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#1 2004-10-25 23:31:16

Paul
Member
Registered: 2004-04-12
Posts: 72

Ext2 / Ext3

Every so often, ext3 partitions are forced to be checked. This check (which analyzes the consistency of the data, rather than the consistency of the journal) takes about 30 seconds.

Since ext2 partitions are much faster than ext3 partitions, wouldn't it be best to use a non-journaled file system (given that you don't have a terabyte of storage)?

What are your thoughts?

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#2 2004-10-25 23:48:11

celeron2002
Member
From: Santiago, Chile.
Registered: 2004-02-18
Posts: 150

Re: Ext2 / Ext3

IMHO, a filesystem with journaling is 100% needed.

Try with reiserfs, is faster than ext3 and has journaling wink


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#3 2004-10-26 02:50:19

skeeterbug
Member
From: Oklahoma, USA
Registered: 2004-10-24
Posts: 92
Website

Re: Ext2 / Ext3

I also think that journaling is a very very good thing - I use ext3 but I used tune2fs to make the checks happen a little less often and I stagger the checks so that they only happen one partition at a time.

I think I used:

'tune2fs -c' to set the maximum mounts per partition to 40 or something then used 'tune2fs -C' (big C) to set /dev/hda2 to 0, /dev/hda9 to 10, /dev/hda10 to 20 and /dev/hda11 to 30.

So every ten mounts one partition gets checked, 'man tune2fs' has all the info if you're interested.  You can also use 'tune2fs -i' to set it to check on a timed basis.  Oh, you can also use tune2fs -l to see what everything is currently set to.  I assume reiser probably has the same stuff but I don't know for sure.
--
FWIW, G.S.

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#4 2004-10-26 02:52:18

Paul
Member
Registered: 2004-04-12
Posts: 72

Re: Ext2 / Ext3

Why? - if a unclean shutdown occurs, it takes 30 seconds for ext2 to recheck the data. Half a minute is not a long time. Plus, improper shutdowns do not occur very often (in my experience).

given that ext2 is quicker than journaled filesystems (since it doesn't have to write journal data):

time gained from using ext2 > time lost with fsck

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#5 2004-10-26 03:15:47

skeeterbug
Member
From: Oklahoma, USA
Registered: 2004-10-24
Posts: 92
Website

Re: Ext2 / Ext3

Well, I guess the big thing to me is the improvement in filesystem consistency or whatever - it makes me _feel_ better about it anyway.  Of course back in the day when I ran DOS I had an automatic 'scandisk' in the autoexec.bat file and it ran on every boot so maybe I'm just paranoid.

If you $searchengine for 'advantages journaling filesystems' you can find what everyone else says about it smile.

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#6 2004-10-26 03:17:51

z4ziggy
Member
From: Israel
Registered: 2004-03-29
Posts: 573
Website

Re: Ext2 / Ext3

thats a very good point, considering not many ppl actually USE  the journaling capabilities...

coming from the iSeries (as/400) world i know that journaling is not something u would normally want for heavy duty system, unless it is highly sensitive data, and even then, u will customize it specifically for the target file. with that said - i have no idea how to use journaling on linux, and i doubt i ever will on my pc... (on servers, oh well...thats a different story wink )

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#7 2004-10-26 03:38:56

paranoos
Member
From: thornhill.on.ca
Registered: 2004-07-22
Posts: 442

Re: Ext2 / Ext3

all the benchmarks i've seen say reiser, xfs, and jfs are faster than ext2. ext3 is much slower.

also, reiser doesn't check the filesystem on bad shutdown.

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#8 2004-10-26 04:37:47

cactus
Taco Eater
From: t͈̫̹ͨa͖͕͎̱͈ͨ͆ć̥̖̝o̫̫̼s͈̭̱̞͍̃!̰
Registered: 2004-05-25
Posts: 4,615
Website

Re: Ext2 / Ext3

journaling filesystems create a journal log of what is being done in the filesystem (ie what is being written to disk and what is not). This way, the writes are nearly atomic--insofar as there is a journal covering what was done and what was left to be done.

In the event of a crash during mid write, with a journaling system that data can be recoved, using the information in the journal--much shorted fsck time. With a non-journaling system (ext2), an fsck fo the entire volume must be performed to return the disk to consistency. This can take a LONG time on today's large volumes.

Just because you don't fsck when you need to doesn't mean you don't need to.
I like knowing that I have a robust filesystem underneath (journaling). I use reiserfs, becuase the fsck action is really quite quick, and I am not so impatient as to care about the 20 seconds spend every odd number of reboots, compared to a disk with gobs of crap data (and lost data) on it from one crash.
But, to each their own. I guess it is like wearing a life jacket while rafting down a river. Sure, you might not need it...but if you do end up needing it and don't have it on...you die.

This is a simplistic view of what is happening. For more info check here.
http://bulma.net/body.phtml?nIdNoticia=1154
http://www.linuxgazette.com/issue55/florido.html
http://oregonstate.edu/~kveton/fs/
http://www.stanchina.net/~flavio/linux/ … g-FAQ.html
http://freshmeat.net/articles/view/212/
http://olstrans.sourceforge.net/release … -ext3.html

probably more than you ever wanted to know about journaling.  :twisted:


"Be conservative in what you send; be liberal in what you accept." -- Postel's Law
"tacos" -- Cactus' Law
"t̥͍͎̪̪͗a̴̻̩͈͚ͨc̠o̩̙͈ͫͅs͙͎̙͊ ͔͇̫̜t͎̳̀a̜̞̗ͩc̗͍͚o̲̯̿s̖̣̤̙͌ ̖̜̈ț̰̫͓ạ̪͖̳c̲͎͕̰̯̃̈o͉ͅs̪ͪ ̜̻̖̜͕" -- -̖͚̫̙̓-̺̠͇ͤ̃ ̜̪̜ͯZ͔̗̭̞ͪA̝͈̙͖̩L͉̠̺͓G̙̞̦͖O̳̗͍

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#9 2004-10-26 15:27:20

Paul
Member
Registered: 2004-04-12
Posts: 72

Re: Ext2 / Ext3

cactus wrote:

I use reiserfs, becuase the fsck action is really quite quick, and I am not so impatient as to care about the 20 seconds spend every odd number of reboots, compared to a disk with gobs of crap data (and lost data) on it from one crash.

But, to each their own. I guess it is like wearing a life jacket while rafting down a river. Sure, you might not need it...but if you do end up needing it and don't have it on...you die.

To say that a non journaled filesystem leaves "gobs of crap data (and lost data) on it from one crash, and imply that a journaled filesystem doesn't is wrong. They both will have the same inconsistencies, but one will be quicker to repair the problem.

The reason why I started this topic was because I noticed the fsck for an ext2 partition was quite quick. Given that unclean shutdowns don't occur often (which they don't for me), one would think that using ext2 would be preferable to ext3.

Thank-you for your replies.

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#10 2004-10-26 15:43:32

dadexter
Member
From: Dorval, QC, Canada
Registered: 2004-09-07
Posts: 274
Website

Re: Ext2 / Ext3

From what I have read, ext3 is an horrible idea... an ext2 filesystem with a journal on top... so it will not be much faster than ext2... and has the same limitations (no files bigger than 2GB or something)...


Now on the other hand reiserfs is alot faster than ext2/3

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#11 2004-10-30 05:34:11

Xentac
Forum Fellow
From: Victoria, BC
Registered: 2003-01-17
Posts: 1,797
Website

Re: Ext2 / Ext3

I have an 80 gig hard drive with /home on it.  I haven't yet tweaked it for no fsck after a certain number of mounts.  It takes more than just 30 seconds to scan (I have anywhere from 15-1 gig free on it at any given time).  In the case of a crash, a journaled filesystem will come back much faster than something without a journal.


I have discovered that all of mans unhappiness derives from only one source, not being able to sit quietly in a room
- Blaise Pascal

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