Just because a drive is writing doesn't mean a process waiting on a read
will fail.  UNIX and other multi-tasking OS's deal with situations like
this literally all the time.  There's also the same fight for every other
resource -- memory, CPU time, etc.  This is what operating systems do, and
UNIX variants do a great job of process/resource management and
scheduling.

We're talking about reads and writes taking only a fraction of a second..
not enough to cause a timeout at the application (Apache/whatever) level
or the HTTP/browser level.

To troubleshoot this problem effectively, I would set up the very same
Apache on a different port.  Use the same configuration files, but change
the port number *and* set the MaxChild to some rediculously low value (1
or 2).

Start up strace (or truss, whichever you have on your OS) and log it to a
file (note output is most likely on stderr, not stdout).  Consult
your MAN page on how to attach to an already running process. You'll want
to attach to the parent Apache process and each child.   Keep hitting the
server until it starts to flake out, then dig through the traces.  I bet
you'll find the issue there if it's not network related.

Also, try the same test on non-SSL if you're seeing it on SSL... it may
be time to look  at a later version of mod_ssl / OpenSSL if it only
happens during the SSL session.

-Steve




On Tue, 30 Apr 2002, POWERHOUSE wrote:

> Ok, I offer a different solution. Well, not a solution, but what it MAY be.
>
> First let me ask you, what type of HARD DRIVE is on this Server that this happens 
>with?
> Is it a SCSI? or a IDE? Most commonly IDE. IDE Hard Drives will have these kinds of 
>problems,
> periodically, as they can ONLY accept ONE way processes. In other words, They cannot 
>READ
> AND WRITE at the SAME TIME. So, if you have something WRITING a file, somewhere, 
>that is
> a big file, like a BIG Security Check log, it may be taking up the Drive, therefore 
>giving you this response.
> A SCSI, can both READ & WRITE. If you already on on SCSI's then this won't apply, 
>but I have
> that problem, on a LOT of websites, with EVERY browser I use(IE,Opera, and they 
>SORRY Netscape).
> I have become accustomed to when I get a page cannot be displayed, or cannot be 
>found, I try it a second
> time. However, I do get responses from people all the time, that say they had a 
>error on the page, so they
> leave, they don't try a second time. SO.... people DO lose business of this, but it 
>is NOT a OpenSRS
> problem, as I get it on websites, that have NOTHING to do with the OSRS.
>
> I suggest talking with your Technical Department, if you have a data center, if you 
>lease your servers, call
> the company that owns the servers, and tell them about it, OR if your a Reseller, 
>call the Web Hosting
> company(s) that you are resellers with, and tell them of the problem. They may say 
>it's in your head,
> but argue with them, MAKE THEM DO IT, you are the customer, or if you OWN your own 
>Data Center,
> then you are the BOSS! ;-)
>
> Anyways, Hope that offers SOME kind of light. Maybe wrong, but just what I've 
>noticed, and I too
> have been on the net for a LONG, LONG time;-).
>
> Thanks
> Richard.
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