[Solved] NAS Newbie Questions  



My long-standing method of backing up, using CCC to a series of HDDs daisy chained off an old Time Capsule, is finally going to get the boot, as one of the drives is reporting errors.  Now that I'm seriously considering a proper NAS, I find I have newbie questions.  I use my current setup solely for backups, and don't see that changing.

I think I'm starting in the right place, on the Synology web site.  Going through their NAS Selector, they recommend the DS218j, a two-bay setup.  I'm thinking a couple 4TB drives will be good.  We are backing up two MacBook Pros, one with a 1TB SSD, the other with a 512GB SSD and a 256GB flash drive that never leaves.

1.  Drive formatting - does the NAS handle that, or do I need to choose a format when I'm setting the system up?

2.  RAID type - I want mirrored drives; I'd assume that choice will also be made at setup?

3.  My current backups are in sparsebundles, each on a separate drive (four bundles from two MacBook Pros).  Is there any need to partition the new drives, or will the sparsebundles coexist without issue on one partition?

4.  Am I missing any major considerations?


9 Answers

My DS218j arrived, along with two 4 Tb WD Red drives. Installation and setup couldn't have been easier, and now my CCC backups are running smoothly.

The drives are RAID'ed with Synology's Hybrid RAID, which I understand to be the equivalent to RAID 1/mirrored.  I'm able to mount the sparsebundles and read the files in them, so all is good!


hey @bkmiller, I've had a NAS for about 5 years now, and at some point, I did use it as a TM backup destination. BUT, like it's Time Capsule counterpart, backing up often results in errors, or more often than not, everything will look okey dokee until you have to restore, which is what happened to me. The TM backup was corrupted and it stopped in the middle of the recovery process saying it couldn't continue. So, I went back to an external drive connected to my Macbook Pro for TM, and to another external drive for a clone. Of course, YMMV but if the ONLY thing you want to do is backup your machines, there are less expensive way to do it than a NAS.

While @bkmiller may be using Time Machine, he explicitly said he was using Carbon Copy Cloner.

Are there issues setting things up for CCC ?

You're right, my bad @dataformothingandbitsforfree.

I'm not aware of problems using CCC with sparse image on the Synology. But you wouldn't be able to boot from those either. I use CCC for my external drive so I can have a bootable drive in case my internal drive goes bad, I just don't think of using CCC on a NAS, sorry.

So the answer the original poster:

1. You'll have to choose the time of volume be it BTRFS or EXT4, on newer unit the default is  BTRFS, but the unit as to support it, you have to check if the model you're looking at has that option.

2. Again be default it should be set to SHR (Synology Hybrid RAID) which in a case of 2 disk, will be mirrored so you'll get 4TB of data storage if you put 2 X4TB.

3. you'll have ONE volume of 4TB, you can make a Shared Folder that can include all sparse bundle, or you can make 4 sparsebundles, your choice. The Shared folder will share the 4TB. You can set different permissions on each Shared Folder if you don't want other people seeing other people's sparsebundle.

4. Like I said in my previous post, I would still go with external drives for your use case though.


Does Synology have its own macOS backup solution?

On a different note, I also use CCC to backup to a basement Mac with a Drobo attached.  The Mac in the basement runs CCC and reaches out to my Macbook Pro, my Wife's 2 Macbook Pros, and my Mom's iMac 300 miles away.

CCC does fail if the target Mac is not accessible, and the most common reason it fails if mine or my Wife's Macs are VPN'ed into work blocking connections that do not originate from work.

But CCC has been very reliable otherwise.  Before that, I was using CrashPlan to the basement Mac.



Thanks for your answers.  For clarification, I do not use Time Machine, as in the past I too had regular issues backing up to networked storage.  I've been using CCC for years without issue, and somewhat regularly mount the sparsebundles and view/retrieve data.  Thus far, I've had no issues whatsoever using CCC.  I understand I don't get a bootable clone this way, but in the one instance that I needed to replace a failed SSD, I was able to install the OS from a flash drive, and then clone the data back over.

The main reason I don't back up to a locally-attached drive is simply that our laptops don't typically reside on a desk where a permanently attached drive makes sense.  In my mind, backups work best when they don't require user interaction to occur. I'm willing to forego the convenience of a bootable backup for that.

Again, I appreciate your input.


The only time my CCC backups have failed in the past have been when I fail to plug my MacBook Pro in overnight (when they run).  I get a message saying the backup failed because the Mac went to sleep.  🙂


I used to use a TimeCapsule. The processs wasn’t very reliable and I had to restart TimeMachine every month or so. I found the same when I ran TImeMachine to Synology. The problem is that TimeMachine only works to HFS file systems. Any networked device is accessed using a network file system (APS, SMB/CIFS etc.) irrespective of the file system natively runjing on the server (TimeCapsule, Synology etc). To get round this a disk image is created on the server which, when mounted presents itself as an HFS volume. This adds another layer of complexity. If the network connection should fail the open files risk corruption. In this case the open file is the whole disk image .i.e. the while TimeMachine backup!

For a long time I have been running TimeMachine to a locally attached USB Bus powered hard drive. I  can’t remeber haveing any issues with this.

TimeMachine isn’t my only “backup”. I also do a run Carbon Copy Cloner every night to a locally attached drive and once per week over internet to my brother’s Mac (and at same time he backs up to me). My files are also backed up (proper backup including versions) to  a 1TB cloud drive provided as part of my internet service provided by British Telecom. My Dcouments, Desktop and Photos are stored in iCloud. (Which doesn’t prevent them from being backed up locally).

The corruption of the disk image is perhaps less likely with HFS+ than HFS.  Nonetheless I have experienced it and with CCC too. If you don’t need a bootable CCC clone then presumably it could be written directly to the native file system of the Synology, don’t think I have ever tried it.


Glad to hear it, @bkmiller — you effectively have a mirrored setup, in that either drive could fail and the other has enough data to recover everything. But SHR is not RAID 1, and it's not "just" a mirror. Because you could take those two drives and put them in a 4-bay NAS, for example, and then add a third drive to the volume and SHR would expand to use it.


Thanks, Dave,
Which raises more questions... I understand (I think) the advantages of SHR - the ability to mix and match different size drives, and to expand across additional drives - but on the other hand, this seems to permanently tie the drives together.  Am I correct in assuming that in a traditional RAID 1 setup, either drive could be removed, mounted on a computer (assuming a compatible file system) and read independently of the other?

That is a correct assumption... in all but the rarest cases. 🙂

But... the same is effectively true of SHR with just 2 drives. One drive dies, and your Synology (or any linux PC running lvm) could successfully mount the volume. It falls into SHR's "fault tolerance" where you can recover and mount a volume if one disk fails.


@bkmiller Assuming you like the other Synology features, the next Synology purchase should be a 4-bay or Larger unit with the ability to add expansion bays.  That way you can use RAID5 where, assuming equal sized drives, only the storage capacity of 1 drive is lost to redundancy protection and you can lose 1 drive and still have all your data or RAID6, where you dedicate the equivalent of 2 drives to redundancy, but you can lose 2 drives and still have your data.

The Synology will attempt to compensate for the lost of a drive, by re-balancing the storage to get redundancy back if there is enough free space, or it will wait for you to replace the failed drive.

But drives in a RAID are generally not able to be taken out of the Synology and plugged into a disk enclosure and read by a non-Synology computer.  Even plugging the drive into another Synology would require the minimum number of drives to re-establish the RAID configuration.  The files and data are spread out across all the drives for both the redundancy and performance by not hitting just 1 drive constantly.

PS.  As of this past weekend, I'm a new Synology DS1618+ user, but I've used NAS and RAID for years, so I'm familiar with the concepts, just not all the Synology features.

I've managed to create a shared image and store Carbon Copy Cloner .sparseimage files on the share.

And I've managed to start up a web server and host my home web page that my Wife and I use.

But there is so much to explore and learn.


Thanks, @datafornothinandbitsforfree

That would be something I'd consider down the road, and I'd do so to merge my wife's and my photos and music libraries.  But for now, we have different approaches to managing both, so it's better we leave that alone... 🙂

For now, I only needed the NAS for a backup destination, to replace a stack of disks daisy-chained off an old Time Capsule.  Since one drive was reporting errors, I took the opportunity to chuck them all and set up a proper system.

I've learned a lot already in the process, so it's all good.