Synology RAM upgrade. Useful or not?

[asheenlevrai]

Hi everyone

 

I am currently using a Synology DS1819+ as a file server and to host a wiki (~20 users).

The device comes equipped with 4GB of DDR4 and so far RAM usage has remained below 20% (usually around 15%). I guess this means that 1GB of RAM would be enough for what my DS does, right?

 

I now have the opportunity to replace those 1x4GB by 2x8GB. Or I could use these 2x8GB elsewhere... It doesn't seem to make any sense to add more RAM into my DS1819+ but I was told that DSM (Synology's OS) would actually use free RAM as cache to improve performance. This could be useful indeed but I'm not sure it's actually true. And even if it is true, I guess this cache is used only for writes (not reads), right?

 

What would your recommend I do with these 2x8GB of DDR4? Use it in the Synology? Use them elsewhere?

 

Thank you very much in advance for your advice.

 

Best,

-a-

 

[Skiiwee29]

<-- Moved to Servers and NAS -->

[Pixel5]

you wont benefit much from the extra RAM, that CPU will be holding you back before the RAM will.

[EscapementDog]

Also, if you aren't using the link aggregation with clients that also use link aggregation, your ram is not going to speed up transfer rates as 1 gig is a real bottle neck.  Take whatever drives you have and lookup up some benchmarks on them in MB.  Multiply by 8 and by the number of drives.  If that number is greater than 1000 then ram will not help  you.  If you are aggregating then your limit is 2000, 3000, or 4000 depending on the ports used. That same extra ram is better used on the clients so they can finish a file operation by caching it in memory while it transfer to the NAS.   

[asheenlevrai]

1 hour ago, EscapementDog said:

Also, if you aren't using the link aggregation with clients that also use link aggregation, your ram is not going to speed up transfer rates as 1 gig is a real bottle neck.  Take whatever drives you have and lookup up some benchmarks on them in MB.  Multiply by 8 and by the number of drives.  If that number is greater than 1000 then ram will not help  you.  If you are aggregating then your limit is 2000, 3000, or 4000 depending on the ports used. That same extra ram is better used on the clients so they can finish a file operation by caching it in memory while it transfer to the NAS.   

12TB Ironwolf drives : 210MBps throughput.

8 drives -> 1680MBps -> 13440Mbps

Link aggregation (4x GbE) : 4000Mbps.

 

Since 13440>4000, does it mean I would benefit from increasing the amount of RAM on the NAS?

 

Now:

12TB Ironwolf drives : ~120MBps SMB sequential read/write performance.

-> 960MBps -> 7680Mbps

Still above 4000Mbps

 

[Pixel5]

2 hours ago, asheenlevrai said:

12TB Ironwolf drives : 210MBps throughput.

8 drives -> 1680MBps -> 13440Mbps

Link aggregation (4x GbE) : 4000Mbps.

 

Since 13440>4000, does it mean I would benefit from increasing the amount of RAM on the NAS?

 

Now:

12TB Ironwolf drives : ~120MBps SMB sequential read/write performance.

-> 960MBps -> 7680Mbps

Still above 4000Mbps

 

it would still not make a difference with more RAM, also keep in mind that link aggregation does not mean you get 4000mbps in bandwidth, it means you get 4x ~1000mbps but you can only use them if you connect from 4 clients at the same time and all are using the full 1000mbps of one of the ports.

 

i learned that the hard way when i upgraded my network and learned that my synology will never transfer faster then a 1G NIC will allow unless you use the experimental multi stream SMB protocol.

That was the moment i decided to upgrade to a unit that has 10G Ethernet and learned that my requirements would cost me 2000€ when i buy a synology unit so i build my own instead of about 600€ and even got more performance now.

[asheenlevrai]

Thank you @Pixel5

[DogKnight]

That model does have the option for a 10gbe add-in card. That would be one of the better upgrades to improve performance if you have a 10gb capable network. 

[asheenlevrai]

4 hours ago, DogKnight said:

That model does have the option for a 10gbe add-in card. That would be one of the better upgrades to improve performance if you have a 10gb capable network. 

unfortunately not

Thanks

[EscapementDog]

23 hours ago, asheenlevrai said:

Since 13440>4000, does it mean I would benefit from increasing the amount of RAM on the NAS?

Unfortunately, I was trying to give you an easy answer, which you found. With that much raw bandwidth on the drives it's probably not ram. Only if the drives were slower than the maximum network bandwidth would it be worth exploring. 

 

There are weird uses where ram could help, but your first description of file transfers and wiki pages is in the sweet spot of normal NAS behavior. Maybe if the wiki page delivery is too slow, more ram could get all of the wiki into memory. But you mentioned your memory use is not maxed out, so I bet your most valuable pages in the wiki are already in there and there is plenty of room.

Do try link aggregation if you haven't, it won't effect small wiki files but it will help big transfers. Even two ports is nice. If tiny file writes are a problem (not by your description) you could turn off write through caching as long as the NAS was 1) on a UPS and 2) the UPS triggered automatic shutdown if the power goes out. I tend to do that anyway just to get some value everyday from my UPS.

To give you an idea of how little RAM matters for normal NAS operation, I was part of a team that built Linux for Western Digital consumer NAS devices. The two drive NAS devices easily saturated the 1 gig link and they only had 64MB of ram. With little ARM procs driving them. The hard drives barely warm up with such tiny demands. 

10 gig is addicting. Don't start or you will become used to scanning surplus sells on eBay looking to score cheap parts. Just saying.