<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; "><div><div>On Feb 17, 2014, at 2:48 PM, Derek Yarnell <<a href="mailto:derek@umiacs.umd.edu">derek@umiacs.umd.edu</a>> wrote:</div><br class="Apple-interchange-newline"><blockquote type="cite">Hi,<br><br>So we bought a new Dell R720xd with 2 Dell SLC SSDs which were shipped<br>as a Pliant-LB206S-D323-186.31GB via format. </blockquote><div><br></div><div>Pliant SSDs (note: Pliant was purchased by Sandisk in 2011) are optimized for</div><div>lots of concurrent I/O operations. This is not the kind of workload generated by</div><div>the ZIL, which is more contiguous, single thread-like.</div><br><blockquote type="cite"> The bulk of the storage is<br>just a 6+2 RaidZ2 with 3TB disks. When doing a simple untar (40MB/2000<br>files) over NFS (synchronous IO) having the mirrored slog of Pliant SSDs<br>seems to offer horrendous performance. On the order of 18-20 OPs per<br>second (via zpool iostat -v 1). </blockquote><div><br></div><div>Never ever use zpool iostat to measure application performance. zpool iostat</div><div>measures workload to the vdevs, showing back-end operations to disk. As such</div><div>there is no correlation to client-side operations of any sort, especially writes and</div><div>metadata updates. You'll need to go up the stack and see what it is doing. For NFS</div><div>I highly recommend nfssvrtop. To see the response time of the Pliant, use "iostat -x"</div><div>or, as I prefer, "iostat -zxCn"</div><div><br></div><div>Note: response time (measured by iostat -x as a variant of "svc_t") is the critical </div><div>measurement for NFS workloads. Bandwidth is almost meaningless in analyzing</div><div>NFS.</div><br><blockquote type="cite"> We have a number of other ZFS builds<br>with ZeusRAM slogs and they work very well and while the Pliant may not<br>be as good a choice it shouldn't be as bad as this.<br></blockquote><div><br></div><div>It can be as bad as that.</div><br><blockquote type="cite"># zfs get sync,dedup,logbias,compression,checksum zpool0<br>NAME PROPERTY VALUE SOURCE<br>zpool0 sync standard default<br>zpool0 dedup off default<br>zpool0 logbias latency default<br>zpool0 compression off default<br>zpool0 checksum on default<br><br>Adding a ramdisk slog device makes everything perform as expected.<br></blockquote><div><br></div><div>yep. A ZeusRAM will also help.</div><div> -- richard</div><br><blockquote type="cite">Setting sync=disabled of course makes things all better.<br><br># zpool status zpool0<br> pool: zpool0<br> state: ONLINE<br> scan: none requested<br>config:<br><br> NAME STATE READ WRITE CKSUM<br> zpool0 ONLINE 0 0 0<br> raidz2-0 ONLINE 0 0 0<br> c1t5000C50057EC4B73d0 ONLINE 0 0 0<br> c1t5000C50057EC6EABd0 ONLINE 0 0 0<br> c1t5000C50057EC7CB7d0 ONLINE 0 0 0<br> c1t5000C50057EC8F23d0 ONLINE 0 0 0<br> c1t5000C50057EC998Bd0 ONLINE 0 0 0<br> c1t5000C50057ECB1BBd0 ONLINE 0 0 0<br> c1t5000C50057ECFEE7d0 ONLINE 0 0 0<br> c1t5000C50057ED03F7d0 ONLINE 0 0 0<br> logs<br> mirror-1 ONLINE 0 0 0<br> c3t5001E820026DA2CAd0 ONLINE 0 0 0<br> c3t5001E820026DA45Ad0 ONLINE 0 0 0<br><br>errors: No known data errors<br><br><br>-- <br>Derek T. Yarnell<br>University of Maryland<br>Institute for Advanced Computer Studies<br>_______________________________________________<br>OmniOS-discuss mailing list<br><a href="mailto:OmniOS-discuss@lists.omniti.com">OmniOS-discuss@lists.omniti.com</a><br>http://lists.omniti.com/mailman/listinfo/omnios-discuss<br></blockquote></div><br><div apple-content-edited="true"> <div style="color: rgb(0, 0, 0); font-family: Helvetica; font-size: medium; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-align: -webkit-auto; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><span class="Apple-style-span" style="border-collapse: separate; color: rgb(0, 0, 0); font-family: Helvetica; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-align: -webkit-auto; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; border-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; font-size: medium; "><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><span class="Apple-style-span" style="border-collapse: separate; color: rgb(0, 0, 0); font-family: Helvetica; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-align: -webkit-auto; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; border-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; font-size: medium; "><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><span class="Apple-style-span" style="border-collapse: separate; color: rgb(0, 0, 0); font-family: Helvetica; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-align: -webkit-auto; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; border-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; font-size: medium; "><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><span class="Apple-style-span" style="border-collapse: separate; color: rgb(0, 0, 0); font-family: Helvetica; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-align: -webkit-auto; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; border-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; font-size: medium; "><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; ">--</div><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><br></div><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><a href="mailto:Richard.Elling@RichardElling.com">Richard.Elling@RichardElling.com</a><br>+1-760-896-4422<br><br><br></div></span></div></span></div></span></div></span></div> </div> <br></body></html>