<font face="arial">Hi Antonio,<br><br>I think this problem can also happen for non-OS disks. Considering that we access a non-OS disk , we can have pages in memory that belong to this disk. In that case, the system may ask to flush these "dirty" pages to the non-OS disk. And here we are: potential deadlock as I explain in my first post.<br>I hope this clarify the problem.<br><br>Correct me if I have made wrong assumptions, I just want to have the conviction that this cannot happen in production.<br><br>Ivan<br><br><br>At Tuesday, 01/02/2011 on 17:44 Antonio Anselmi wrote:<br><blockquote style="border:0;border-left: 2px solid #22437f; padding:0px; margin:0px; padding-left:5px; margin-left: 5px; ">OS disk is usually a local device and not managed by drbd, i.e. is not<br>
a backing device.<br>
Unless I'm missing something about your question.<br>
<br>
Antonio<br>
<br>
<br>
--<br>
Lo scopo del lavoro รจ quello di guadagnarsi il tempo libero (Aristotele)<br>
The purpose of the job is to gain leisure (Aristotele)<br>
<br>
<br>
<br>
<br>
2011/2/1 Ivan Frain <ivan.frain@euranova.eu>:<br>
> Hi all,<br>
><br>
> I am currently evaluating DRBD as a storage candidate for highly available<br>
> storage in a virtualized environment.<br>
> It seems like a very good alternative to expensive SAN/NAS.<br>
> I was wondering how DRBD deals with the network block device deadlock<br>
> problem.<br>
> This problem (described here: <a href="http://lwn.net/Articles/195416" target="_blank" class="normal-link">http://lwn.net/Articles/195416</a>/) can be<br>
> summarized as follows: if the system runs short in memory, it will try to<br>
> write dirty page to disk in order to free memory space. if the disk is a<br>
> network block device, the dirty page write may need to allocate some other<br>
> memory pages which is not possible since the solution to have more memory<br>
> available was to write the dirty page to disk.<br>
><br>
> If someone has some information about that problem I'am eager to read it.<br>
><br>
> Thank you in advance.<br>
><br>
> BR,<br>
> Ivan<br>
><br>
><br>
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