[Ocfs2-devel] 40TB RAID and OCFS2 woes (inode64, JDB2, huge partition support, Volume might try to write to blocks beyond what jbd can address in 32 bits)

[Robert Smith]

I can delete the file, but it takes hours to recreate, so I figured that I'd run any tests you guys want to see first.

-Robert

On Jan 3, 2010, at 5:19 AM, Joel Becker wrote:

> On Sat, Jan 02, 2010 at 04:47:58AM +0900, Robert Smith wrote:
>> Just thought I would let you guys know that creating a 20TB file was successful. I even appended data to the end of it. Any operations on the file are completely useless because they take way to long. A appended "hello" to the end of the file no problem, but tail -n 1 {filename} yielded nothing except a lot of disk read after 159minutes of waiting.
> 
> 	Wow, that's a lot of waiting.  I suspect it's the fault of
> tail(1).  You asked for the last line of the file (tail -1).  I bet
> tail(1) is reading the entire file line-by-line in order to calculate
> the last line.  This has to be much slower than reading it at optimal
> hunks (with your 500MB/s disks).  Conversely, appending is easy because
> the kernel just starts at the end of the file.  No need to read the
> existing 20TB.
> 	What other operations are 'completely useless'?  The expectation
> would be that random I/O is as fast as ever.  How long does deleting
> take?
> 
> Joel
> 
> -- 
> 
> "The trouble with being punctual is that nobody's there to
> appreciate it."
> 	- Franklin P. Jones
> 
> Joel Becker
> Principal Software Developer
> Oracle
> E-mail: joel.becker at oracle.com
> Phone: (650) 506-8127