ecryptfs team mailing list archive

["Volodymyr M. Lisivka" <vlisivka@xxxxxxxxx>]

> Hopefully neither is true, but in that case, the chances of a file
getting replaced by a zero-length file are very small indeed.

I expect that Ext4 is much better in performance than Ext3 and will save
me about 1 minute per day in average, (6 hours per year - about 1
additional working day), which is very good.

On other hand, I can lose few hours per data corruption, which is
comparable. My notebook has some problems with restoring from Hiberante
(no proprietary code at my notebook at all), so unexpected hangups in
few minutes after restore are common to me (2-3 per month), thus I can
loss few days per year with Ext4 - about a working week.

Formula to calculate actual benefit: benefit_value*benefit_probability -
loss_value*loss_probability [ - loss_value*loss_probability ]..., where
is benefit_probability

For Ext3: benefit_value is zero comparing to Ext4 (Ext3 is slower than
Ext4), but loss_value is small too - about 1 minute per failure.

Ext3_benefit = 0*(1-k) - 1m*k; where k is probability of failure per working day;
Ext4_benefit = 1m*(1-k) - 2h*k;

If you see failures less than twice a year, then Ext4 is better for you.
If you see failures more than twice a year, then Ext3 is better.

> And again, I will note that XFS has been doing this all along, and
other newer file systems will also be doing delayed allocation, and will
be subject to the same pitfalls. Maybe they will also encode the same
hacks to work around broken expectations, and people with crappy
proprietary binary drivers. But folks really shouldn't be counting on
this....

I, personally, have very bad experience with XFS. We used it on
linux.org.ua site and I spent few days of my short life to fix corrupted
files manually after few power failures in data centre (all files are
created or modified recently, so backup is not helpful in this case). I
recommend to stay away from XFS or similar filesystems in favour of
Ext3, which has optimal balance between speed and robustness.

I used crash test in 2003 to check maturity of Ext3 filesystem. I set up
computer to soft reset itself every 5 minutes, while executing
filesystem intensive operations, and then left it for few days
(Thursday-Monday). Ext3 is passed that test just fine.

Can we create few test cases with common filesystem usage patterns and
run them continuously in Qemu on raw device and then use "pkill -9 qemu;
qemu &" to simulate crash and restart? Such crash test can help much
better than talks about this problem. Run it for few days to gather
statistic about number of data corruption problems per failure.

-- 
Ext4 data loss
https://bugs.launchpad.net/bugs/317781
You received this bug notification because you are a member of eCryptfs,
which is subscribed to ecryptfs-utils in ubuntu.

Status in “ecryptfs-utils” source package in Ubuntu: Invalid
Status in “linux” source package in Ubuntu: Confirmed
Status in ecryptfs-utils in Ubuntu Jaunty: Invalid
Status in linux in Ubuntu Jaunty: Confirmed

Bug description:
I recently installed Kubuntu Jaunty on a new drive, using Ext4 for all my data.

The first time i had this problem was a few days ago when after a power loss ktimetracker's config file was replaced by a 0 byte version . No idea if anything else was affected.. I just noticed ktimetracker right away.

Today, I was experimenting with some BIOS settings that made the system crash right after loading the desktop. After a clean reboot pretty much any file written to by any application (during the previous boot) was 0 bytes.
For example Plasma and some of the KDE core config files were reset. Also some of my MySQL databases were killed...

My EXT4 partitions all use the default settings with no performance tweaks. Barriers on, extents on, ordered data mode..

I used Ext3 for 2 years and I never had any problems after power losses or system crashes.

Jaunty has all the recent updates except for the kernel that i don't upgrade because of bug #315006

ProblemType: Bug
Architecture: amd64
DistroRelease: Ubuntu 9.04
NonfreeKernelModules: nvidia
Package: linux-image-2.6.28-4-generic 2.6.28-4.6
ProcCmdLine: root=UUID=81942248-db70-46ef-97df-836006aad399 ro rootfstype=ext4 vga=791 all_generic_ide elevator=anticipatory
ProcEnviron:
 LANGUAGE=
 LANG=en_US.UTF-8
 SHELL=/bin/bash
ProcVersionSignature: Ubuntu 2.6.28-4.6-generic
SourcePackage: linux