<br><font size=2 face="sans-serif">We are doing SEEK_SET</font>
<br>
<br><font size=2 face="sans-serif">fseek(fp,offset[i],SEEK_SET</font>
<br>
<br><font size=2 face="sans-serif">We were running into this same issue
on our san file system until we set the dma_cache_read_ahead to match our
buffer size of 256k. Just wondering if there is away to set that
within lustre. We are running 1.8 on the MDS and OSS and the clients
running the fseek are are running 1.6</font>
<br>
<br><font size=2 face="sans-serif">Thanks again.</font>
<br>
<br>
<br><font size=2 face="sans-serif"><br>
Rocky</font>
<br>
<br>
<br>
<table width=100%>
<tr valign=top>
<td><font size=1 color=#5f5f5f face="sans-serif">From:</font>
<td><font size=1 face="sans-serif">Andreas Dilger <andreas.dilger@oracle.com></font>
<tr valign=top>
<td><font size=1 color=#5f5f5f face="sans-serif">To:</font>
<td><font size=1 face="sans-serif">Ronald K Long <rklong@usgs.gov></font>
<tr>
<td valign=top><font size=1 color=#5f5f5f face="sans-serif">Cc:</font>
<td><font size=1 face="sans-serif">lustre-discuss@lists.lustre.org</font>
<tr valign=top>
<td><font size=1 color=#5f5f5f face="sans-serif">Date:</font>
<td><font size=1 face="sans-serif">04/09/2010 10:52 AM</font>
<tr valign=top>
<td><font size=1 color=#5f5f5f face="sans-serif">Subject:</font>
<td><font size=1 face="sans-serif">Re: [Lustre-discuss] fseeks on lustre</font></table>
<br>
<hr noshade>
<br>
<br>
<br><tt><font size=2>On 2010-04-07, at 14:09, Ronald K Long wrote:<br>
> I am having an issue with our lustre file system. In our current
<br>
> environment on a san file system opening a large file and doing <br>
> fseeks completes in under 2 seconds. Running that same routine
on <br>
> our lustre file system the routine actually never finishes.<br>
<br>
Doing fseek() itself is only a client-side operation, so it should <br>
have no performance impact, UNLESS you are doing SEEK_END, which <br>
requires that the actual file size be computed on the client. That
<br>
causes lock revocation from all of the clients and is an expensive <br>
operation. Using SEEK_CUR or SEEK_SET has no cost at all.<br>
<br>
> Are there any tunable parameter in lustre that can alleviate this
<br>
> problem?<br>
<br>
It depends on what the problem really is.<br>
<br>
Cheers, Andreas<br>
--<br>
Andreas Dilger<br>
Principal Engineer, Lustre Group<br>
Oracle Corporation Canada Inc.<br>
<br>
</font></tt>
<br>
<br>