High Disk Utilization On The Synology NAS: Is This Bad?

If your Synology NAS seems sluggish or it hasslooowfile transfer speeds, it’s possible that your data drives are being used too much. This is known as ‘high disk utilization’, and while short bursts of high disk activity is normal, sustained high usage can cause problems – including potentially damaging your drives.

Key Points

What Causes High Disk Utilization On A Synology NAS?

Your Synology NAS hasone or more drives inside it. Whether these are hard drives or SSDs, their basic function is the same: they allow for IO (input output) of the files that they store. However ifsomethingstarts reading (or writing) on them too much, the drives will start struggling. This is called high disk utilization, and it can be caused by many different reasons:

Note:It is naturally fine to havesomehigh disk usage, because otherwise you’d never be able to take backups or run any applications on your NAS! Butsustaineddisk utilization can be a bad thing because it can overload your NAS, and cause your drives to wear out quicker (i.e. have a shorter lifespan).

Fixing High Disk Utilization On A Synology NAS

If yourNAS feels sluggish, you should firstly open up the Resource Monitor to see exactly what’s going on. The default view will be the “Overview” tab and this shows a range of useful information – which I explore in the next section. But I firstly wanted to suggest that before you worry too much about potential disk usage, you should go to the “Disk” tab and select “Utilization” on the menu. This will show you the following:

In the case above, your NAS’ drives only had a very brief period of 100%volume usage– before dropping down to normal levels. This is totally fine, and it won’t cause your NAS any problems.

However if disk utilization is staying fairly high (above 80% for many minutes), I would firstly schedule in a restart because the old ‘turn it off and back on again’ trick can really help for these problems. To do this, go into the admin panel, click the profile head icon in the top right and select “Restart”:

This will perform a graceful restart, which ensures that any running processes are shut down in a way that won’t cause them to lose data (or become corrupted). Once your NAS has restarted, wait 5-10 minutes and check the volume and disk utilization again.If it’s still high, go through the 9 sections below to try and resolve this issue.

How To Analyze The Resource Monitor

When you first launch Resource Monitor within theSynology DSM(admin panel), it will default to the overview tab of the Performance section. This is useful because it will quickly show if there are any potential problems with your RAM or CPU usage:

In the case above, my Synology’s CPU usage is fairly low (11% utilization), as is my disk usage (it’s only reading 27 Kilobytes per second – not evenmegabytes).However my RAM use is fairly high (above 80%). If this pattern occurs often, it might be that I need to upgrade theRAM inside my Synology box.

Alternatively, your CPU usage might be higher than the rest:

This might suggest that you have some CPU-intensive programs running, which you can analyze from the ‘Task Manager’.I’ll discuss this point in detail in the next section, but naturally a high CPU usage but low disk usage is usuallynota problem with your drives.

To really determine whether you have a problem with volume/drive usage, you should instead navigate to the “Disk” tab which will show you more detail about your disk utilization, but be warned that the default view (“Throughput”) isn’t always the most helpful:

This purely shows you the read and write speeds, however an M.2 SSD will havemuch higher read/write speedsthan an older HDD. So if you purely look at this graph and think“huh, the lines are quite high”, you might be misanalyzing the problem.

You should instead click the “Throughput” drop-down and select “Utilization” which will show you the overall disk utilization as a percentage – which scales relative to whatever drive type you have.

In other words, values that are consistently above 80-90% might highlight an issue because that means that your drives are consistently in use – whether you use SSDs or hard drives.

High disk usage will usually be caused by the services and processes that are running on your NAS (which I discuss in the next section), but in rare cases your drives might be failing. To rule this out, launch “Storage Manager” within DSM, then click “HDD/SDD”. Now select each drive, click “Health Info” and then “S.M.A.R.T” before selecting “Quick Test” to start the test:

Run through this process for each drive, and if any show errors or faulty drives, replace the drive. But if everything looks fine, it’s worth exploring the next most likely cause of high volume (disk) utilization – running processes.

Check The Synology Task Manager

If your drives are healthy but you still have high disk usage, switch from “Performance” to “Task Manager” on the left sidebar – and you will see the following view:

This shows you exactly what ‘services’ (features and installed packages) are running on your Synology NAS, and – crucially – how much CPU, RAM and disk they use up. In the case above, Synology’s “Antivirus Essential” package is running and using up 36% of CPU, along with a decent chunk of RAM. However it’s only reading 1.2 MB/second of data from the hard drive.

In other words, none of the services in this case are resulting in excessively high disk utilization.Naturally though, if my hard drives support up to 50 MB/second read speeds and a service is reading 45 MB/second from that drive, this would suggest that the service is the culprit.

I would then explore this service in more detail, and see if there are any settings I can tweak to reduce its disk usage. For example,Synology Photo’s media indexingcan hammer your disk, and so you might want to see if you can exclude certain folders from the indexing process.

Alternatively, the service might just be an intensive process to run – or it’s designed for higher power NASes. Synology’sVideo Surveillance Station, for example, can require more powerful hardware in your NAS – especially if you have a number of high resolution cameras. In this case, you should either move the package to a dedicated NAS or consider a RAM/disk upgrade so that it runs smoother on your PC. I discuss this point in more detail later.

Is ‘Antivirus Essential’ Running?

Synology offers a free antivirus package calledAntivirus Essentialwhich sounds really useful for safeguarding your files and keeping viruses at bay:

Unfortunately this free Synology software can really hammer your drives (especially older mechanical hard drives), resulting in high disk utilization for a long period of time. Some people argue that you don’t really need anti-virus software for your NAS because it’s fairly secure by default, but if you are concerned about viruses,McAfee’s paid-for Antivirus for Synology packageis usually more efficient than the free one from Synology. It costs around $20/£20 per year.

Alternatively, you can stick to the free Antivirus Essential package but schedule it to run at less-used times of the day. To do this, open the package, click “Scheduled Scan” on the sidebar and click “Create” to trigger a scan at a suitable time of day:

I personally forgo any antivirus software, and just ensure that I’m strict about what files I transfer to my NAS (they will always ‘go through’ the antivirus software on my Windows machines first, anyway).

Do You Need To ‘Balance’ Your Disks?

Something I haven’t discussed much yet is whether you actually do have a ‘problem’ with high disk utilization. Naturally if volume usage is constantly above 80-90%, thereisan issue – but it might not be fixable by simply reviewing your installed applications.

You might instead need to take a step back, and look at how the disks in your NAS are configured. If you have two separate volumes but 90% of your files and packages are installed on one of the volumes, you might want to rework this so that you ‘spread out’ your files and/or packages to the other volume too.

This might also require purchasing new drives, and setting up new volumes. For example in the diagram below, there is one volume that would be quite fast (the 3-drive RAID 5 SSD volume), but the WD Green one would be slower and best used for ‘backup’ type data:

In this case, I would purchase a new 480GB SSD and create two equally perfomant volumes – which will allow you to spread out your files and packages a lot better:

This is the same idea of having multiple drives on a Windows machine, and using one for your OS files, and aseparate drive for your game files. This approach means that each disk/volume has less load, and they are accessed and used in a more balanced way.

How To Do This:Moving files from one volume to anotheris fairly easy, although unfortunately youcan’t easilymove installed packages to a different volume. The simplest approach is to uninstall the package, then reinstall it – and make sure you select the new volume at this stage.

Is File Or Media Indexing Running?

Synology offers a range of indexing features to allow you to quickly find files and multimedia (audio, photos and video). Unfortunately these processes can take a long time to run (you can track them under the Task Manager), and if you never use universal search, you might wonder whether you should just kill the indexing features.

There is no GUI based option to stop Synology file/media indexing, however there are a couple of guides online:

I personally would never stop indexing altogether, especially because this might cause other bugs (or unexpected behavior) down the line, but it’s good to be aware of how you can do this if required.

Uninstall Unnecessary Packages And VMs

If you’re anything like me, you might have loads of packages installed that you intended to useat some point… but you never got around to it. These packages might be using your disk (and/or CPU and RAM), and so uninstalling them will reduce disk utilization. To uninstall a package, launch the Package Center within Synology DSM, locate the package under “Installed” or “All Packages” and click the down arrow next to “Open”, before clicking “Uninstall”:

You should also do a review of any packages that yousometimesuse, but don’t strictlyneed. Some packages – and especially virtual machine technology like Docker – can be quite resource intensive. If you can move away from these packages (and hence remove any running VMs), this can often help to reduce disk and volume usage.

Check Scheduled Tasks (Including Your Backups)

Next up, you should check whether you have any tasks scheduled to run. Launch Control Panel and then click “Task Scheduler” right at the bottom. You might want to expand out the “Next run” column to see thetimethat it’s due to run.

Checking the time is important because many scheduled tasks can run overnight when you’re asleep, so you might not see that they’re causing disk utilization problems.

You should always try and ensure that scheduled tasks run at different times, because having loads of tasks kicking off at the same time (such as 00:00am – i.e. midnight) can often cause your Synology NAS to struggle. Simply moving them to different times (i.e. one at 1am, another at 2am, and another at 3am) can help to avoid disk utilization problems.

Finally, you should review your backup jobs (you do keep backups, right?). While many people use Hyper Backup to perform their backups, there area range of other backup optionsand some might run more efficiently than Hyper Backup.So if you frequently see your backup job in Task Manager using a lot of risk usage, you might want to experiment with the other backup packages to see if they run better.

Check The Volume Settings (Like File Compression)

When you first setup a volume on your NAS, it’s easy to get carried away by all the cool sounding options (yes I think that“data checksum for advanced data integrity”is cool, sue me!).

However some of these options can slow down your NAS, because they require more computational power to run. For example, the notes for“Enable file compression”says:

Enabling file compression will result in lower system performance of the shared folder. We recommend enabling this option on those shared folders storing cold data.

So you should double check your shared folder and volume settings, in-case you might have enabled a setting that causes more disk usage than you were anticipating. You can check the volume settings under the Control Panel by clicking on “Shared Folder” and then selecting each volume and clicking “Edit”.

There are a couple of other settings to check under the Storage Manager, including the RAID resync approach (under Global Settings). It’s usually worth selecting“Lower the impact on overall system performance”option here, otherwise any RAID volumes will run slower than you might like.

Don’t Exceed 80% Disk Space Usage

As a final tip, you usually shouldn’t exceed 80% volume/disk usage on your NAS. You can check this by opening Storage Manager and looking at each volume’s usage:

Your NAS will need enough free space to create temporary files for a variety of purposes (including log files and for scheduled jobs). If you have insufficient free disk space, your NAS will run into problems and this could manifest itself as high disk usage.

Note:while the usual rule of thumb is to use less than 80% of storage space, this will naturally vary depending on your drive/volume sizes. You should definitely stick to this rule if you only have 100GB drives, but if you have 200TB drives, it would be silly to say“I’m going to keep 40,000GB [20% of 200TB] spare for temporary files”. Even 1-2% of free space should be enough if you have 200TB drives!

How To Prevent Overly High Utilization In The Future

Hopefully by now you have taken a deep dive into your NAS and fixed your high disk utilization problems. Going forward, I wanted to give a few quick tips so that you hopefully don’t hit into the same issues going forward:

Related Reading:Synology NAS: Turn It Off At Night, Or Run It 24/7 (All The Time)?

Tristan has been interested in computer hardware and software since he was 10 years old. He has built loads of computers over the years, along with installing, modifying and writing software (he’s a backend software developer ‘by trade’).Tristan also has an academic background in technology (in Math and Computer Science), so he enjoys drilling into the deeper aspects of technology.Tristan is also an avid PC gamer, with FFX and Rocket League being his favorite games.