A quick and easy performance improvement

Phillip Udel Phil.Udel at salemcorp.com
Wed Jul 26 20:05:59 IST 2006

IMO.  If you are running a raid system like I do. File placement has even
less value. I used to separate almost all my main dir's but back in the 80's
lol but now I am less concerned. Now if your running HPUX :) my favorite
Unix OS  you could control how a IO went down to the arm by file, but modern
OS's depend more on cache to replace placement. 

-----Original Message-----
From: mailscanner-bounces at lists.mailscanner.info
[mailto:mailscanner-bounces at lists.mailscanner.info] On Behalf Of Mike
Sent: Wednesday, July 26, 2006 1:48 PM
To: MailScanner discussion
Subject: Re: A quick and easy performance improvement

Julian Field wrote:
> I have found in the past that splitting the installation into many 
> different partitions just causes more problems than it solves. Putting 
> /var separate on Solaris is a classic example. People say "when your 
> logs get big it won't fill /" which is true enough. But disks are huge 
> and cheap these days. Why not just do it properly and roll your logs 
> properly so they never occupy a lot of space? If you have them 
> separate, then as you install more patches, /var/sadm will start to 
> get very large, which there is nothing you can do about, so after 2 or 
> 3 years your /var will fill and you'll have to start bodging things to 
> get them out of /var to give you more room for /var/sadm.
> I just find it causes more problems than it solves, so long as you set 
> up your system to maintain itself properly. If you never roll 
> /var/log/maillog on a MailScanner system then yes, it will get very 
> large, but set it up properly and keep your logs and quarantines pruned.

I don't think thats very true. Most systems that are setup with a single 
/ partition are done so by the clueless. Separating your partitions 
gives you a number of advantage including protection from disk space 
starvation, and increased performance when they are strategically laid out.

Hard drives can transfer data much more quickly from outer tracks than 
they can from inner tracks.  To take advantage of this you should try to 
pack your smaller file systems and swap closer to the outer tracks, 
follow with the larger file systems,  and end with the largest file systems.

Separate partitions also allow different mount options, and in the event 
of data loss due to power outages, etc, it is more likely that the 
system will still come up, making it easier for you to restore from 
backup as necessary.

Finally some operating system such as FreeBSD automatically optimize the 
layout of files on a file system, depending on how the file system is 
being used. So a file system that contains many small files that are 
written frequently will have a different optimization to one that 
contains fewer, larger files. By having one big file system this 
optimization breaks down.

Of course one should always size the partitions according to requirements.

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