Re: XFS filesystem corruption

Julien FERRERO
2013-03-08T10:16:32Z

>
> Yes they were. XFS had barrier support added in 2.6.15.
>

The XFS was running over a software RAID0 or software RAID5 depending
on the product. In both case, my understanding is that either software
RAID0 or software RAID5 did not support barrier in 2.6.18.

> Yes, that would have been me that said that. I started seeing lots
> of boy-racer "tweak your filesystem to go faster" blogs recommending
> that unwritten extents should be turned off high up in google
> results, with numbers to prove that it improved performance.
>
> There were two common things wrong with these blogs:
>
> 1. None of them mentioned that turning off unwritten extents
> exposes stale data to users. i.e. a whopping great big
> security hole.
>
> 2. they reported significant performance improvements for
> workloads that *didn't use unwritten extents* when they set
> this flag. i.e. they mistook run-to-run variablity of the
> benchmark for a performance improvement. i.e. Benchmarking
> 101 Fail.
>
> When you get people who do not understand what they are doing and
> giving bad advice as the first 10 hits for a google search about
> optimising/tuning XFS filesystems, it's a major concern, and so I
> took steps to ensure you can't turn off unwritten extents with
> mkfs...

Thanks for the explanation.