Re: Converting system to raid

[jim owens <jowens@hp.com>]

To continue the pointless (but maybe entertaining) argument :)

Jeff Garzik wrote:
> jim owens wrote:
>> The filesystem mod-time might have nanoseconds in it, but
>> that does not mean 2 writes 100 nanoseconds apart will have
>> different mod-times.
> 
> Modern Linux filesystems absolutely do do metadata updates at that level 
> of granularity.

In filesystems it only counts if it makes it to disk.

10,000,000 write-to-disk metadata updates per second?  I think not.

Even the top-of-the-line intel ssd can only do 3,300 writes per second.

> Are you guaranteed district timestamps between writes?  No, but then 
> again, metadata updates were never guaranteed between two writes either. 
>  You might just be dirtying a mmap'd page, for example.

So this sounds like you at least agree with my original statement
that mod-time is not a 100% guarantee that no write occurred after
you read a particular block of a file.  Regardless of the fact we
disagree about how accurate filesystems record times.

jim