<div dir="ltr"><div class="gmail_extra"><br><div class="gmail_quote">On Mon, Sep 29, 2014 at 6:14 PM, Andrew M. Hettinger <span dir="ltr"><<a href="mailto:AHettinger@prominic.net" target="_blank">AHettinger@prominic.net</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"><div>
<p><tt><font>Bob Friesenhahn <<a href="mailto:bfriesen@simple.dallas.tx.us" target="_blank">bfriesen@simple.dallas.tx.us</a>> wrote on 09/29/2014 05:57:26 PM:<span class=""><br>
<br>
> How would ZFS know if the data stored is "incorrect" from the user's <br>
> perspective?<br>
> <br>
</span></font></tt><br>
<tt><font>Presumably because the checksum is wrong. </font></tt></p></div></blockquote><br></div>Exactly, if the data is returned incorrect from the SSD ZFS will detect it via checksum. It will then rebuild from the raidz1 parity, if that fails it will return a data read error.<br></div><div class="gmail_extra"><br></div><div class="gmail_extra">In relation to the original topic, with 163 days uptime, the scratch pool has had zero checksum errors. It gets completely rewritten about twice a week on average. At its peak usage it was rewritten daily for about 45 days.<br><br><span style="font-family:courier new,monospace">root@hcp-iops1:~# uptime<br> 07:44am up 163 days 20:57, 1 user, load average: 0.13, 0.15, 0.16<br>root@hcp-iops1:~# zpool status scratch<br> pool: scratch<br> state: ONLINE<br> scan: scrub repaired 0 in 7h59m with 0 errors on Sat Sep 6 00:59:21 2014<br>config:<br><br> NAME STATE READ WRITE CKSUM<br> scratch ONLINE 0 0 0<br> raidz1-0 ONLINE 0 0 0<br> c1t500253855035D1B1d0s0 ONLINE 0 0 0<br> c1t500253855035D12Fd0s0 ONLINE 0 0 0<br> c1t500253855035D114d0s0 ONLINE 0 0 0<br> c1t500253855035D10Ed0s0 ONLINE 0 0 0<br> c1t500253855035D109d0s0 ONLINE 0 0 0<br> raidz1-1 ONLINE 0 0 0<br> c1t500253855035D1C1d0s0 ONLINE 0 0 0<br> c1t500253855035D1C0d0s0 ONLINE 0 0 0<br> c1t500253855035D1BFd0s0 ONLINE 0 0 0<br> c1t500253855035D1BEd0s0 ONLINE 0 0 0<br> c1t500253855035D1B5d0s0 ONLINE 0 0 0<br> raidz1-2 ONLINE 0 0 0<br> c1t500253855035D1E3d0s0 ONLINE 0 0 0<br> c1t500253855035D1E1d0s0 ONLINE 0 0 0<br> c1t500253855035D1C8d0s0 ONLINE 0 0 0<br> c1t500253855035D1C6d0s0 ONLINE 0 0 0<br> c1t500253855035D1C3d0s0 ONLINE 0 0 0<br> raidz1-3 ONLINE 0 0 0<br> c1t500253855035D8C0d0s0 ONLINE 0 0 0<br> c1t500253855035D8BDd0s0 ONLINE 0 0 0<br> c1t500253855035D1F6d0s0 ONLINE 0 0 0<br> c1t500253855035D1E6d0s0 ONLINE 0 0 0<br> c1t500253855035D1E5d0s0 ONLINE 0 0 0<br> raidz1-4 ONLINE 0 0 0<br> c1t500253855035D8C7d0s0 ONLINE 0 0 0<br> c1t500253855035D8C6d0s0 ONLINE 0 0 0<br> c1t500253855035D8C3d0s0 ONLINE 0 0 0<br> c1t500253855035D8C2d0s0 ONLINE 0 0 0<br> c1t500253855035D8C1d0s0 ONLINE 0 0 0<br> raidz1-5 ONLINE 0 0 0<br> c1t500253855035E2F6d0s0 ONLINE 0 0 0<br> c1t500253855035E2F5d0s0 ONLINE 0 0 0<br> c1t500253855035E2ECd0s0 ONLINE 0 0 0<br> c1t500253855035E2EBd0s0 ONLINE 0 0 0<br> c1t500253855035E2D7d0s0 ONLINE 0 0 0<br> raidz1-6 ONLINE 0 0 0<br> c1t500253855035F484d0s0 ONLINE 0 0 0<br> c1t500253855035F483d0s0 ONLINE 0 0 0<br> c1t500253855035F480d0s0 ONLINE 0 0 0<br> c1t500253855035F472d0s0 ONLINE 0 0 0<br> c1t500253855035F46Fd0s0 ONLINE 0 0 0<br> raidz1-7 ONLINE 0 0 0<br> c1t5002538550363742d0s0 ONLINE 0 0 0<br> c1t500253855036373Ed0s0 ONLINE 0 0 0<br> c1t50025385503633BDd0s0 ONLINE 0 0 0<br> c1t5002538550363164d0s0 ONLINE 0 0 0<br> c1t500253855035F489d0s0 ONLINE 0 0 0<br> raidz1-8 ONLINE 0 0 0<br> c1t500253855036378Ad0s0 ONLINE 0 0 0<br> c1t5002538550363789d0s0 ONLINE 0 0 0<br> c1t5002538550363786d0s0 ONLINE 0 0 0<br> c1t500253855036374Cd0s0 ONLINE 0 0 0<br> c1t500253855036374Bd0s0 ONLINE 0 0 0<br> raidz1-9 ONLINE 0 0 0<br> c1t500253855035D1F4d0s0 ONLINE 0 0 0<br> c1t500253855035D1ECd0s0 ONLINE 0 0 0<br> c1t500253855035D1E2d0s0 ONLINE 0 0 0<br> c1t500253855035D1DAd0s0 ONLINE 0 0 0<br> c1t500253855035D1B2d0s0 ONLINE 0 0 0<br> raidz1-10 ONLINE 0 0 0<br> c1t500253855035D12Dd0s0 ONLINE 0 0 0<br> c1t500253855035D8C8d0s0 ONLINE 0 0 0<br> c1t500253855035D8C5d0s0 ONLINE 0 0 0<br> c1t500253855035D8C4d0s0 ONLINE 0 0 0<br> c1t500253855035D1F8d0s0 ONLINE 0 0 0<br> raidz1-11 ONLINE 0 0 0<br> c1t5002538550363793d0s0 ONLINE 0 0 0<br> c1t500253855035E2DBd0s0 ONLINE 0 0 0<br> c1t500253855035E2DAd0s0 ONLINE 0 0 0<br> c1t500253855035E2D9d0s0 ONLINE 0 0 0<br> c1t500253855035D12Ed0s0 ONLINE 0 0 0<br> spares<br> c1t5002538550363794d0s0 AVAIL<br> c1t5002538550363797d0s0 AVAIL<br> c1t500253855035E2D8d0s0 AVAIL<br><br>errors: No known data errors</span><br></div></div>