How to hack in “Skip Sequential IO” into the DS716+

In Computing, NAS by Ross Fisher16 Comments

I take no liability for data loss! At your own risk, do backups before and before upgrading DSM!

Per previous posts, the lack of sequential skipping has been driving me MAD. Thankfully I found a way to expose the feature on the GUI for use.

Reddit member qriff said this post was stupid due to not explaining why Skip Sequential is disabled, I thought it would be apparent since the strings that enabled the feature were absent from the conf file but not everyone hacks on DSM. The reason why this feature is missing from the DS716+ is that Synology by intention or accident neglected to enable Skip Sequential IO for this model by leaving the two strings that enable it from the conf. I have called Synology and the only advice they can provide is to file a feature request at

Edit: Qriff has given me Reddit Gold and had this to say:

“Great, thanks. Just wanted to make sure that there actually where some absolute indication the option actually does something, as usually features left out don’t function on specific equipment and many are too eager to claim “hacks” working just because they have enabled a html tickbox. Be rude, you’ve earned it, as long as one also responds to the questioning. <3 Many of us have the exactly same conflicting feelings about NAS / Synology / etc.”

I never thought anyone would be reading this blog, it was more of a convoluted Evernote to store my internal ramblings. As I continue to write articles and gain a following, I will strive to write articles with an audience in mind!

SSH into your DS716+ and add these two strings:



To both the



files (right under # system options works fine). Reboot and enable the option!



I’m not going to spend another few hours recording a screencast proving that Skip Sequential IO is now working, but believe me when I say that Sequential IO is skipped on the SSD Cache and passes through to the HDDs. Yes, random IO is still cached and served from the SSD Cache. Here is one screenshot that I hope is satisfactory:




  1. Pingback: Don’t use Samsung 850 Pro SSDs in your Synology, use 840 Evos for 2-4x more speeds! | Ross Fisher's Blog

  2. Pingback: DS716+ with DS513 – SSD Cache has abysmal writes | Ross Fisher's Blog

  3. Hi Ross,

    I’m really curious about the 716+, mainly because I stumbled across your blog after seeing a video of it. I had been thinking about going with a Mac Mini with attached USB 3.0 drives as my home server. From cursory reading, I can’t get a handle on which might be better. The 716+ would be more self contained. The Mini would probably be more flexible.

    Would you mind sharing some of your insights?

    1. Author

      It depends on what you want your server to do. Off the bat, a Mac mini with a usb drive will have no redundancy such as raid 1 or 5 and will likely be limited by one disk for space unless you go with multiple shares. The good news is that if you simply want a plex media server and time machine backup destination, it should work just fine.

      Of course there isn’t a package manager for Nas related software for OS X server but last I checked, one can easily download docker to OS X to act as an application server.

      I used to work for Apple supporting OS X, OS X server is decent to an extent for basic server duties with slick GUIs to set it up. It all comes down to your personal preference.

      If you wanted a more focused home server, I’d go with a synology quad core with 2x gigabit ports. You can start with a 2 bay with 2x 6tb or 4tb drives and get the expansion unit when you need more space. It may be overkill if all you want is a home server but I’ve learned that future expansion and use ability is paramount when considering long term investments.

      Again if all you want is a server that doesn’t need to be highly available and you are fine with the disk space of a single hdd, go with the Mac mini. If you feel you need redundancy and ability to expand for future growth, go with a syno or qnap. I hear the new qnaps even have an hdmi output to double duty for a home media server!

      1. Ross,

        Thanks for the insights.

        Those new QNAPs do look interesting, but they’re missing one essential thing – you! I don’t think there’s anyone out there doing the kinda stuff you are and posting about it.

        1. Author

          Thank you Herb, that makes me feel warm and rosy inside 🙂

          I’ll eventually have a technical review of the unit along with the DX513 as soon as I fix some issues with LACP on my desktop.

  4. Really interesting choice by Synology. I wonder if they left the option out bc they viewed this as more of a streaming/media NAS and always using Sequential I/O would speed up video data transmission/transcode times since most media (video/music) is largely sequential data.

    Maybe they were more interested in posting performance numbers than giving people the option?

    Any thoughts?

    1. Author

      I still like to believe that it was a honest mistake as all other SSD enabled units have the option and it’s completely able to use the IO option. The odd duck is that they rushed out BTRFS support in this model and have a customized 5.2 version running on it while all others with BTRFS is 6.0 Beta DSM. I suppose we will see if DSM 6 has it 🙂

  5. Hi, thanks for your posts about the DS716+. I just ordered a 8GB Ram extension. About the SSDs, how did you hook them up to the DS? I’ve read that SSD caching is not supported on esata. And would be a single SSD cache only for read cache viable as well? Thanks for documenting your tinkering, it’s really helpful!

    1. Author

      Howdy Frank! I hooked up a DX513 which provided an additional 5 bays (only SATA II though). It’s critically important to place one SSD in the main unit and one in the expansion bay so you don’t loose data in case the expansion unit disconnects if you go this route.

      While the DS716+ has SSD Caching, you’ll want to be sure to enable Skip Sequential IO: as some SSDs such as the Samsung 850 Pro actually perform worse than spinning HDDs for sequential reads/writes, but are otherwise excellent for random IO.

      You are right, eSATA SSD Caching is not possible, you’ll have to have an expansion unit. Why they did this, I don’t know as it should be possible – maybe they want to sell more $500 expansion units?

  6. Hi Ross,

    First, your stuff is gold, big help for newbies like myself. Second, as a proud owner of a 716+ (came from an old school 213j plus Mac mini), I’m very happy. I use it as my plex server and basic email server it handles all my content really well. DSM 6.0 is also very nice as cloud share sync between DS’s and cloud sync between my massive Dropbox account (22tb and counting) is great. Now, I recently added the DX213 expansion on a lark with two 6tb drives and after three days of thinking, my DS is finally working the way it used to.

    I say this all to say 1) the 716+ is a great plex server and wonderful email and home server (as long as you don’t need anything too fancy) and 2) the two bay expansion comes cheap and is an easy way to double storage. And 3) with Apple TV plus plex, this passes the wife test in droves.

  7. Do you have your ssd attached to the ESATA external port, or do you have the VERY expensive extension unit?
    I hope the extension unit isn’t necessary. Any tutorial on how can that be made?


    1. Author

      Nope, they have it locked down to where you can use the eSATA port – but it’ll show up as an external drive only (meaning that SSD Caching won’t work on the eSATA port).

    1. Author

      Wow Fred! That’s one hell of a tweaks list!

      I’d love to publish this on my blog and link to you. If you’d be so kind, would you mind emailing me an article at zorrobyte (at) along with a website or other info? I get some good traffic to my little blog and would love to give you some recognition!

    2. Author

      Thank you for the comment! Awesome work! I’ve always wanted to be able to use external eSATA SSD caches 🙂

Leave a Reply