What is the difference between ext3 & ext4 from a generic user's perspective

Question

What are the big differences between ext3 and ext4 from a generic user's perspective? I heard that sticking with ext3 is wiser. Is that true?

EDIT: One thing I want to note is that I am a dual OS user (Windows & Ubuntu), so not being able to mount a drive (ext4) from Windows is a big negative for me. But, ext3 has this privilege.

Solution 1

A few years ago I'd say stick with ext3 but nowadays ext4 is better. A recent (May 16, 2011) round up from thegeekstuff.com sums it up rather nicely:

• Supports huge individual file size and overall file system size.
• Maximum individual file size can be from 16 GB to 16 TB
• Overall maximum ext4 file system size is 1 EB (exabyte). 1 EB = 1024 PB (petabyte). 1 PB = 1024 TB (terabyte).
• A directory can contain a maximum of 64,000 subdirectories (as opposed to 32,000 in ext3)
• You can also mount an existing ext3 fs as ext4 fs (without having to upgrade it).
• Several other new features are introduced in ext4: multiblock allocation, delayed allocation, journal checksum, fast fsck, etc. All you need to know is that these new features have improved the performance and reliability of the filesystem when compared to ext3.
• In ext4, you also have the option of turning the journaling feature off.

A very good comparison from 2009 on linuxologist.com has a graph about write performance with 4 GB:

and also has some other information on ext4.

I myself have had zero problems with ext4.

If you need to share a partition with Windows you will need ext3. I myself have given up on Windows so I have everything set to ext4 and use a USB stick to transfer data to a Windows machine (mainly at work).

What you can do for a setup is the following:

/ ext4
swap
/home  ext4
/datapartiton_with_windows ext3

Then you can make the last one a shared partition for both OS's.

Solution 2

The only reasons I can think of at the current time not to use ext4 are compatibility with older systems, and, last time I tried it, ext4 had problems with losing data when used on flash media (ie. Thumb drives et cetra.) That second one I haven't tested in about six months, so it may have been fixed. Otherwise, the performance and reliability are large improvements over ext3.

Edit: Ten years later, the data corruption on cheap USB flash devices has most certainly been fixed and some distros aren't bothering to enable ext3 drivers by default.

Comments

[Rinzwind]

True. I tend to use a USB stick for that. Copy to stick and data is available on other OS'es.

[CR2]

nowadays it is possible to read ext4 in Windows. Use the utility called ext2read. so is there any other problem left with ext4 FS/

[fqdn]

That "loosing data" problem, unless it's been fixed, has nothing to do with unsafely removing the medium and everything to do with ext4 taking some assumptions about how the storage device works that aren't true with cheap flash drives. You don't have to remove the medium at all. Just do a big pile of data transfers like, say, installing linux to an ext4 flashdrive. Last time I tried it you'd start getting corrupted and missing files almost before the installation was complete. And no, there was nothing physically wrong with the drive. It worked fine with ext3.

[vaquito]

Journalling is generally a good thing. Only turn it off if you know exactly what you are doing.

[Rich M]

You can see EXT4 shares in Windows, I'm looking at one right now. (Windows 10 1809 and QTS 4.3.6) I know they can also been seen under Windows 7.

[Rinzwind]

Nope. You are looking at a samba share. Not directly on ext4.

[Rich M]

But I can still see the data in Windows so I don't need EXT3 is my point.

[Rich M]

You've said "If you need to share a partition with Windows you will need ext3". I can see the data stored on my shared EXT4 partition in Windows so the mechanics don't really matter in this instance. I don't need EXT3 to view my data is my point.

[qrtLs]

not sure to generalize that. every fs may lose data if usb if removed unsafely, ext4 at least notices, ext3 just goes silent about it afaik

[fqdn]

@qrtLs Depends on what options you have set. ext3 and ext4 are both configurable about how aggressively they try to avoid losing data vs maximizing performance. The corruption issue at the time I think was caused by the driver assuming the device was telling the truth when it reported certain metadata writes were complete, and then copying those sectors to elsewhere, leading to incorrect data being pushed around. So far as I know it has been fixed.