<div dir="ltr"><br><div class="gmail_extra"><br><div class="gmail_quote">On Wed, Jul 6, 2016 at 2:27 PM, Nir Soffer <span dir="ltr"><<a href="mailto:nsoffer@redhat.com" target="_blank">nsoffer@redhat.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><span class="">On Wed, Jul 6, 2016 at 12:18 AM, David Twersky <<a href="mailto:dmtwersky@gmail.com">dmtwersky@gmail.com</a>> wrote:<br>
> We use a lot of flash arrays, and some of them require that devices be 4k<br>
> aligned, is it possible to create a Fibre Channel Storage Domain and have it<br>
> 4k aligned?<br></span></blockquote><div><br></div><div>Is it required or preferred? Because while most of our data is 4K aligned, some writes aren't - mainly metadata of the storage domain.</div><div>So you won't be usually suffering from mis-aligned writes (or reads) which are costly, but we must be able to perform atomic 512b writes (which may translate to a read-modify-write of course in the flash).</div><div><div>I'm not sure what we expose to VMs, btw - if we can expose to them 4K drive...?</div></div><div><br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><span class="">
<br>
</span>I don't think we support this.<br></blockquote><div><br></div><div>Indeed - we assume sector size to be 512b in the code:</div><div>lib/vdsm/storage/constants.py:SECTOR_SIZE = 512</div><div><br></div><div>Can you use a direct LUN, though?</div><div>Y.<br></div><div> </div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
<br>
For example, we assume that writing 512 bytes blocks is atomic, if these<br>
writes will fail because the minimal block is 4k, block storage metadata<br>
operations will fail.<br>
<br>
Anyway, why not try to add such lun and create a storage domain for testing?<br>
<br>
Nir<br>
_______________________________________________<br>
Users mailing list<br>
<a href="mailto:Users@ovirt.org">Users@ovirt.org</a><br>
<a href="http://lists.ovirt.org/mailman/listinfo/users" rel="noreferrer" target="_blank">http://lists.ovirt.org/mailman/listinfo/users</a><br>
</blockquote></div><br></div></div>