SSDs Cache for DS720+ worth it?

[badtoast]

Good day all -

I am a new home-user of a Synology DS720+ and I am reaching out in hopes to find recommendations about configuring SSD cache.

My current set-up and use: (2) 4TB HDD Seagate IronWolf drives in RAID1 and (1) Seagate IronWolf 510 M.2 SSD configured as read-only cache. The NAS is connected over a gigabit network. Currently, I use the NAS as a media server (DSVideo, music, SynologyDrive, Cal/CardDAV) and there are only 3 users of the the NAS (2 locally, 1 remotely). I have just started dabbling with Docker and VMs - My first docker container is Bitwarden_rs and I intend on setting up a pi-hole container as well. I may add a web server in the future as well. As for VMs, I'm not certain what my use case will look like, but I am currently in my second semester in a Cybersecurity program and I am told that VMs will be a necessary tool.

So on to my question: is it worth getting a second M.2 SSD for my use case? My Cache Advisor is currently showing: 97MB Hot, 64GB Warm, 447GB Cold, 169GB Archived. The Used capacity is currently only at 5.67GB. This seems like such an insignificant amount that adding another SSD would be way over-kill. Would read-write cache improve any of the services I mentioned? I have read that read-write cache is a little more risky due to potential data loss and it would be best implemented with a UPS, which I don't have. Any thoughts, suggestions, or questions very much welcomed!

 

[Shadow]

Congrats on the purchase of your NAS and welcome to this forum.

So on to my question: is it worth getting a second M.2 SSD for my use case?

You're first SSD sounds already quite decent to me. I'm not sure myself if you would gain anything with a 2nd SSD cache as it stand right now...

Would read-write cache improve any of the services I mentioned?

You're VM's might definitely like it. VM's will be asking alot of HDD activity when booting for example and are obviously more 'heavy' then most Docker containers. But it also depends, just like Dockers containers, what you do with the VM's.

The best example I can think of where SSD cache makes a great overall advantage for the performance of the system is an (very?) active Maria/MySQL database, which can also run in a Docker container or is shipped along with a Docker image to run an application/service. Because that database would be doing many read/write activity on a disk.

I have read that read-write cache is a little more risky due to potential data loss and it would be best implemented with a UPS, which I don't have.

That may be correct. A sudden power-loss during a moment a NAS is still processing data from the SSD cache to the regular disks can be catastrophic for that piece of data.

 

[Rusty]

R/w would be beneficial for VM and working with apps that multiple users are accessing (like drive with a large number of smaller files).

Regarding media it won’t be beneficial unless you are running media platform on the nas on top of pure media storage.

So all in all it will have benefits but you can add it later on at any point

 

[badtoast]

Thank you for your quick and thorough response @Shadow and @Rusty. Much appreciated!

Regarding the 'write' side of R/W cache, how long does data stay on the cache before it is actually written to the HDD? If, for instance, I am performing a backup of my laptops, how can I be assured that it is written to the HDD rather than sitting on the write cache? I'm just trying to understand how risky it actually is, in my case, to install

I think I'll work with what I have for now and consider adding when a performance improvement feels necessary. In truth, my NAS has performed impeccably as it is. I'm a very happy customer! Also, very grateful for this very informative forum! Cheers.

 

[Rusty]

Regarding the 'write' side of R/W cache, how long does data stay on the cache before it is actually written to the HDD? If, for instance, I am performing a backup of my laptops, how can I be assured that it is written to the HDD rather than sitting on the write cache?

It will depend what you are doing on your nas or better to say what your nas is doing. I really don’t have any knowledge on when it’s writing something on the hdds but I think the main problem is power loss and this valuable seconds.

 

[EAZ1964]

A write cache ssd for backup operations is not bringing you anything. The write speed to conventional hard disks is higher than the 110MB/s that ethernet brings in the data in a continuous stream. If you want to do your VM a favour: run your nas fully on SSD.