[Novalug] Hard drive saturation

John Franklin franklin@elfie.org
Sat Jul 9 18:47:04 EDT 2011


On Jul 9, 2011, at 4:12 PM, Roy Wilson wrote:
[snip "When drive is >80% full, performance tanks."]

>  Is there a problem like that with linux?  I'm running the latest Kubuntu on 
> the machine with that drive.

It's a problem with every file system I know of.  Some handle it better than others, but the crux of the problem is the filesystem has to fragment files more as the disk fills up.  As more data is written to the disk, the areas of free contiguous blocks get smaller and farther apart, requiring more seeks which reduces performance.

File systems that try to coalesce free space, like Log File System, don't fare any better.  In fact, they can be worse because above 80% they're working furiously to free up space for the next write.

What can you do to improve things?  You can make sure the machine and RAID controller have lots of cache and use LVM / resize2fs to expand the volume.  That's about all you've got.

jf
-- 
John Franklin
franklin@elfie.org
ICBM: 39º 01' 58.4"N 77º 24' 49.6"W Z+84m

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