Information Technology HELPDESK

Best Practises for Using the UEL Network

Disk Storage - Email

DISK STORAGE

Disk Quotas

There are obviously physical limits to the amount of disk space available on the University’s servers and there are limits to how much extra disk space can be added to a server before a newer server is required. There are two main functions that the Network Administrators have to consider when allocating disk space to users:
  1. To provide what ever disk storage space is required to support the business of the University.
  2. To ensure that the University’s IT resources are used appropriately.
To ensure appropriate use, and thus preserve resources for legitimate use, quotas are set on how much disk space a user can take up with their files and email.

A default quota of 100Mb is therefore set for all users on their home servers (this quota includes both H: and I: drives) and 50Mb for email. If you have a legitimate business reason for requiring more disk, or email, space, please contact the Network Team on ext 6661, or you can email ‘Network Admin’.

Best Practise for Disk Space Usage

For University staff who always use the same computer, there is typically much more disk space available on the local disk drive(s) C: and/or D: than will be available on their network area. However, you need to be aware that files on your local disk drives will not be backed up unless you yourself take a copy on another disk or other local device (e.g. CD, floppy disk etc). Working directly on your local disk drives is not advised as you will lose everything in the event of hardware failure or theft of your PC.

The best way to combine the use of network and local storage is to keep files you are currently working on, on your network area so that we can take a backup copy of them (this happens overnight on each weekday). If you are short of disk space on your network area, I would suggest that any files that have not been modified for more than one month be moved to your local disk drive (On the last Friday of each month we take a backup that is kept for one year. It is therefore essential that files are kept on the network until after at least one month end back up has been taken. Backups taken at other times are kept for shorter periods). This method of working has 3 advantages:

  1. Network resources are freed up for reuse by both yourself and other users.
  2. Older files are still available on demand (You obviously need to ensure that files on your local disk drives are copied/preserved during any PC replacement/upgrades).
  3. A backup copy is kept on tape for emergencies. (Please be aware that restoring files from backup can take several hours and is therefore a service that is strictly for emergencies!)

EMAIL

Mail Addressing and Routing

The main UEL mail system is the Exchange system which is usually accessed using the Outlook mail client. Outlook and Exchange work closely with the Windows Active Directory Service and will route mail directly to the correct mailbox as long as local mail addresses are used. If the sender uses the same mail server as the recipient(s) the message will be delivered without having to travel outside of that mail server. Local addresses are used whenever you use the Outlook address book, or simply type someones real name (or their login name which should change to display their real name). A valid local address will change to bold underlined text after a few seconds.

Mail which is addressed to someone@uel.ac.uk will be treated as external mail. It will leave the Exchange system and pass to the UEL external mail gateway machines before being redirected back into the Exchange system and, in most cases, ending up back on the same server it began its journey from. This is obviously a very inefficient way to travel if the recipient(s) are using the same mail server as the sender.

The Outlook address book can be accessed via the icon on the main menu bar, or using the 'To:' button when composing a message.

Single Instance Storage

The Exchange mail system used at UEL keeps only a single instance of any single item for each mail store. I.e. a message sent to 20 people whose mailboxes are located in the same mail store will generate just a single copy of that message – with links to 20 mailboxes. As each person deletes that message, the link to their mailbox is removed. Only when the 20th person deletes the message is it truly removed from the mail store.

When sending a message to several people it is therefore more efficient to send it simultaneously to all intended recipients, rather than sending to a few and then forwarding to a few more (which would generate additional copies every time you click the send button).

One disadvantage of the single instance storage is that it only takes one recipient to keep a copy of any message for that message to be retained by the system. If a message has been sent to a very large number of people then it is likely that that message will never be deleted from the system. Therefore it is more efficient to place messages intended for a large number of recipients into a public folder (see below).

The UEL Exchange system has been configured to prevent sending to more than 4000 recipients at a time (this is the maximum group size on the system). Users who cause annoyance to others by sending blanket emails to all users may have their recipient limits reduced to prevent them repeating this behaviour.

Public Folders

The Exchange mail system includes a feature known as public folders. Public folders are not associated with any single mailbox/user and are intended for items that will be read by a large number of people. As each item will only be kept in that folder with no links elsewhere, public folders are a very efficient storage method and items that are no longer required are easily located and deleted.

Message Size

Email systems were originally designed for simple text messages. In recent years mail browsers have become much more sophisticated and can now handle a wide range of messages formats and file attachments. However, the mail transport systems (i.e. the bits that connect different mail systems) have not kept pace with this development and can be quite slow when dealing with large messages. This is at least partly because they have to follow rigid standards in order to ensure that they can talk to many other different mail systems (which may be running on different operating systems).

The Exchange system at UEL is quite efficient at handling different mail formats, but is less efficient at handling large messages. This is because every message is first written to transaction logs which are a fixed 5Mb size. Large messages may therefore be spread across more than one transaction log. The more recipients with mailboxes in different mail stores, the more transaction logs will be involved and the less efficiently the system handles the task.

UEL mail systems have been configured to reject any messages larger than 5Mb.

This also offers some protection from a nasty trick known as mail bombing. This is where some malicious person deliberately sends large messages with the intention of filling up a recipient’s mailbox until it stops accepting messages.