RAM upgrade seen but not used? DS218+

[jucor]

Hi everyone!
I upgraded my DS218+ with an 8GB Crucial stick (after having checked compatibility on NAScompares at the time).
DSM correctly sees the 10 GB, but after using 2GB (big task) does not use the other 8GB free physical memory (still displays them as free) and instead starts swapping to disk! (right now 700+ MB in swap)
Any idea why, please?

It is possible that the extra stick is visible by DSM (as in: DSM lists 10GB of RAM), but not used? I thought that an incompatibility would just mean the stick would not be seen at all, not seen-but-not-used.

Synology datasheet said the DS218+ is expandable to 6GB, and I've gone beyond that -- so I've now orderd a 4GB stick to replace the 8GB and see if it helps. But any other idea welcome!
Thanks for any help

 

[fredbert]

Not sure what your plan was for 10GB RAM: there are plenty of stories of successful over-spec'ing from the Synology datasheet. Anyway, my DS218+ with a Crucial 4GB module* ran really well doing all the jobs I threw at it, including RAM hungry Mail Server. It usually ran at 50% usage.

*Can't find it on their site now. Part was CT4G3S186DJM.M8FNX 4GB DDR3L-1866 SODIMM 1.35V CL13

 

[jucor]

Thanks @fredbert . My plan was just that the 8GB was just a couple of quids more than the 4GB at the time, so I went for it

Yes, I'm struggling to find the right models now. Even the 4GB I believed I found this morning is not the right one, it's single-rank. I've just ordered a Syno-branded 4GB, and a Crucial CT102464BF186D 8 GB (DDR3L, 1866 MT/s, PC3-14900, SODIMM, 204-Pin) [the 8GB I currently have is 1600 MT/s, might be the problem], will see if either of those works and report here.

 

[fredbert]

My plan was just that the 8GB was just a couple of quids more than the 4GB at the time, so I went for it

It's the same reason why my LAN switch is 24 port and not 16

 

[EAZ1964]

Do you use resource monitor to check memory use?

Bit of the same here, Have 6GB memory, and 3.6 is free.
The system is designed to run in 2GB and it does, My DS620 uses some 1.6GB in cache, rest is not yet used, unless there is an app that needs it, and then it should use up more memory. I cannot imagine it will not use it if it is recognised.
The system will use disk swap as disk is not volatile, Synology does not want to risk data loss in case of power failure so in doubt it will store on disk.

 

[WST16]

Try installing the Virtual Machine Manger package and see if you can allocate some of that extra memory to a VM. You can try installing vDSM.

You can also try running a memory test using Synology's assistant then check the logs under /var/log/messages
Should show "memtest passed". You can grep for that.

 

[jucor]

Do you use resource monitor to check memory use?

Yes I do, for physical and for Swap.

Bit of the same here, Have 6GB memory, and 3.6 is free.

So at least it's using *some* of your extram RAM, if only 400 MB

The system is designed to run in 2GB and it does, My DS620 uses some 1.6GB in cache, rest is not yet used, unless there is an app that needs it, and then it should use up more memory.

I thought so too, but I have some swap actually being used, 700 MB thereof. I don't see why DMS was using the disk instead of RAM?! (see below for your further idea on the topic). And the use of cache shows that there's more memory pressure on the system with what I installed than 2GB can provide.

I cannot imagine it will not use it if it is recognised.

That's what's baffling me: how can it be recognised by DSM yet not used....

The system will use disk swap as disk is not volatile, Synology does not want to risk data loss in case of power failure so in doubt it will store on disk.

Ah, that's an interesting view. But disk-based swap *is* wiped at (re)boot, isn't it? Or has there been so advances in swap that use it as a hibernating and maintain its accessibility over reboot?

-- post merged: 16. Jun 2021 --

Try installing the Virtual Machine Manger package and see if you can allocate some of that extra memory to a VM. You can try installing vDSM.

Good idea! I've mean to try a VPN-ed vDSM for a while now, might be the occasion.

You can also try running a memory test using Synology's assistant then check the logs under /var/log/messages
Should show "memtest passed". You can grep for that.

I did not know of Synology Assistant, thank you! I'll try that when I can afford to reboot my NAS, and report.

 

[Roger]

Me too updated the memory of my DS918+ to 2x 8GB and as far as I can tell DSM is using the memory:

Also (mostly) without swapping to disk:

But then again most of the memory is used by several VMs.

I installed HyperX Impact HX316LS9IBK2/16 (2x, 8GB, DDR3L-1600 (PC3-12800), SODIMM 204). I always install memory more on the lower end of the specs, because I am more interested in stable running than getting the last bit of performance (and I never ran into trouble with this approach).

 

[technorabilia]

You could also try the free command line utility. Free does not lie.

$ free -h
              total        used        free      shared  buff/cache   available
Mem:           7.7G        644M        174M        4.0G        6.9G        2.6G
Swap:          2.0G         25M        2.0G
$

BTW
It looks like I have the exact same memory module in my DS716+...

$ sudo dmidecode -t 17 | grep -i size
        Size: 8192 MB
$ sudo dmidecode -t 17 | grep -i part
        Part Number: CT102464BF160B.C16
$

 

[johndnz]

the linux kernel will swap out un-used pages even when there’s free memory - doing so has no impact on performance and maximises free physical ram for caching.

From kernel.org: "The casual reader1 may think that with a sufficient amount of memory, swap is unnecessary but this brings us to the second reason. A significant number of the pages referenced by a process early in its life may only be used for initialisation and then never used again. It is better to swap out those pages and create more disk buffers than leave them resident and unused."

I just checked one of my 2gb boxes and can see it’s currently using 210mb of swap with 1.8gb free (1.6gb of that being used for cache)

Just had a look on one of our 8gb rackstations at work - 600mb in use, 500mb of swap used, again all but 200mb of the free physical memory allocated to cache

however you SHOULD be seeing all free memory (or at least nearly all) used for cache - ssh in and run top to verift what you’re seeing in the GUI.

 

[johndnz]

there's always the option of changing /sys/proc/vm/swapiness (which tunes swap usage) - it's set to the default 60 and if you're got a decent amount of memory AND a lot of active processes it may require changing to a lower (less agressive) value to stop needless swap activity

again from kernel.org :

swappiness: This control is used to define how aggressive the kernel will swap
memory pages. Higher values will increase aggressiveness, lower values
decrease the amount of swap. A value of 0 instructs the kernel not to
initiate swap until the amount of free and file-backed pages is less
than the high water mark in a zone.

 

[WST16]

I did not know of Synology Assistant

It’ll take a long time to test (can be over 3 hours).

 

[forkless]

Me too updated the memory of my DS918+ to 2x 8GB and as far as I can tell DSM is using the memory:
View attachment 3815

Also (mostly) without swapping to disk:
View attachment 3816

But then again most of the memory is used by several VMs.

I installed HyperX Impact HX316LS9IBK2/16 (2x, 8GB, DDR3L-1600 (PC3-12800), SODIMM 204). I always install memory more on the lower end of the specs, because I am more interested in stable running than getting the last bit of performance (and I never ran into trouble with this approach).

In case you didn't already. you may want to check your Universal Search > Preferences > Performance and untick the Utilize unused memory as database cache to improve search engine performance option.

ps. Search performance will still be adequate but you will regain quite a large chunk of the allocated memory.

 

[Roger]

In case you didn't already. you may want to check your Universal Search > Preferences > Performance and untick the Utilize unused memory as database cache to improve search engine performance option.

ps. Search performance will still be adequate but you will regain quite a large chunk of the allocated memory.

My high memory consumtion comes from several VMs that are running. Nevertheless thank you for your suggestion. I just checked and noted, that I already unticked the option somewhen in the past.

 

[forkless]

My high memory consumtion comes from several VMs that are running. Nevertheless thank you for your suggestion. I just checked and noted, that I already unticked the option somewhen in the past.

I misread your post somewhat. That said, it may help others in the future