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Swap which option is better

 
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Top Forums UNIX for Dummies Questions & Answers Swap which option is better
# 8  
Old 09-01-2011
Quote:
Originally Posted by Tommyk
although i personally have never tested it, i have been told swap partitions work better than swap files.
Again, the benefit happens when swap is on a different disk, not just a different partition..
# 9  
Old 09-01-2011
https://lkml.org/lkml/2005/7/7/326

See andrew Morton's comment on question 2.
Quote:
> 2. Is it possible for the swapfile to become fragmented over time, or
> does it just keep using the same blocks over and over? i.e. if it's
> all contiguous when you first create the swapfile, will it stay that
> way for the life of the file?

The latter. Create the swapfile when the filesystem is young and empty,
it'll be nice and contiguous. Once created the kernel will never add or
remove blocks. The kernel won't let you use a sparse file for a swapfile.
Just food for thought Smilie
# 10  
Old 09-01-2011
Large files created whole by dd ought to be contiguous anyway. I continue to consider it a nonissue -- especially when there's already much bigger problems caused by having it on the same disk at all.
# 11  
Old 09-01-2011
Quote:
Originally Posted by Corona688
Large files created whole by dd ought to be contiguous anyway.
I agree, when You have fresh filesystem...
But what when it's physicaly impossible? Eg. sda1 was up to 99% used, then You moved/deleted some files, and then You create Your swapfile on that sda1.
In this case file could be spread over whole disk. And this will have an influence on efficiency. Ain't I right?
But with swap partition You are _sure_ that all swap is really continuous, in one place.
That's how I see this Smilie Please tell me if I'm wrong.
# 12  
Old 09-01-2011
Quote:
Originally Posted by sulti
I agree, when You have fresh filesystem...
But what when it's physicaly impossible? Eg. sda1 was up to 99% used, then You moved/deleted some files, and then You create Your swapfile on that sda1.
In this case file could be spread over whole disk. And this will have an influence on efficiency. Ain't I right?
Swap is random-access by definition. Using it will thrash your disk like a wounded moth no matter how contiguous your swapfile is, fragmentation can't really make that worse. The overhead is simply the usual overhead of using a file at all.

While it's busy thrashing like that, a disk has a difficult time doing anything else, which is the real problem in putting your swap on the same drive as your files.
 
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