`<html><head><meta http-equiv="Content-Type" content="text/html charset=us-ascii"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><br class=""><div><blockquote type="cite" class=""><div class="">On Mar 22, 2016, at 7:41 AM, Chris Siebenmann <<a href="mailto:cks@cs.toronto.edu" class="">cks@cs.toronto.edu</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><div class=""><blockquote type="cite" class=""><blockquote type="cite" class=""> This implicitly assumes that the only reason to set ashift=12 is<br class="">if you are currently using one or more drives that require it. I<br class="">strongly disagree with this view. Since ZFS cannot currently replace<br class="">a 512n drive with a 512e one, I feel [...]<br class=""></blockquote><br class="">*In theory* this replacement should work well if the lie works *correctly*.<br class=""> In ZoL, for the "-o ashift" is supported in "zpool replace", the<br class="">replacement should also work in mixed sector sizes.<br class=""> And in illumos the whitelist will do the same.<br class=""> What errors have you ever seen?<br class=""></blockquote><br class=""> We have seen devices that changed between (claimed) 512n and<br class="">(claimed) 512e/4k *within the same model number*; the only thing that<br class="">distinguished the two was firmware version (which is not something that<br class="">you can match in sd.conf). This came as a complete surprise to us the<br class="">first time we needed to replace an old (512n) one of these with a new<br class="">(512e) one.<br class=""><br class=""> The sd.conf whitelist also requires a reboot to activate if you need<br class="">to add a new entry, as far as I know.<br class=""><br class="">(Nor do I know what happens if you have some 512n disks and some<br class="">512e disks, both correctly recognized and in different pools, and<br class="">now you need to replace a 512n disk with a spare 512e disk so you<br class="">change sd.conf to claim that all of the 512e disks are 512n. I'd<br class="">like to think that ZFS will carry on as normal, but I'm not sure.<br class="">This makes it somewhat dangerous to change sd.conf on a live system.)<br class=""></div></div></blockquote><div><br class=""></div><div>What is missing from</div><div><a href="http://wiki.illumos.org/display/illumos/ZFS+and+Advanced+Format+disks" class="">http://wiki.illumos.org/display/illumos/ZFS+and+Advanced+Format+disks</a></div><div>is:</div><div><br class=""></div><div>1. how to change the un_phy_blocksize for any or all uns</div><div>2. how to set a default setting for all drives in sd.conf by setting attributes to</div><div> the "<vid+pid>" of "" (see sd(7d))</div><div><br class=""></div><div>I am aware of no new HDDs with 512n, so this problem will go away for HDDs.</div><div>However, there are many SSDs that work better with un_phy_blocksize = 8192</div><div>and some vendors set sd.conf or source appropriately.</div><div> -- richard</div><br class=""><blockquote type="cite" class=""><div class=""><div class=""><br class=""><blockquote type="cite" class=""><blockquote type="cite" class=""> For many usage cases, somewhat more space usage and perhaps<br class="">somewhat slower pools are vastly preferable to a loss of pool<br class="">redundancy over time. I feel that OmniOS should at least give you<br class="">the option here (in a less crude way than simply telling it that<br class="">absolutely all of your drives are 4k drives, partly because such<br class="">general lies are problematic in various situations).<br class=""></blockquote><br class="">The whitelist (sd.conf) should fit into this consideration. But not<br class="">sure how mixed sector sizes impact the performance.<br class=""></blockquote><br class=""> Oh, 512e disks in a 512n pool will probably have not great performance.<br class="">ZFS does a lot of unaligned reads and writes, unlike other filesystems;<br class="">if you say your disks are 512n, it really believes you and behaves<br class="">accordingly.<br class=""><br class=""><span class="Apple-tab-span" style="white-space:pre"> </span>- cks<br class=""></div></div></blockquote></div><br class=""></body></html>`