On 10/26/2014 09:26 AM, Brian Foster wrote:
> On Sat, Oct 25, 2014 at 04:26:54PM -0500, Stan Hoeppner wrote:
>> On 10/25/2014 01:56 PM, Richard Scobie wrote:
>>> Stan Hoeppner said:
>>>> How can I disable or change the filestreams behavior so all files go
>>>> into the one AG for the single directory test?
>>> Hi Stan,
>>> Instead of mounting with -o filestreams, would using the chattr flag
>>> instead help?
>> That won't help. That turns it on (if it's not enabled by default these
>> days). I need to turn off the behavior I'm seeing, whether it's due to
>> the filestreams allocator or default inode64. Then again it may not be
>> possible to turn it off...
>> Anyone have other ideas on how to accomplish my goal? Parallel writes
>> to a single AG on the outer platter edge vs the same to all AGs across
>> the entire platter? I'm simply trying to demonstrate the differences in
>> aggregate bandwidth due to the extra seek latency of all AGs case.
> What about just preallocating the files? Obviously this removes block
> allocation contention from your experiment, but it's not clear if that's
> relevant to your test. If I create a smaller, but analogous fs to yours,
> I seem to get this behavior from just doing an fallocate of each file in
> E.g., Create directory 0, fallocate 44 files all of which end up in AG
> 0. Create directory 1, fallocate 44 files which end up in AG 1, etc.
> From there you can do direct I/O overwrites to 44 files across each AG
> or 44 files in any single AG.
I figured preallocating would get me what I want but I've never used
fallocate, nor dd into fallocated files. Is there anything special
required here with dd, or can I simply specify the filename to dd, and
make sure bs + count doesn't go beyond EOF?