Introduction

We recently upgraded our Synology NAS units from Synology’s prior model, DS1819+ to their latest model, DS1821+. This article covers the latest hardware capabilities (hint: it is a major improvement) as well as key features in their just released software upgrade of DSM 7.0 (hint: also, a huge overhaul).

For reference, I previously covered both the DS1819+ and the DS1817+ chassis including adding M2D17 M.2 SATA SSD expansion cards. So be sure to read those articles for more background on Synology’s software features including downloadable Synology and third-party applications, the file system, file sharing, synchronization & backup, and security.

In the past, I justified upgrading every time a new Synology 8-hard drive chassis was released because:

1. the resale value of used Synology 8-hard drive Diskstations on eBay is so high that you can frequently upgrade for a net cost of $100 plus fees,
2. as described below, it is trivial to migrating your hard drives from an old to a new chassis, and
3. you get the advantage of a new 3 year warranty.

This time, as I will discuss more below, the DS1821+ is markedly faster than the DS1819+ model. The speed increase makes the DS1821+ a much more compelling upgrade than previous revisions. This is especially useful if you use your Diskstation, not just for file sharing, but as an application server.

Hardware Specs

A Significantly Faster CPU

Like the DS1817+ and the DS1819+, the DS1821+ is an eight drive bay NAS. The DS1821+ has the AMD Ryzen V1500B quad-core 2.2 GHz, which is a significant upgrade over the DS1819+’s Intel “Denverton” Atom C3538 CPU. Both are 64-bit, quad-core CPUs with a hardware encryption engine (AES-NI). But, Synology claims that the DS1821+ can achieve up to 113,458 4K random read IOPS and 2312 MB/s sequential write speeds, which is 177% higher 4K random read IOPS and 76% faster sequential write speeds than the DS1819+.

In terms of hard drive connectivity: DS1821+ supports SATA III (6Gpbs). Additionally, the DS1821+ supports PCIe v3 (with a peak speed of 16Gbps).

Like the DS1819+, the DS1821 has 4GB DDR RAM and it is expandable to 32GB. However, ECC RAM is now required.

M.2 SATA SSD Expansion Is Now Built-in

With the DS1817+ and the DS1819+, it was necessary to buy a separate M.2 SATA SSD expansion card, adding cost to your NAS purchase. Now, dual M.2 SATA SSD expansion slots are built into the DS1821+, so you only need to buy (two) M.2 SSD drives. Synology provides a Cache Advisor in DSM 7.0 to determine what size cache you need. Further, in Storage Manager, you can view the cache hit rate for the past day/week/month.

Synology recommends purchasing their SNV3400 400GB M.2 NVMe SSD drives. With two drives required, at $149 each, expect to pay ~$300 more per NAS for SSD drives. Synology rates the SNV3400 at 205,000/40,000 sustained 4K random read/write IOPS. Further, they state the drives are suitable for caching workloads at up to 500 TBW.

Before taking the plunge, I ran Synology’s Cache Advisor (which takes a week to run). Because I needed less than 256GB of cache, I chose two Seagate IronWolf 510 240GB NAS SSD – M.2 PCIe drives, which cost less than half the price of the Synology models. Seagate’s drives are designed for multibay NAS RAID systems. Like Synology’s SSDs, these have a 5 year warranty. And, Samsung promises long-term reliability with 1. 8M hours MTBF.

Several considerations before you add a SSD read/write cache:

• Installing the M2. expansion cards is straightforward, provided that:
  • you know where to install the cards: on the inside left of the drive chassis
  • if you have already installed hard drives with data, you take great care to keep them in order when you remove them. You will need to remove at least four HDDs to have enough room to install the M2. expansion cards
• Synology will present a series of scary cautions including:
  • if you physically remove an SSD before migrating the data on it back to your HDDs, data loss will occur
  • if you select a RAID 1 (single redundancy), you are selecting a lower fault tolerance than your corresponding storage pool1
  • the Seagate Ironwolf was not on Synology’s 1812+ compatible M2 card list (though it is compatible with other Synology NAS models), and finally
  • you will be erasing everything on the newly added SSDs (which is fine)

What Remains the Same

Like the DS1817+ and the DS1819+, the DS1821+ supports 8 internal drive bays and 18 total drive bays including two DX517 expansion units. This translates to up to 112 TB (14 TB drive x 8) internal or 252 TB (112 TB + 14 TB drive x 10) total drive capacity. That said, there is a huge gulf between 6TB hard drives and larger capacity drives. 6TB hard disk drive pricing is sub $200 while larger quantities (10, 12, 14GB) start at $300 and cost in excess of $400 per drive. Prices also vary depending on the speed and rated reliability of the hard drive model. Bear in mind that you need to purchase the same minimum capacity hard drive for each slot in your NAS.

For our family, it is both more cost effective and more CPU-efficient to maintain two Synology DS1819+ NAS units with 6TB drives (down from three Synology DS1815+ units). Perhaps in the long term, we can consolidate to a single Synology NAS. However, this will require significant cost declines in hard drives. Further, even in a SHR with 2 disk fault tolerance configuration, today only half our data is potentially exposed to catastrophic loss because we have two NAS units.

The DS1821+ boasts 4x RJ-45 1GbE LAN ports with link aggregation and failover support. It also includes 4x USB 3.0 ports and 2x eSATA ports.

Migrating from the DS1819+ to the DS1821+

I migrated from our DS1819+ units to the DS1821+, prior to the release of DSM 7.0. So, this section describes migration using DSM 6.2.x. Because I upgraded from a Plus chassis to a chassis with an equivalent number of hard drives, literally all I needed to do was unplug the existing drives from the old chassis into the new ones. (I went to the extra trouble to swap trays though I don’t think this was necessary). (Migration from other models may require a data, rather than disk, migration, as described here).

Synology has a step-by-step explanation here. In short:

1. Ensure that your DSM operating system is up to date.
2. Backup your configuration, license keys, and PhotoStation files to your Mac or PC.
3. Transfer your hard drives, one by one in the same order, from the DS1819+ to the DS1821+ chassis.
4. Connect power and Ethernet cables. Boot up your new DS1821+ unit.
5. Go to http://find.synology.com in your web browser or download Synology Assistant to locate your new DS1821+. Because we are doing a disk transfer, select Migration.
6. Restore your configuration.2

DSM 7.0

More details coming soon after I finish testing it!

Configuration

Link Aggregation

Like with DS1817+ and the DS1819+, I configured each DS1821+ unit in a 2x bonded GigE connection (a/k/a link aggregation). With our Ubiquiti Unifi network switches, that means that each NAS unit can supply a theoretical 2 Gbps to devices on our home network. It is possible to configure each DS1821+ unit in a 4x bonded GigE connection though I don’t envision needing that much concurrent bandwidth in our home network in the near future. No additional configuration was required to migrate from my DS1819+ with link aggregation to my DS1821+ with link aggregation. However, until migration was complete, I used an additional Ethernet cable (connected to Ethernet port 4) to connect the NAS to our network.

Resources

• Synology DS1821+ Data Sheet
• Synology’s Release Notes for the DS1821 & DSM 7

Updated on April 6th, 2023