Re: 10K vs 15k rpm for analytics

On Mar 9, 2010, at 4:39 PM, Scott Carey wrote:

>
> On Mar 8, 2010, at 11:00 PM, Greg Smith wrote:
>
> *  At least with CentOS 5.3 and thier xfs version (non-Redhat, CentOS extras) sparse random writes could almost hang
afile system.  They were VERY slow.  I have not tested since.  
>

Just to be clear, I mean random writes to a _sparse file_.

You can cause this condition with the 'fio' tool, which will by default allocate a file for write as a sparse file,
thenwrite to it.  If the whole thing is written to first, then random writes are fine.  Postgres only writes random
whenit overwrites a page, otherwise its always an append operation AFAIK. 

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