HOWTO: Multi Disk System Tuning: Concluding Remarks

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## 18. Concluding Remarks

Disk tuning and partition decisions are difficult to make, and there are no hard rules here. Nevertheless it is a good idea to work more on this as the payoffs can be considerable. Maximizing usage on one drive only while the others are idle is unlikely to be optimal, watch the drive light, they are not there just for decoration. For a properly set up system the lights should look like Christmas in a disco. Linux offers software RAID but also support for some hardware base SCSI RAID controllers. Check what is available. As your system and experiences evolve you are likely to repartition and you might look on this document again. Additions are always welcome.

Finally I'd like to sum up my recommendations:

- Disks are cheap but the data they contain could be much more valuable, use and test your backup system.
- Work is also expensive, make sure you get large enough disks as refitting new or repartitioning old disks takes time.
- Think reliability, replace old disks before they fail.
- Keep a paper copy of your setup, having it all on disk when the machine is down will not help you much.
- Start out with a simple design with a minimum of fancy technology and rather fit it in later. In general adding is easier than replacing, be it disks, technology or other features.

## 18.1 Coming Soon

There are a few more important things that are about to appear here. In particular I will add more example tables as I am about to set up two fairly large and general systems, one at work and one at home. These should give some general feeling on how a system can be set up for either of these two purposes. Examples of smooth running existing systems are also welcome.

There is also a fair bit of work left to do on the various kinds of file systems and utilities.

There will be a big addition on drive technologies coming soon as well as a more in depth description on using `fdisk`, `cfdisk` and `sfdisk`. The file systems will be beefed up as more features become available as well as more on RAID and what directories can benefit from what RAID level.

There is some minor overlapping with the Linux Filesystem Structure Standard and FHS that I hope to integrate better soon, which will probably mean a big reworking of all the tables at the end of this document.

As more people start reading this I should get some more comments and feedback. I am also thinking of making a program that can automate a fair bit of this decision making process and although it is unlikely to be optimum it should provide a simpler, more complete starting point.

## 18.2 Request for Information

It has taken a fair bit of time to write this document and although most pieces are beginning to come together there are still some information needed before we are out of the beta stage.

- More information on swap sizing policies is needed as well as information on the largest swap size possible under the various kernel versions.
- How common is drive or file system corruption? So far I have only heard of problems caused by flaky hardware.
- References to speed and drives is needed.
- Are any other Linux compatible RAID controllers available?
- What relevant monitoring, management and maintenance tools are available?
- General references to information sources are needed, perhaps this should be a separate document?
- Usage of `/tmp` and `/var/tmp` has been hard to determine, in fact what programs use which directory is not well defined and more information here is required. Still, it seems at least clear that these should reside on different physical drives in order to increase paralellicity.

## 18.3 Suggested Project Work

Now and then people post on comp.os.linux.*, looking for good project ideas. Here I will list a few that comes to mind that are relevant to this document. Plans about big projects such as new file systems should still be posted in order to either find co-workers or see if someone is already working on it.

Planning tools

  that can automate the design process outlines earlier would probably make a medium sized project, perhaps as an exercise in constraint based programming.

Partitioning tools

  that take the output of the previously mentioned program and format drives in parallel and apply the appropriate symbolic links to the directory structure. It would probably be best if this were integrated in existing system installation software. The drive partitioning setup used in Solaris is an example of what it can look like.

Surveillance tools

  that keep an eye on the partition sizes and warn before a partition overflows.

Migration tools

  that safely lets you move old structures to new (for instance RAID) systems. This could probably be done as a shell script controlling a back up program and would be rather simple. Still, be sure it is safe and that the changes can be undone.

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