Problems expanding a Synology SHR volume on DS1821+ with a faulty SSD cache attached

I got a Synology DS1821+ array about two years ago, planning to finally cascade my other Synology units and let one or two go. So far, that has not happened, but I’m getting closer. 

DS1821plus Network Attached Storage array from Synology

Synology DS1821+, photo courtesy of Synology. Mine looks like this but with a bit more dust.

The back story of my DS1821+

This is the 8-bay model with a Ryzen V1500B 4-core 2.2GHz processor, support for virtual machines and containers, and a PCIe slot which I filled with a dual port Mellanox ConnectX-3 (CX312A) 10 Gigabit SFP+ card which came in under $100 on eBay. The expansion options include two eSATA ports (usually used for the overly expensive DX expansion units) and four USB 3 ports (one of which now has a 5-bay Terramaster JBOD attached). 

Today I could get a 40 Gigabit card for that price. In fact, I did for another project, for about $90+tax with two Mellanox cables, just last month, but I’m not sure it would work on. It’s not too hard to find one of these 10 Gigabit cards for under $50 shipped in the US. Be sure to get the dual plate or low profile version for this Synology array.

I ran it for a while with 64GB RAM (not “supported” but it works), and then swapped that out to upgrade my XPS 15 9570 laptop, putting that machine’s 32GB back into the Synology. I had a couple of 16TB MDD white label hard drives and a 256GB LiteON SSD as a cache. I know, I know, there’s NVME cache in the bottom and you can even use it as a filesystem volume now.

Here’s where something went wrong

Sometime in the past couple of updates, the SSD cache started warning that it was missing but still accessible. I ignored it, since this system doesn’t see a lot of use and I don’t really care about the cache.

Volume expansion attempt, which failed. SSD cache warning showing here as well.

Earlier this month, I got a couple more of the MDD white label drives (actually ST16000NM001G-2KK103 according to Synology Storage Manager), I was able to expand the storage pool but not the volume.

Successful storage pool expansion
The volume expansion error. No filesystem errors were discovered.

“The system could not expand Volume 1. This may be caused by file system errors. To rescue your data, please sign in to your Synology Account to submit a technical support ticket.”

Well, as I went to the Synology website to enter a ticket, I remembered the SSD issue and wondered if that caused the problem with growing the volume. 

Easier to fix than I had feared

Sure enough, removing the cache made the volume expand normally, bringing me from 93% used to 45% used. Not too bad. 


Where do we go from here?

At some point in the next month or two, I plan to get three more of these 16TB drives, pull the unused 8TB and unused 256GB SSD, and get the system maxed out. 

I’m a bit torn between using this array to replace my Chia farms, at least for a while, or merge my other two substantial Synology arrays onto it and then use one of them (maybe the DS1515+) as the Chia farm with the DX513 and an assortment of external USB drives. Flexfarmer on Docker makes it pretty easy to run Chia farming on a Synology with minimal maintenance.