to do so, they can also download and print transcripts.
1. Determine Who Can Update a Project:

By default, all users can a update a project. As a system administrator, you should learn how project update works, determine if some or all users should not have the right to update a project, and then update the settings accordingly. For more information refer to Overview of Synchronization (Project Update) and Denying Specific Users Synchronization Rights.

2.Monitoring All Access
the SiteAs a system administrator, you can monitor all access to the site. Refer to Overview of Monitoring for more information.
Two types of monitoring exist in iBinder:
You have the option to monitor what transcripts and exhibits are downloaded. Use this when you want to bill people for downloads.
You have the option to monitor system activity. For example, you can monitor which users login to a project, and you can monitor administrative activity, such as at what time and on what day you denied a user access to iBinder.


3. Deleting Transcripts and Exhibits:

To reduce a project's size or to get rid of unneeded transcripts and/or exhibits, you can delete transcripts and exhibits from iBinder. You can also rename a transcript or an exhibit.

4. Granting Access to Projects
One of your responsibilities is to add users to a project and then grant those users access to the project. To grant a user access, toggle the Open option to Yes on the Configure—Users page.

5. How Search Results Display
Users may request that you adjust how QA (Question & Answer) pairs display in a report. Use the Advanced tab accessible from the Options page to provide more or less text around QA pairs that displays in a search report.

6. E-Commerce
You can set up RealLegal iBinder to track who downloads transcripts and exhibits, and you can notify users that they will be charged each time they view a transcript. You can then view a log of who viewed transcripts and notify your billing department to bill them. For instructions, refer to the Logs topic.


Wednesday, April 11, 2007

LILO (boot loader)

LILO (LInux LOader) is a generic boot loader for Linux.LILO was originally developed by Werner Almesberger, while its current developer is John Coffman.
LILO does not depend on a specific file system, and can boot an operating system (e.g., Linux kernel images) from floppy disks and hard disks. One of up to sixteen different images can be selected at boot time.
Various parameters, such as the root device, can be set independently for each kernel. LILO can be placed either in the master boot record (MBR) or the boot sector of a partition.
In the latter case something else must be placed in the MBR to load LILO.At system start, only the BIOS drivers are available for LILO to access hard disks. For this reason, with very old BIOSes, the accessible area is limited to cylinders 0 to 1023 of the first two hard disks. For later BIOSes, LILO can use 32-bit "logical block addressing" (LBA) to access practically the entire storage of all the harddisks that the BIOS allows access to.LILO was the default bootloader for most Linux distributions in the years after the popularity of loadlin. Lately it has become a second choice in favour of the GRUB bootloader.
lilo installs a boot loader that will be activated next time you boot. It has lots of options.
-v
Increase verbosity. Giving one or more -v options will make lilo more verbose.
-q
List the currently mapped files. lilo maintains a file, by default /boot/map, containing the name and location of the kernel(s) to boot. This option will list the names therein.
-m map-file
Use specified map file instead of the default.
-C config-file
lilo reads its instructions about what files to map from its config file, by default /etc/lilo.conf. This option can be used to specify a non-default config file.
-d delay
If you have specified several kernels, and press Shift at boot-time, the boot loader will present you with a choice of which system to boot. After a timeout period the first kernel in the list is booted. This option specifies the timeout delay in deciseconds.
-D label
Use the kernel with the given label, instead of the first one in the list, as the default kernel to boot.
-r root-directory
Before doing anything else, do a chroot to the indicated directory. Used for repairing a setup from a boot floppy.
-t
Test only. Do not really write a new boot sector or map file. Use together with -v to find out what lilo is about to do.
-c
Enable map compaction. This will merge read requests from adjacent sectors. Speeds up the booting (especially from floppy).
-f disk-tab
Specify disk geometry parameter file. (The default is /etc/disktab.)
-i boot-sector
Specify a file to be used as the new boot sector. (The default is /boot/boot.b.)
-l
Generate linear sector addresses instead of sector/head/cylinder addresses.
-L
Generate 32-bit Logical Block Addresses instead of C:H:S addresses, allowing access to all partitions on disks greater than 8.4Gb.
-P {fixignore}
Fix (or ignore) `corrupt' partition tables, i.e., partition tables with linear and sector/head/cylinder addresses that do not correspond.
-s save-file
When lilo overwrites the boot sector, it preserves the old contents in a file, by default /boot/boot.NNNN where NNNN depends on the device. This option specifies an alternate save file for the boot sector. (Or, together with the -u option, specifies from where to restore the boot sector.)
-S save-file
Normally, lilo will not overwrite an existing save file. This options says that overwriting is allowed.
-u device-name
Uninstall lilo, by copying the saved boot sector back. A time-stamp is checked.
-U device-name
Idem, but do not check the time-stamp.
-R command line
This option sets the default command for the boot loader the next time it executes. The boot loader will then erase this line: this is a once-only command. It is typically used in reboot scripts, just before calling `shutdown -r'.
-I label
The label of the running kernel can be found in the environment variable BOOT_IMAGE after startup. This command will print the corresponding path name on stdout.
-V
Print version number.
The above command line options correspond to the key words in the config file indicated below.
-b bootdev
boot=bootdev
-c
compact
-d dsec
delay=dsec
-D label
default=label
-i bootsector
install=bootsector
-f file
disktab=file
-l
linear
-L
lba32
-m mapfile
map=mapfile
-P fix
fix-table
-P ignore
ignore-table
-s file
backup=file
-S file
force-backup=file
-v
verbose=level