News Group Posts

file system layout

There are a few basic reasons to have separate filesystems:

However, IMNSHO, there is damn little reason for this anymore, and I regularly and usually don't bother with separate fs's unless I have something specific in mind like /var/spool/tmp or some giant database.

However, one or more of these reasons may still apply:

• There isn't space on the hard drive to fit everything you need. This, of course, was very common in the days of small hard drives, but seldom is an issue nowadays.
  
  
• Related to that is the situation where you WANT the data on a separate drive for other reasons, but that forces a separate fs so it isn't a "reason", it's a requirement.
  
  
• You want to control how much data gets put on a drive. For example, in some environments, I'll make /var/spool/lp/temp a small fs of its own. This causes it to fill up if there are too many unfulfilled print jobs, which calls attention to the problem before it really gets out of hand and fills up something more important. The idea here is that it's better not to print than not to work at all.
  
  
• You can't fit an entire drive on your backup media, and want to keep volatile data on separate fs's to make it easier to use archaic backup programs like "dump". This is unlikely to be a problem nowadays except for the very largest systems.
  
  
• You want to be able to do upgrades or reinstalls and leave some fs's untouched. This remains a valid reason for separating certain areas from others, but with the speed and capacity of modern backup systems, it is hardly as compelling as it used to be.
  
  
• You want to be able to clean the fs in the event of a crash. Older large fs's, took a long time to clean and fsck needed more memory than was likely to be present, so it would need scratch files, which slowed it down further. It was not at all unusual for these fs's to get confused for no particular reason; not from a crash, just because, so it was obviously better to clean one or two small fs's now and then as opposed to having to clean one big fs every time this happened. Linux fs's still have that mentaility, btw, and will automatically run fsck after x number of boots and/or x number of days. Older Sun fs's would run it on EVERY boot. Modern fs's very seldom need to run fsck anyway, so this is not an issue. I imagine it won't be an issue for Linux, either, once it catches up in this area.
  
  
• You want to contain the damage. On older systems, it was often observed that if you had physical or electronic damage, it was sometimes unrecoverable by fsck, but that it was very apt to be confined to one fs. Therefore, spreading the fs's out made it more likely that more of your data survived a crash. Again, this is unlikely to be an issue with modern fs's, and as we tend to back up more data more often from and to more reliable media, it's even less important.
  
  

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