Disk IO issues

[Stephen John Smoogen]

On Fri, Jan 2, 2009 at 12:29 PM, Mike McGrath <mmcgrath at redhat.com> wrote:
> On Fri, 2 Jan 2009, Stephen John Smoogen wrote:
>
>> On Fri, Jan 2, 2009 at 10:57 AM, Mike McGrath <mmcgrath at redhat.com> wrote:
>> > On Fri, 2 Jan 2009, Sascha Thomas Spreitzer wrote:
>> >
>> >> Hello again,
>> >>
>> >> this line looks suspicious to me:
>> >>
>> >> # name            <active_objs> <num_objs> <objsize> <objperslab>
>> >> <pagesperslab> : tunables <limit> <batchcount> <sharedfactor> :
>> >> slabdata <active_slabs> <num_slabs> <sharedavail>
>> >> ext3_inode_cache   98472 150260    760    5    1 : tunables   54   27
>> >>   8 : slabdata  30052  30052    189
>> >>
>> >> Is it 1 big filesystem with about 1,342,177,280 inodes. Has this
>> >> amount ever be tested in the wild?
>> >
>> > Not sure if it has been tested in the wild or not but the filesystem
>> > itself contains a _TON_ of hardlinks.  Creation of hardlinks is one of the
>> > big purposes of this filesystem.
>> >
>>
>> Well then my idea of making smaller filesystems would break that
>> then... hmmm I would say that its time to escalate this to Level 2
>> support :). What do the filesystem kernel people think? I would bring
>> them in to see if there is something we are missing. Maybe something
>> in the dealing with that many inodes per file is causing a problem (or
>> maybe this is just known behaviour for large filesystems.) By the way,
>> this is a 64 bit OS correct?
>>
>
> Correct, 64 bit OS.  I'm going to get some of our FS guys on the horn as
> soon as RH is back to work.  I think most of them will return on Monday.
>

Slackers... in my day.. oh its time for my applesauce at the old
sys-admin home. Back later.

I think actually the inode/hardlink might be having an issue evne if
the files being tested aren't multiples of hardlinks. The journalling
and filesystem are going to want to optimize how they are getting
data. Hmmm if you want to completely break things... what are the
speedups/slowdowns if you mount it as ext2 instead of ext3 :).



-- 
Stephen J Smoogen. -- BSD/GNU/Linux
How far that little candle throws his beams! So shines a good deed
in a naughty world. = Shakespeare. "The Merchant of Venice"