Synology NAS, low disk usage, 100% volume usage

agw_01 · 9 Oct 2019 at 15:06

Hi guys,

Got a bit of a weird one here. I've had my Synology DS212j for years and started noticing poor performance browisng file shares and accessing the GUI about 3 months ago.

It's running a pair of 3TB WD Reds as single drives and it is literally only used for Surveillance Station (3 cameras) and a periodic rsync target for a FreeNAS box.

Initially, I noticed that the volume use of disk 1 was pinned at 100% for hours and hours on end even though the actual disk utilisation was very low. More recently, the volume of both disks was sitting at 100% but again, with very low disk utilisation. CPU and memory usage are also very low.

Restarting the box usually resolves it temporarily and I've also tried updating to the latest version of DSM. It was behaving for a few days but is now back to its old tricks.

Last night I wiped both drives and performed a clean installation of DSM. I haven't touched it since, just got home from work and again both volumes are pinned at 100%. Disk usage is 0 and this is backed by the steady HDD lights on the front of the unit. Volume read/write speed is also 0 as are the number of reads/writes per second. SMART values for both drives are fine.

I'm guessing this is some sort of DSM bug, it's just a little odd that it has been absolutely fine until a few months ago. DSM hadn't been updated prior to the issue occuring.

Thought I'd ask if anyone has experienced similar before I start replacing drives and reverting to earlier versions of DSM.

Very strange!

sja360 · 9 Oct 2019 at 21:00

I've got the same synology unit, only thing I'd say is I haven't got two drives, perhaps it's something related to the surveillance side? Try adjusting settings or something to see if it's still crazy.

agw_01 · 9 Oct 2019 at 21:38

The odd thing is, it's only started doing it recently and nothing has changed. Same drives, same DSM installation. I just noticed it running slow one day.

I thought I'd cracked it before, disabled all the services (SMB etc), disabled the universal search tool (SynoFinder). Restarted the NAS and both volumes were back down to 0%. Started enabling SMB, SSH, rsync and set my cameras up on Surveillance Station. Bearing in mind the cameras are only streaming at 1.5MB/s

I mention both volumes are at 100% in the OP but the issue first started with it only affecting volume 1. Today, it's affecting volume 2. It's just very odd how the disk util is very low but volume util (there is only one volume per drive) is causing the system to slow to a crawl.

agw_01 · 9 Oct 2019 at 21:53

Surveillance Station service stopped and vol 2 still pinned at 100%. 0% disk usage.

Doesn't help the resource monitor doesn't show how much of the disk each process is using. Anyone know any command line tools that may give more information?

A quick google suggests running atop or iostat from command line but DSM doesn't seem to have those tools installed.

sja360 · 9 Oct 2019 at 22:52

I'm not totally familiar with surveillance station, but can the amount of space it uses be limited or lowered? Perhaps filling the drives up with camera files is causing the issue?

pcfarrar · 10 Oct 2019 at 08:16

How old are the Red's, does the health look good and do they both pass the SMART extended test ok?

agw_01 · 10 Oct 2019 at 21:00

Yesterday it was volume 2 that was pinned at 100% and 0% disk util so before I went to bed I removed the volume/storage pool from disk 2 leaving disk 1 on its own. Get home tonight and volume 1 is at 100%, 0% disk util. I've pulled both Reds and am reinstalling DSM onto a previously used pair of 1TB Hitatchis.

@pcfarrar, there were no SMART errors reported by the NAS and the health was fine. I've now got the Reds in another machine running a WD DLG extended test. The drives were manufacturered in 2012 and 2015.

If the Hitachis exhibit the same behaviour I think I'll try a previous version of DSM (if I can get hold of one)

ant1298 · 11 Oct 2019 at 12:35

Synology may offer support and remote in with permission to have a look. Have you tired talking to them?

agw_01 · 12 Oct 2019 at 19:32

Just an update... put in a pair of 1TB drives with a previous installation of DSM. Running absolutely fine. Updated to the latest version of DSM and absolutely no issues since. Volume utilisation is perfect. I've tested one of the WD Reds which passed the extended test and am just testing the other (2012 drive) now.

I'm a bit stumped now. A brand new install of DSM ramps up the volume util to 100% yet an old tired installation, updated to the same version runs flawlessly. The next step is try another fresh install on another 1TB drive and see if it has the same issues as the 3TB drives.

@ant1298, no I didn't even consider it with how old the DS was. Didn't expect Synology to support it.

agw_01 · 13 Oct 2019 at 12:03

The 2012 drive failed the DLG extended test on too many bad sectors, but the SMART values are ok, including reallocated sector count.

Surely if the drive has bad sectors it should have tried to reallocate them first?

agw_01 · 17 Oct 2019 at 19:54

An update...

The 2012 WD Red that failed the extended test, I did a full erase on the drive and it now passes the same extended test. 0 bad sectors reported but I'm not sure if I trust it so it will become an offline backup drive.

The DS was running quite happily for a few days with the 2x 1TB drives (low disk/vol util on both drives) so I put one of the WD Reds back in as the 2nd drive. I didn't create a volume straight away and saw 0% disk util over 12 hours. The next day I created a volume and almost as soon as the volume had been built, BAM! 100% volume util, 0% disk util again. The 1TB drive in bay 1 is working absolutely fine with expected disk/vol utilisation.

I've been using the machine for a couple of days and unlike before, haven't noticed any performance hit on the 2nd drive. CCTV footage plays back quite happily, rsync jobs are completing as expected... it's just the volume utilisation is pegged at 100% but only on the 3TB Reds. Very very strange!

Think I'll leave this one for now, my main issue was the hit on performance but using the 1TB drive as the boot/primary drive, I don't seem to experiencing that any more. Disk util is very low so it's not as though the disk itself is under a lot of load so I have no concerns about drive longevity.

Thanks all.

TheRealDax · 4 Apr 2020 at 22:59

A bit late but here is how it works.
when a volume is accessed for 5 seconds over 10 seconds this will mean 50% Utilization on a volume..
So a 100% volume usage does not necessarily mean you have a huge performance issue.
When Volume Utilization is at 100%, but Disk Utilization at 30% you have a lot of resources left to go on.
I have a 1817+ mij self with 8x 8GB WD Gold editions (Semi Raid 5 with one spare) and 6 IP cams.
Created 2 Volumes, 1 special for the Cams. sins the cams writhing directly to this volume, the volume utilization is at 100% 24/7. However Disk utilization doesn't exceed 5% when only cams are using the 1817.