Ce contenu n'est pas disponible dans la langue sélectionnée.
5.7. Storage Management Day-to-Day
System administrators must pay attention to storage in the course of their day-to-day routine. There are various issues that should be kept in mind:
- Monitoring free space
- Disk quota issues
- File-related issues
- Directory-related issues
- Backup-related issues
- Performance-related issues
- Adding/removing storage
The following sections discuss each of these issues in more detail.
5.7.1. Monitoring Free Space
Making sure there is sufficient free space available should be at the top of every system administrator's daily task list. The reason why regular, frequent free space checking is so important is because free space is so dynamic; there can be more than enough space one moment, and almost none the next.
In general, there are three reasons for insufficient free space:
- Excessive usage by a user
- Excessive usage by an application
- Normal growth in usage
These reasons are explored in more detail in the following sections.
5.7.1.1. Excessive Usage by a User
Different people have different levels of neatness. Some people would be horrified to see a speck of dust on a table, while others would not think twice about having a collection of last year's pizza boxes stacked by the sofa. It is the same with storage:
- Some people are very frugal in their storage usage and never leave any unneeded files hanging around.
- Some people never seem to find the time to get rid of files that are no longer needed.
Many times where a user is responsible for using large amounts of storage, it is the second type of person that is found to be responsible.
5.7.1.1.1. Handling a User's Excessive Usage
This is one area in which a system administrator needs to summon all the diplomacy and social skills they can muster. Quite often discussions over disk space become emotional, as people view enforcement of disk usage restrictions as making their job more difficult (or impossible), that the restrictions are unreasonably small, or that they just do not have the time to clean up their files.
The best system administrators take many factors into account in such a situation. Are the restrictions equitable and reasonable for the type of work being done by this person? Does the person seem to be using their disk space appropriately? Can you help the person reduce their disk usage in some way (by creating a backup CD-ROM of all emails over one year old, for example)? Your job during the conversation is to attempt to discover if this is, in fact, the case while making sure that someone that has no real need for that much storage cleans up their act.
In any case, the thing to do is to keep the conversation on a professional, factual level. Try to address the user's issues in a polite manner ("I understand you are very busy, but everyone else in your department has the same responsibility to not waste storage, and their average utilization is less than half of yours.") while moving the conversation toward the matter at hand. Be sure to offer assistance if a lack of knowledge/experience seems to be the problem.
Approaching the situation in a sensitive but firm manner is often better than using your authority as system administrator to force a certain outcome. For example, you might find that sometimes a compromise between you and the user is necessary. This compromise can take one of three forms:
- Provide temporary space
- Make archival backups
- Give up
You might find that the user can reduce their usage if they have some amount of temporary space that they can use without restriction. People that often take advantage of this situation find that it allows them to work without worrying about space until they get to a logical stopping point, at which time they can perform some housekeeping, and determine what files in temporary storage are really needed or not.
Warning
If you offer this situation to a user, do not fall into the trap of allowing this temporary space to become permanent space. Make it very clear that the space being offered is temporary, and that no guarantees can be made as to data retention; no backups of any data in temporary space are ever made.
In fact, many administrators often underscore this fact by automatically deleting any files in temporary storage that are older than a certain age (a week, for example).
Other times, the user may have many files that are so obviously old that it is unlikely continuous access to them is needed. Make sure you determine that this is, in fact, the case. Sometimes individual users are responsible for maintaining an archive of old data; in these instances, you should make a point of assisting them in that task by providing multiple backups that are treated no differently from your data center's archival backups.
However, there are times when the data is of dubious value. In these instances you might find it best to offer to make a special backup for them. You then back up the old data, and give the user the backup media, explaining that they are responsible for its safekeeping, and if they ever need access to any of the data, to ask you (or your organization's operations staff -- whatever is appropriate for your organization) to restore it.
There are a few things to keep in mind so that this does not backfire on you. First and foremost is to not include files that are likely to need restoring; do not select files that are too new. Next, make sure that you are able to perform a restoration if one ever is requested. This means that the backup media should be of a type that you are reasonably sure will be used in your data center for the foreseeable future.
Note
Your choice of backup media should also take into consideration those technologies that can enable the user to handle data restoration themselves. For example, even though backing up several gigabytes onto CD-R media is more work than issuing a single command and spinning it off to a 20GB tape cartridge, consider that the user can then be able to access the data on CD-R whenever they want -- without ever involving you.
5.7.1.2. Excessive Usage by an Application
Sometimes an application is responsible for excessive usage. The reasons for this can vary, but can include:
- Enhancements in the application's functionality require more storage
- An increase in the number of users using the application
- The application fails to clean up after itself, leaving no-longer-needed temporary files on disk
- The application is broken, and the bug is causing it to use more storage than it should
Your task is to determine which of the reasons from this list apply to your situation. Being aware of the status of the applications used in your data center should help you eliminate several of these reasons, as should your awareness of your users' processing habits. What remains to be done is often a bit of detective work into where the storage has gone. This should narrow down the field substantially.
At this point you must then take the appropriate steps, be it the addition of storage to support an increasingly-popular application, contacting the application's developers to discuss its file handling characteristics, or writing scripts to clean up after the application.
5.7.1.3. Normal Growth in Usage
Most organizations experience some level of growth over the long term. Because of this, it is normal to expect storage utilization to increase at a similar pace. In nearly all circumstances, ongoing monitoring can reveal the average rate of storage utilization at your organization; this rate can then be used to determine the time at which additional storage should be procured before your free space actually runs out.
If you are in the position of unexpectedly running out of free space due to normal growth, you have not been doing your job.
However, sometimes large additional demands on your systems' storage can come up unexpectedly. Your organization may have merged with another, necessitating rapid changes in the IT infrastructure (and therefore, storage). A new high-priority project may have literally sprung up overnight. Changes to an existing application may have resulted in greatly increased storage needs.
No matter what the reason, there are times when you will be taken by surprise. To plan for these instances, try to configure your storage architecture for maximum flexibility. Keeping spare storage on-hand (if possible) can alleviate the impact of such unplanned events.
