Re: XFS corruption during power-blackout

[Ric Wheeler <ric@emc.com>]

Jens Axboe wrote:

>On Fri, Jul 01 2005, Bryan Henderson wrote:
>  
>
>>Wouldn't a commercial class drive that ignores explicit flushes be 
>>infamous?  I'm ready to accept that there are SCSI drives that cache 
>>writes in volatile storage by default (but frankly, I'm still skeptical), 
>>but I'm not ready to accept that there are drives out there secretly 
>>ignoring explicit commands to harden data, thus jeopardizing millions of 
>>dollars' worth of data.  I'd need more evidence.
>>    
>>
>
>I'm pretty sure I have an IBM drive that does so (its flush cache
>command is _really_ fast), as a matter of fact :-) I need to locate it
>and put it in a test box to re-ensure this.
>
>I'm not sure such drives would necessarily be infamous, hardly anyone
>would notice anything wrong in a desktop type machine. Which is what
>these drives were made for.
>  
>
One other thing to keep in mind is that drive firmware can have bugs 
just like any other bit of code, so a drive may have a bug in one 
firmware revision that gets fixed in a following one. 

I am not sure how much that other operating system uses flush cache 
commands, but until the write barrier patch,  it has been a relatively 
rarely issued command for Linux and breakage would not be noticed.