ext4 and data loss [LWN.net]

ext4 and data loss

Posted Mar 13, 2009 5:19 UTC (Fri) by qg6te2 (guest, #52587)
In reply to: ext4 and data loss by SLi
Parent article: ext4 and data loss

While it's in a sense unfortunate that in ext4 this happening is more likely than in ext3 (and it's exactly that, it's still very possible in ext3), applications relying in that not happening are broken even in ext3-land

An appeal can be made to have better written applications, or more practically, an acceptance can be made that in the real world apps are never perfect. A file system needs to deal with that (no matter what is guaranteed by POSIX) and provide a reasonable trade-off between speed and safety.

In the case of ext3, whether by side effect or design, this trade-off is at a good point. Mounting with the "sync" option sacrifices too much speed, while in the current version of ext4 the trade-off is too aggressively in the direction of speed. Not everybody can afford a UPS, nor should a UPS be required to have a disk with sane contents after a crash.

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ext4 and data loss

Posted Mar 13, 2009 13:17 UTC (Fri) by jwarnica (subscriber, #27492) [Link]

Not everyone can afford a computer, either. List price for the smallest APC UPS that includes software is $59.99. Which is pretty cheep. Given the other benefits of UPSs, providing some surge and brownout protection, not having one is just stupid.

General purpose distros assume that you have what, a gig or two of memory. Not everyone can afford memory, either. And there are special case systems which would never have that kind of memory. So if you have a shitty computer, you run either older versions, or specially targeted distros. And if you are building an embedded system, you make choices appropriately.

In 2009, if you choose to have a crippled system that doesn't have a UPS, then choose your filesystem carefully.

ext4 and data loss

Posted Mar 13, 2009 16:43 UTC (Fri) by SLi (subscriber, #53131) [Link]

I think ext4's tradeoff is a very sane one. I don't expect my machine to
crash all the time (in fact I can't remember when it last did, must have
been in something like 2005). If it gives a speedup measured in tens of
percents, it's the only sane thing to do.

And for the case when it's not sane, there's f(data)sync().