Is Ext4 a safe bet now?

Dark Foo · l33t Joined: 21 Nov 2008 Posts: 901 Location: 127.0.0.1

Or is it still an idea to use ext3 for a bit longer, i have managed to get some bits and pieces together and am about to install gentoo on it, so am working out what to use
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mv · Advocate Joined: 20 Apr 2005 Posts: 2483

If you plan to access to disks only with kernel-2.6.30 or newer: use ext4.

gerard82 · Posted: Sun Jan 24, 2010 4:41 pm Post subject:

I've switched to ext4 ~1 year ago on my desktop.
Contrary to all the scary stories I haven' lost anything sofar.
Had a power outage abt a month ago,nothing lost.
And fsck is soooo fast!
I regularly make backups but did that on ext3 also.
Gerard.
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Dark Foo · l33t Joined: 21 Nov 2008 Posts: 901 Location: 127.0.0.1

yes i will have back ups so i should be ok, thanks :-)

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uaeb · n00b Joined: 28 May 2008 Posts: 27

Well Google has announced that it's switching from ext2 to ext4 recently. But if your concerned about performance, you may want to give it a miss for a little bit longer: http://www.phoronix.com/scan.php?page=article&item=ext4_then_now&num=1

d2_racing · Posted: Sun Jan 24, 2010 9:00 pm Post subject:

And for the migration thing, you can backup your partition with a Stage 4 or Stage 5, format it and then restore your tar.

It's clean and simple

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cach0rr0 · Posted: Sun Jan 24, 2010 10:18 pm Post subject:

I've had no problems whatsoever with ext4 as my root fs, though, this is a laptop so I'm never going to experience the immediate power loss (it shuts itself down gracefully if battery is too low)

if you do go ext4, i would steer clear of 2.6.33 until we can make some sense of Phoronix' claims that ext4 has suffered a huge performance regression in 2.6.33

This isn't the fastest FS I've ever dealt with, but it's pretty damn stable, and "good enough" for my day to day use.
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CaptainHero · n00b Joined: 27 Nov 2009 Posts: 41 Location: Germany

The only issue I had with an ext4 root partition was that like every 2 or 3 boots fsck told me there was data inconsistency and it had to be repaired.

The reason probably was that it wasn't properly unmounted when shutting my PC down. I got the hint to mount it with the option "journal_checksum", since then fsck never spoke to me again.

kernelOfTruth · Posted: Sun Jan 24, 2010 10:38 pm Post subject:

Shining Arcanine · Veteran Joined: 24 Sep 2009 Posts: 1110

I have been running ext4 on my laptop and in virtual machines and I have not had a single issue with data corruption on it. It is as stable as a rock.

However, there is one minor issue. Ext4 performance has been dropping in newer kernel versions as the kernel developers have been prioritizing data integrity above performance:

http://www.phoronix.com/scan.php?page=article&item=linux_perf_regressions&num=1

Supposedly, this can be fixed by mount with nobarrier, as the commit in 2.6.32 that caused this issue turned barrier=1 on by default. However, it is my understanding that additional performance losses are in 2.6.33 and it is not known to me whether or not the commits that caused these can be disabled with the nobarrier mount flag:

http://www.phoronix.com/scan.php?page=article&item=ext4_then_now&num=1

From what I have read, the commit in 2.6.33, affects ext3 as well as ext4 because it makes barrier=1 the default mount option for both file systems, however, since the commit, ext3 performance has been higher than ext4 performance (with default mount options):

http://www.phoronix.com/scan.php?page=article&item=linux_2632_fs&num=1

nobarrier is not a recommended mount option unless either your system is battery-backed up or your drive has a way of flushing its cache in the event of a power failure. I have heard of some SSDs have capacitors that enable them to do this. Off the top of my head, the issue with nobarrier is that it allows changes to be made to a disk before they are logged to the journal so in the event of a power outage, the journal will not accurately reflect what has been written to the disk, which can cause data integrity issues, although someone might have to correct me on that, as I do not remember where I read that to be able to verify my memory and cite my source.

I am not trying to scare you away from ext4, but these are some things to keep in mind. Perhaps some other people here could add more information, such as whether or not the commits in 2.6.33 that negative affect ext4 performance are disabled by the nobarrier mount option, which is something I am eager to learn myself.

kernelOfTruth · Posted: Mon Jan 25, 2010 1:30 am Post subject:

mv · Advocate Joined: 20 Apr 2005 Posts: 2483

kernelOfTruth · Posted: Mon Jan 25, 2010 2:54 pm Post subject:

Dark Foo · l33t Joined: 21 Nov 2008 Posts: 901 Location: 127.0.0.1

well laptop would be first to have the make over, then the little box i managed to get together both only really play films or me surfing net and looking at email, films are backed up on disc (blu-ray takes a lot of space - mkv doesn't

) and email is imap, so i should lose anything i cant replace.

As to the kernel what is the default one that ships atm, i can always pull an older one from portage if i need to
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mv · Advocate Joined: 20 Apr 2005 Posts: 2483

Dark Foo · l33t Joined: 21 Nov 2008 Posts: 901 Location: 127.0.0.1

so basically, do it as i always have, no special mount options required? :-)

Main system (this one might be different) that has a bit of a heavier disk usage, will cross that bridge when i come to it, speed it not that important to me, making sure my data is there is :-)

edit: dual booting win7 and linux bites now as i have to use extended partitions ;-/
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Cyker · Veteran Joined: 15 Jun 2006 Posts: 1427

I'm still using ext4 in backward-compatibility mode so that I can use the ext3 or even ext2 filesystem driver to access the partitions if I need to.

The main one is to just mount it with the noextents option (Although be careful: This switch is broken on newer kernels; They assume that because the default is noextents the switch is useless which is dangerous and shortsighted. I'm now slightly terrified that if I ever have to mount an older kernel I will hose my main filesystem because older kernels NEED that switch otherwise they can, under certain circumstances, convert your FS without even asking you!)

The barriers thing is just awful; There must be a better way! It reduces performance to PIO4 levels on my system, and doesn't even work on my mdadm array anyway!

I'm all for data integrity (I use full journalling, and, IMHO, the killer feature of ext4 - Journal checksumming!) but not when it renders the filesystem unfit for purpose (Seriously... I could run stuff off a tape faster! And barriers completely subverts things like NCQ, delayed allocation, and all those other optimizing tricks to make fileystem access faster!)

mv · Advocate Joined: 20 Apr 2005 Posts: 2483

kernelOfTruth · Posted: Mon Jan 25, 2010 11:31 pm Post subject:

mv · Advocate Joined: 20 Apr 2005 Posts: 2483

mv · Advocate Joined: 20 Apr 2005 Posts: 2483

Cyker · Veteran Joined: 15 Jun 2006 Posts: 1427

Dark Foo · l33t Joined: 21 Nov 2008 Posts: 901 Location: 127.0.0.1

Shining Arcanine · Veteran Joined: 24 Sep 2009 Posts: 1110

mv · Advocate Joined: 20 Apr 2005 Posts: 2483