<story><title>Hard Drive Stats for Q2 2016</title><url>https://www.backblaze.com/blog/hard-drive-failure-rates-q2-2016/</url></story><parent_chain></parent_chain><comment><author>Veratyr</author><text>Something important that I don&amp;#x27;t think many people bring up is the cost of these drives in a RAID, taking reliability into account.&lt;p&gt;When you&amp;#x27;re using this as the sole drive in a desktop machine or something like that, paying the extra for a HGST is pretty straightforward, but I see too many people passing over Seagate or WD when they intend to put them in a RAID, for &amp;quot;reliability&amp;quot;&amp;#x27;s sake, without (it seems to me) much thought into whether it&amp;#x27;s really worth it.&lt;p&gt;Sorting by $&amp;#x2F;GB for Hitachi, Seagate and WD on drives &amp;gt;= 4TB (&lt;a href=&quot;http:&amp;#x2F;&amp;#x2F;pcpartpicker.com&amp;#x2F;products&amp;#x2F;internal-hard-drive&amp;#x2F;#m=19,34,38&amp;amp;sort=a7&amp;amp;page=1&amp;amp;S=4000000,10000000&quot; rel=&quot;nofollow&quot;&gt;http:&amp;#x2F;&amp;#x2F;pcpartpicker.com&amp;#x2F;products&amp;#x2F;internal-hard-drive&amp;#x2F;#m=19,3...&lt;/a&gt;), you get:&lt;p&gt;- 4TB WD: $129&lt;p&gt;- 4TB Seagate: $114&lt;p&gt;- 4TB Hitachi (HGST): $158&lt;p&gt;So in order to get the reliability of a HGST, you&amp;#x27;re paying a 38% premium, is the extra reliability helpful in a RAID?&lt;p&gt;If you look at say a RAID6 array, aiming for usable storage of say 16TB, HGST&amp;#x27;s longest running drive (at 0.11% failure rate) would have a roughly 0.000016% chance of failing in a given year (0.0011^3 * 6 * 5 * 4) (chance of first drive failing = 6x(single), second=5x(single) etc.), assuming nobody replaced a failed disk, since you need 3 drives to fail.&lt;p&gt;Now an array of Seagate&amp;#x27;s longest running drive (2.66% failure rate) of the same size would have a chance of failure of ~0.225853% in a given year.&lt;p&gt;But, the cost of the disks in the Hitachi array would be 6x158 = $948 while the price of the disks in the Seagate array would be 6x114 = $684. For the price of the Hitachi disks you can get 8 Seagate disks.&lt;p&gt;So what happens if you just add the extra Seagate disks to the array as extra parity? Now you need 5 drive failures, giving an equation that looks like ((8 * 7 * 6 * 5 * 4 * (0.0266^5)) * 100), and a chance of failure of 0.008949%, still way higher than the Hitachi.&lt;p&gt;In the end buying Hitachi&amp;#x2F;HGST seems like the right choice anyway but I thought it interesting since I hadn&amp;#x27;t seen anyone else look at things this way.&lt;p&gt;If anyone has any problems with my math, please feel free to point it out, my stats background is pretty limited.</text></comment>
<story><title>Hard Drive Stats for Q2 2016</title><url>https://www.backblaze.com/blog/hard-drive-failure-rates-q2-2016/</url></story><parent_chain></parent_chain><comment><author>JoshGlazebrook</author><text>Looks like Hitachi (HGST) is still leading in terms of reliability. I actually have a 400GB Hitachi drive that came in my Dell Dimension 9100 a little over eleven years ago. It has a few bad sectors but it&amp;#x27;s still chugging along just fine.&lt;p&gt;Looks like it&amp;#x27;s this one: &lt;a href=&quot;http:&amp;#x2F;&amp;#x2F;www.newegg.com&amp;#x2F;Product&amp;#x2F;Product.aspx?Item=N82E16822145067&quot; rel=&quot;nofollow&quot;&gt;http:&amp;#x2F;&amp;#x2F;www.newegg.com&amp;#x2F;Product&amp;#x2F;Product.aspx?Item=N82E16822145...&lt;/a&gt;</text></comment>