<html><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><br><div><div>On 14/05/2009, at 8:26 PM, Sam Hadley-Jones wrote:</div><br class="Apple-interchange-newline"><blockquote type="cite"><div><blockquote type="cite"><br></blockquote><blockquote type="cite">I'm really surprised at your freeze up issues. I'm using ext3 and slow<br></blockquote><blockquote type="cite">deletes and no longer have any playback issues.<br></blockquote><blockquote type="cite"><br></blockquote><blockquote type="cite">Did you have a chance to run some performance tests on the raid5 array<br></blockquote><blockquote type="cite">like I suggested as i'm wondering if you have other issues.<br></blockquote><blockquote type="cite"><br></blockquote><blockquote type="cite">--------------------------------------------<br></blockquote><blockquote type="cite">Steven Ellis - Technical Director<br></blockquote><blockquote type="cite">OpenMedia Limited - The Home of myPVR<br></blockquote><blockquote type="cite">email - <a href="mailto:steven@openmedia.co.nz">steven@openmedia.co.nz</a><br></blockquote><blockquote type="cite">website - <a href="http://www.openmedia.co.nz">http://www.openmedia.co.nz</a><br></blockquote><blockquote type="cite"><br></blockquote><br>Here's some test results. A word of warning to any newbies here that would<br>like to do similar benchmarking; dd is a very powerful command and can kill<br>data indiscriminately with the most minor typo with no<br>confirmation/warning. <br><br>Just a recap, this is 5x 500GB Western Digital Green Power SATA drives in<br>RAID 5 as /dev/md0. Three are connected to the motherboard SATA connectors<br>and the remaining two to a PCIe SATA card. LVM storage group on top with a<br>single PV. <br><br>mounted:<br>/dev/mapper/storage-main on /storage type reiserfs (rw)<br>/dev/mapper/storage-tv on /tv type xfs (rw,allocsize=512m)<br><br>Raw drive member of array:<br><br>sam@mediabox:~$ sudo dd if=/dev/sda of=/dev/null bs=1048576 count=1024<br>1024+0 records in<br>1024+0 records out<br>1073741824 bytes (1.1 GB) copied, 16.8546 s, 63.7 MB/s<br><br>Raw RAID5 array:<br><br>sam@mediabox:~$ sudo dd if=/dev/md0 of=/dev/null bs=1048576 count=1024<br>1024+0 records in<br>1024+0 records out<br>1073741824 bytes (1.1 GB) copied, 13.9099 s, 77.2 MB/s<br><br>LVM LV:<br><br>sam@mediabox:~$ sudo dd if=/dev/storage/main of=/dev/null bs=1048576<br>count=1024<br>1024+0 records in<br>1024+0 records out<br>1073741824 bytes (1.1 GB) copied, 21.7457 s, 49.4 MB/s<br><br>Filesystem on LV 'main' random file read:<br><br>sam@mediabox:~$ sudo dd if=/storage/videos/Movies/Gangs\ of\ New\ York.avi<br>of=/dev/null bs=1048576 count=1024<br>1024+0 records in<br>1024+0 records out<br>1073741824 bytes (1.1 GB) copied, 26.1345 s, 41.1 MB/s<br><br>Filesystem on LV 'main' write:<br><br>sam@mediabox:~$ sudo dd of=/storage/testfile if=/dev/zero bs=1048576<br>count=1024<br>1024+0 records in<br>1024+0 records out<br>1073741824 bytes (1.1 GB) copied, 27.2666 s, 39.4 MB/s<br><br>Deleting file on 'main':<br><br>sam@mediabox:~$ time sudo rm /storage/testfile <br><br>real<span class="Apple-tab-span" style="white-space:pre"> </span>0m1.260s<br>user<span class="Apple-tab-span" style="white-space:pre"> </span>0m0.008s<br>sys<span class="Apple-tab-span" style="white-space:pre"> </span>0m1.084s<br><br>Filesystem on LV 'tv' write:<br><br>sam@mediabox:~$ sudo dd of=/tv/testfile if=/dev/zero bs=1048576<br>count=10241024+0 records in<br>1024+0 records out<br>1073741824 bytes (1.1 GB) copied, 14.4985 s, 74.1 MB/s<br><br>Deleting file on 'tv':<br><br>sam@mediabox:~$ time sudo rm /tv/testfile<br><br>real<span class="Apple-tab-span" style="white-space:pre"> </span>0m0.653s<br>user<span class="Apple-tab-span" style="white-space:pre"> </span>0m0.000s<br>sys<span class="Apple-tab-span" style="white-space:pre"> </span>0m0.488s<br><br>Filesystem on LV 'tv' random file read:<br><br>sam@mediabox:~$ sudo dd if=/tv/2920_20090514175900.mpg of=/dev/null<br>bs=1048576 count=1024<br>1024+0 records in<br>1024+0 records out<br>1073741824 bytes (1.1 GB) copied, 13.2303 s, 81.2 MB/s<br><br><br>Conclusion: Inconclusive. The last test showed a higher throughput on the<br>XFS filesystem than on the underlying LV container. I must admit, this is<br>not a very controlled test and the backend may have been accessing other<br>parts of the array at the same time.<br><br>That said, I think its safe to assume that the RAID 5 array is a serious<br>bottleneck. Theoretical speed of the array should be close to 240MB/s. I'm<br>thinking its either the RAID 5 parity computation or serious latency issues<br>between the motherboard controller and the PCIe controller.<br><br>Others may not see having high throughput as being important. However,<br>manipulating this much data, whether it be copying, hashing, etc, can take<br>hours if not days.<br><br></div></blockquote><br></div><div>Don't expect to see 240MB/s. Your numbers are quite sane. In general I see raid 5 as 33% faster than the individual drives for a 4 drive array.</div><div><br></div><div>Even with hardware raid I seldom see things much faster.</div><div><br></div><br><div> <span class="Apple-style-span" style="border-collapse: separate; color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-align: auto; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0; "><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><div>Steven Ellis - Technical Director<br>OpenMedia Limited<br>email - <a href="mailto:steven@openmedia.co.nz">steven@openmedia.co.nz</a><br>website - <a href="http://www.openmedia.co.nz/">http://www.openmedia.co.nz</a><br></div></div></span> </div><br></body></html>