Re: Odd blocking (or massively latent) issue - even with EXPLAIN

<p><tt><font size="2">Hi Jim,</font></tt><br /><br /><tt><font size="2">> <br />> I've already tried something
verysimilar using dd. No performance<br />> penalties during a normal running of the system - or when this
blocking<br/>> happens either actually. But I agree, it does indeed sound like some<br />> sort of I/O problem. I
justdon't know what! I do have a few more tricks<br />> up my sleeve that I'll try today. I'll post any results that
Ihave.<br /></font></tt><br /><tt><font size="2">Ok, let me know how you get on. </font></tt><br /><br /><tt><font
size="2">><br />> That latter test - won't that pretty much just read from the page cache?<br />> 'sync' may
wellhave forced dirty pages to disk but does it actually<br />> evict them to?<br /></font></tt><br /><tt><font
size="2">Basically,the cache is avoided because of the size of the file. 6000000 blocks at 8k exceeds the size of RAM
inthe machine, so it *should* miss the cache and hit the disk directly. :)</font></tt><br /><br /><tt><font
size="2">><br />> Anyway, that is off topic... perhaps ;)<br />> <br />> Thanks again,<br />> <br />>
Jim<br/>> <br /></font></tt><br /><tt><font size="2">Cheers</font></tt><br /><br /><tt><font size="2">Martin
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