Defrag Single File Linux ext3

[lambchops511]

Sorry if wrong section.

I have a relatively (50G) large file on ext3, I need good linear access / bandwidth times on it. Is there a way to "defrag", the way it was copied over to the server I am pretty sure was fragmented pretty badly. I don't need perfect defrag, but is there a good way to make the file "less fragmented"?

Would a something simple like

cp my_file /tmp/garbage
rm my_file
mv /tmp/garbage my_file

do the magic?

 

[Cerb]

Tried defrag?

There's also shake, which is probably better.

Also, yeah, this should probably go under *nix Software.

 

[AnonymouseUser]

To see how fragmented a file is, use

filefrag -v filename

 

[mfenn]

To see how fragmented a file is, use

filefrag -v filename

:thumbsup: Let's not get crazy unless there is actually a problem. I wouldn't be worried unless the file had thousands of extents.

 

[lambchops511]

To see how fragmented a file is, use

filefrag -v filename

WOW! THANKS! I did not know this command. Is 86 extents good / bad for a 30 G file? I am guessing its pretty good? That probably means if I want better IO perf I need to hit SSDs?

 

[Cerb]

WOW! THANKS! I did not know this command. Is 86 extents good / bad for a 30 G file? I am guessing its pretty good? That probably means if I want better IO perf I need to hit SSDs?

Yes. Generally, anything above around 50MB/fragment is, "good enough," and that's over 300MB/fragment. Even with some tiny fragments mixed in there, that's good enough to just not worry about it. Any newish HDD (500GB/platter or denser) aught to be able to read such a file at 100MB/s, no sweat.

 

[mfenn]

Yes. Generally, anything above around 50MB/fragment is, "good enough," and that's over 300MB/fragment. Even with some tiny fragments mixed in there, that's good enough to just not worry about it. Any newish HDD (500GB/platter or denser) aught to be able to read such a file at 100MB/s, no sweat.

Agree.

OP, the -v output from filefrag lists all the file's extents along with their length (5th column). Double-check to make sure that there aren't a bunch of really tiny extents, but you are most likely OK.