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Cheap, huge cloud backups for a Synology NAS

I’ve greatly enjoyed my Synology NAS, the DS1813+,1 for over a year, but I hadn’t found a good cloud-backup solution until now.

Arq to S3 or Glacier

Arq runs on a Mac, not on the Synology itself, and can back up any mounted file shares to Amazon S3 or Glacier.

Arq works well, but S3’s pricing can get prohibitive: priced per gigabyte, a 1 TB collection costs $30/month to host. The Reduced Redundancy option brings it down to $24/month, but that’s still significant. On the special bulk Glacier service, 1 TB is only $10/month, but Glacier is extremely clunky — simple operations can take hours or days to complete.

I used Arq with Glacier for months, but I wouldn’t recommend it. Glacier isn’t made for this, and it never lets you forget that. I’d only recommend Arq if you’re willing and able to pay for the more expensive S3 or RRS storage.

But my family’s backup set is about 4 TB (and growing). $96–120/month for RRS or S3 is simply not worth it when there are other options that aren’t priced per gigabyte.

Backblaze via iSCSI

I’ve used Backblaze to back up my Mac for years, and it’s still the option I recommend for that.2 It’s a flat $5/month fee with unlimited storage, but while it supports external drives, it won’t back up network shares. But you can trick it with iSCSI if your NAS supports it, and Synology does.

iSCSI makes networked storage appear as a raw, unformatted, locally mounted disk to your computer that you format and use however you’d like, with all of the benefits and limitations you’d expect from such an arrangement: you can’t share the volume with multiple users and the NAS can’t read the files or do anything dynamic, but it’s much faster, Spotlight works properly, and Backblaze will back it up like any other directly-connected disk.

But iSCSI is not designed for intermittent connections, like Wi-Fi — only use iSCSI over wired Ethernet. More critically, it requires special software: Macs need an $89 or $189 “initiator” kernel extension to use iSCSI disks. Third-party kernel extensions are bad news, and it’s wise to minimize your dependence on them.

I used the GlobalSAN iSCSI initiator for a few months so I could use Backblaze and browse the disk more quickly, but the initiator started causing frequent problems, disconnections, and failures. I eventually removed it and went back to normal network shares that Backblaze won’t back up.

I’ll only try iSCSI again if Apple builds native support into OS X, which seems unlikely — if they ever intended to, they probably already would have.


Unlike Arq and Backblaze, Symform runs directly on the Synology. It’s a clever idea: copies of your data are split into tiny pieces and backed up on other people’s NASes running Symform. If you contribute space to the pool, you get free backups at a 2:1 ratio.

In theory, it sounds great. In practice, that 2:1 ratio is a big deal — to back up 5 TB, I need to host 10 TB of other people’s data — and I started having doubts of the reality of relying on random people’s NASes for my data integrity. I was tempted to just make a big RAID-0 volume, then realized that my data would likely be relying on a bunch of other geeks’ RAID-0 volumes.

Those concerns aside, Symform’s fatal flaw was the upload speed. I never got Symform to upload faster than about 1.5 Mbit/s — nowhere near my 75 Mbit/s upstream capacity, and fatally slow for terabytes of data. The complexity of splitting files up between so many different people likely requires a bunch of little connections and transfers, and that’s tough to scale for high throughput, especially with the limited RAM and processing power of a NAS.


CrashPlan can run directly on the Synology or a computer, and if you run it on a computer, it’ll back up network shares (unlike Backblaze). Otherwise, it’s similar to Backblaze — unlimited space, $6/month — but has a clunkier, more resource-intensive Java app.

I’ve tried CrashPlan a number of times over the last few years, both on my computer and the Synology, and I’ve always abandoned it because of the same issue: awful upload speeds, usually well under 2 Mbit/s.

Inspired by this Alter3d post about fixing CrashPlan slowdowns, I decided to give it another try a few days ago. I installed prebuild packages on the Synology using Scott Hanselman’s guide (it used to be much harder).

Based on Alter3d’s findings, I first tried just adjusting CrashPlan’s advanced settings, still using encryption but setting de-duplication and compression to their lowest settings. This worked very well, immediately raising the upload speed to about 20–25 Mbit/s during the day and even faster at night. (I later edited the config file to tweak the values manually like Alter3d did, but it didn’t make any difference.)

So far, it’s working fantastically. I uploaded 1 TB in 3 days. It still isn’t saturating my upstream, but it’s going fast enough that it won’t be a problem.

  1. A newer DS1815+ is now available, although the differences are minor. ↩︎

  2. Disclosure: Backblaze sponsors our podcast regularly. For whatever it’s worth, I used them for years before that. ↩︎