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I am changing my hard disk to ext3 because journalling got so much write my server crash.

Well, now I use SSD. Journalling is no longer the issue.

But SSD are small.

Will journaling takes so much space?

kjournald writes 5MB-10MB of data all the time. However, there is no file that's bigger than 2MB.

So I wonder what it actually writes.

We don't have this in windows right?

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Most modern file systems use a journal or a similar approach and NTFS does it, too. – scai Jan 8 '13 at 8:26
"We don't have this in windows right?" Sure? Most things "in Windows" seem rather opaque, I couldn't tell how its journaling works from poking around... – sr_ Jan 8 '13 at 8:47
What daemon are you running on your server ? Anything that uses a lot of Disk I/O ?? Perhaps you can install a utility called iotop and see what process is performing the most I/O. – Garfield Carneiro Jan 8 '13 at 15:31
I did. That process is called kjournald. It seems that kjournald writes way more data than real writes. – Jim Thio Jan 9 '13 at 0:33
Have you apply noatime to fstab yet? – John Siu Jan 9 '13 at 4:33
up vote 3 down vote accepted

A filesystem journal (which you are seeing as 5MB-10MB) is a collection of all pending changes to the filesystem and not necessarily belonging to one file.

The Journal is more like a rough changes that are pending to be written to hard disk. By using a buffer before actual write we have an advantage to keep filesystem consistent incase of power failure or system crash but the disadvantage is every changes to filesystem are written twice (once to the journal and second time in HardDisk )

This space is internally used by filesystem and more likely to be stored in OS memory or a fixed area instead as a file on a filesystem.

Windows NTFS does have journaling inbuilt into it

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But the number of writes are not even that much. Nothing else writes too much. – Jim Thio Jan 8 '13 at 13:11

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