Page Comparison

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N.B. Rogō is being used on Linux and Solaris servers for all known installations in the community. However, as Rogō runs on a LAMP stack there should be no issues with it running on a Windows server.

From Rogo 6Rogō 6.1 the install and update scripts will check that the listed extensions are installed before letting you proceed.

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Running on-line summative assessments requires a stable hardware platform with enough resources to handle the current student numbers and predicted growth in numbers. Rogo is Rogō is a web application based around the LAMP stack and many of the standard optimisation techniques are applicable. However, on-line summative assessments have a different load profile to normal web traffic caused by the start of the exam. This high load over a short time period and the importance of the consequence of hardware failure must be taken into account.

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CPU	1x Quadcore
RAM	4Gb
Hard Disk	8Gb (RAID recomended recommended for reliability NOT 0,2,3,4, for this size of space RAID 1 is adequate)

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CPU	2x Quadcore
RAM	8Gb
Hard Disk	20Gb (RAID recomended recommended for reliability NOT 0,2,3,4, for this size of space RAID 1 is adequate)

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Redundancy of Hardware This includes multiple PSUs (This allows either one source of power to fail or a failure of a PSU) and multiple networks (This allows either network hardware failure/routing issues or can increase the server bandwidth) along with Redundant storage solutions (allowing a disk failure to not interrupt the service and often provide higher performance than a single disk).
Availability - the design of supporting architecture should mirror the risk associated with failure. For high-stakes summative exams this normally requires a higher level of risk mitigation than simple formative self-assessments, for example. There are two main models of availability possible: 1.
1. Automatic high-
availablity
1. availability - virtual machines or load balancers are used to seamlessly flow requests between multiple servers in case of failure. In main cases the aim is that end users will not even notice that traffic has been routed to a different server. This will also require HA or cluster mysql setup.
1.
2. Manual fall-over - two machines of identical specification can be used in a 'live' and 'backup' configuration. Usually the database would be configured as 'master' on the live server and 'slave' on the backup to keep records synchronised in real-time. Files (e.g. images) can be copied between servers using cron jobs set to run each day. In the event of a failure in the live the master/slave database connection would be broken by the system administrator and students told to re-start the exam on the backup server. Worst case scenario would be that one screen of results could be lost. This is the simplest method and has been
implimented
1. implemented at Nottingham for many years without actually needing to being used.
Load - web-servers can handle thousands of users spread out over a period of time, but with summative exams high loads are imposed at the start of the exam and also we have seen at the end when students are quickly navigating between screens checking answers.
Bandwidth - the bandwidth required will depend on the number of simultaneous students in an exam multiplied by the size of the data they are accessing. For example, 200 students viewing a page with a 5Mb PDF file will generate 1Gb of network traffic. If this is going into one computer lab then if might be necessary to investigate the speed rating of the switches and other gear which serves that lab. A way to partly mitigate against large spikes is to include larger files within the middle of an exam so that not all the students will be requesting the file at the same time as they work through the exam at their own rates.
Storage - the Rogo application Rogō application has quite modest storage needs, the main requirement will be the amount of media uploaded with each question. Images are usually not too large but attached PDF files, audio and video formats can take up quite a bit of space.

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title	File System Permissions

Most directories in Rogō should be set up to be writable by the owner only:

drwxr-xr-x

Exceptions to this rule include the following directories which need to allow higher write privilagesprivileges:

`<rogo-dir>/help/staff/images`
`<rogo-dir>/help/student/images`
`<rogo-dir>/media`
`<rogo-dir>/email_templates`
`<rogo-dir>/qti/imports`
`<rogo-dir>/qti/exports`
`<rogo-dir>/config` - for installation only, so that config.inc.php can be written. This should be changed back to being writeable writable by the owner only after installation.
`<rogo-dir>/users/photos`
`/tmp`

For these writable directories the permissions should be set to drwxrwxr-x for the user that Apache runs as.

Note:
The path to the temporary directory (e.g. /tmp) is configurable in /config/config.inc.php.

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title	Apache Settings

Optimising apache can be a specialised task so if you have an apache expert/expereinced experienced sysadmin please consult with them.

Server prefork settings

The settings for apache adjust how many processess processes are listening and how many spare threads are available (As of writing this document running php as a module in apache is only recommended for the prefork configuration of apache). For small scale tests then the default apache settings are acceptable, but to increase performance then the numbers should be increased (this will usually use more ram as these are extra processessprocesses). It is recommended to increase the minumum minimum spare servers & the start servers (as this will improve the initial start from when the users arrive at the page as it can cope with more simultaneous requests) This is directly related to how much RAM is used

For more info about this please go and read the Apache documentation.

Server prefork settings from a basic apache config from a default install of apache in Centos 6.2

Code Block

language	bash

StartServers       8
MinSpareServers    5
MaxSpareServers   20
ServerLimit      256
MaxClients       256
MaxRequestsPerChild  4000

An example from a university of Nottingham Apache config for prefork settings

Code Block

language	bash

StartServers         50
MaxClients          150
MinSpareThreads      25
MaxSpareThreads      75 
ThreadsPerChild      25
MaxRequestsPerChild   0

Security related configuration

As a minimum Apache should be configured with the following to prevent access to sensitive files

Code Block

language	bash

# The following lines prevent .htaccess and .htpasswd files from being
# viewed by Web clients.
<FilesMatch "^\.ht">
    Order allow,deny
    Deny from all
    Satisfy All
</FilesMatch>

#The following lines prevent .inc files files from being
# viewed by Web clients.
<FilesMatch "\.inc$">
    Order allow,deny
    Deny from all
    Satisfy All
</FilesMatch>

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title	PHP Settings

Below are some of the settings which may need to be altered from their default values:

Code Block

language	bash

max_execution_time = 120
memory_limit = 512M
post_max_size = 20M
upload_max_filesize = 20M
default_charset = "utf-8"
mbstring.internal_encoding = UTF-8
max_input_vars = 3000

E-mail configuration

Rogo Rogō uses the built in PHP mail functions to send e-mail, therefor you will need to configure it correctly for your environment.

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Rogō main configuration file is in /config/config.inc.php – This holds system wide setting for your installation.

Known Issues

Rogo uses Rogō uses a large number of prepared SQL statements, MySQL before version 5.1 does not cache prepared statements. Using MySQL version grater greater than 5.1 is highly recommended for large cohorts.

DO NOT USE Apache Alias for the rogo directory Rogō directory as this will break things, it looks like a subdirectory sub-directory installation but doesnt does not work as the apache Apache document root is not related to the path of the php files.

Versions Compared

Old Version 19

New Version 20

Key

E-mail configuration

Known Issues