Synology Time Machine Backup – The Quota Option

DS1511+ FrontBack when I first wrote about using the Synology NAS for Time Machine backups I had decided to go with a volume dedicated to Time machine. Since then I’ve cut back it’s us, using it only for my Mac Mini. Greg recently posted a comment to that post, asking about quotas, which got me thinking about alternative configurations. Especially since this coincided with me reconfiguring my DS 1511+ NAS. A dedicated time Machine volume on that was more limiting than I want. So I did some more testing and came up with a quota method on existing volumes taht aren’t dedicated to Time Machine.

Essentially, this is the problem to be solved:

  • Time Machine is designed to keep backups until a drive is full and then delete the oldest backups to free up space.
  • A share is assigned for Time Machine in the Synology DSM software. Only one share can be used across all computers.
  • Shares will use as much pace as available on the volume.
  • Quotas are user based and apply to an volume, not a share. If there are multiple shares on a volume, the quota is applied across them all for the user.

So the choices are to use a dedicated volume for backups and allow it to be filled, or use an ID dedicated to backups and set the quota on it. This article covers the latter option.

Requirements & Notes

I’ll need an ID dedicated to Time Machine backups. A ID could be shared across Macs but I decided to go with individual IDs per Mac. This gives me slightly more flexibility in the way I manage quotas.

I found that Time Machine does not handle quota changes. It appears that when Time Machine first attaches to a drive (or share) it registers how big the drive is. Even though Time Machine saw the extra space after a quota increase (in it’s space available display) when it got down to the actual backup it based the backup on the old quota. For example, I had to delete the Time machine backup for the Mac and have it start over after I increased the 1 GB quota I used for testing. . I suppose I could have copied the old files for safe keeping, but this was just testing. This isn’t much different than a physical disk, but it would have been nice to have the flexibility.

This works on my DS 212J and DS1511+ NASs. Both are running DSM 4.0-2219, which is the latest version at this time. My Macs are running OS X 10.7.3 Lion, also the most recent version.


The setup process includes creating the share, enabling TIme Machine in DSM, creating the IDs in DSM and finally, setting up Time Machine on the Macs. Click on any of the images in this section to see them full size.

Create the Share

First off I’ll set up the Time Machine shared folder using the DSM control panel.

Screenshot of the Synology Control Panel

Create the shared folder.

Enable Share

Don’t setup any privileges yet so just click OK on the privileges screen without enabling any access. I don’t want any of the regular IDs to have any access to this share.

Create the User(s)

This is also done through the Synology DSM Control Panel.


Create a new user


Fill in the user information


Click OK on the groups screen and allow the user to be a member of the Users group. (For this purpose I don’t think it needs to be a member of any group, but I’ve yet to test it and I’m not all that concerned with security for this ID.)


Give the user access to the Time Machine share.


Set the quota for the volume that the Time Machine folder is on. This is how much space the ID can use for Time Machine.


There’s no need for additional privileges so I disable access to the applications.


After confirming the setup I’m done. I repeat the steps for a second ID, setting a 500GB quota for the ID MBUser.

Enable Time Machine on the Synology NAS

Time Machine is enabled through the DSM Control Panel


Enable the Mac File Service and select the Time Machine shared folder.


Click Apply and acknowledge the warning that network services will restart.

Setting Up Time Machine on the Mac

This is a normal Time Machine configuration, but I’ll run through it.

Open Time Machine Preferences.


Click the Select Disk button. The Synology NAS should appear in the available drives. I the screenshot below both my test and production Synology NAS’s are shown. Normally you’d see just one Synology NAS listed.


You’ll be prompted to provide an ID/password. Enter in the ID created above.


Time Machine will begin a countdown to start a backup. You can make any exclusions at this time. (For example, I exclude my virtual machines directory on my MacBook Air so I don’t back them up over wireless.) You’ll also see the amount of free space. In this example, the volume the share is on is 10TB in size so it is seeing the 250 GB quota.



Further Testing & Wrapping Up

I’ve only used this configuration a short time so it’s long term viability is still undetermined.  I have setup my test server with smaller quotas and on a smaller volume so I can see what happens when the quota is reached. I also want to see what will happen when other files consume so much of the volume that there’s less than the quota available to Time Machine, I’ll come back and update this post when I have that information.

So far I haven’t had any problems connecting to shares using my regular ID from the Macs that have Synology Time Machine configured.

I’m still skeptical of using Wireless to backup Time Machine, which is unrelated to Synology. I have a pretty reliable wireless connection but there’s still the relatively slow speed. If I’m doing other work that makes heavy use of wireless the Time Machine backup could impact that. I’m going to leave it setup, at least until it causes a problem. I’ll come back and update this post if it does and I’ll include a status in my next Trail Log.

Anyone else have any experience using Time Machine servers, Time Capsule, Synology or others?

Synology File Storage Notes

DS1511+ Front

DS1511+ FrontI spent some time this weekend playing around with my Synology 1511+ NAS and various file functions. I decided to start collecting some of the less obvious (at least to me) things I learned. My setup is a Synology DS1511+ with two DX510 expansion units.

  • RAID array rebuilds are a low priority background task and have no noticeable impact on performance.
    Example: I was doing a RAID rebuild while at the same time running robocopy to copy about 5.5 TB from the drive array to a different array. The RAID array rebuild progressed less than 10% during the first day and a half while the copy (and other activity) were running. Once the copy was done and the drive wasn’t being used the remaining rebuild took less than 6 hours.
  • DSM seems to queue even unrelated drive/volume changes and does them serially.
    Example: During an array rebuild on one disk group I expanded a iSCSI LUN on a volume configured on a second disk group. Despite not being on the same drives and seemingly unrelated I had to wait for the array rebuild to finish before the LUN expansion happened. It could be initiated, but stayed in a “waiting” state until the raid rebuild was done.
  • The root and swap file systems (basically the OS) are on the DS1511+ drives but not part of the file system volume that’s on the drives. They appear to be spread across all drives.
    Example: Removing the volume that’s on the drives still lets the system boot. Removing one of the drives, even with no volumes on it, results in messages that the root and swap volumes have entered a degraded state. Popping in a new drive results in eventual message that the consistency check on both volumes is done. At this point an additional drive can be removed and replaced without a negative impact (but another degrade/consistency check).
  • DSM did not like it when I removed Volume 1 from the DSM 1511+. I was a bit concerned it wouldn’t let me remove the only volume in the unit, but it did so without any warning messages before I told it to go ahead and do it (I had moved everything off it – it does warn if a share, service or package would be impacted). But during the removal I got a message that the volume had crashed. There’s not much to do with a crashed volume so I rebooted. The volume was gone after the reboot and everything seems fine.
  • Disk Group and Volume names are system generated and cannot be changed (at least through the GUI). Just something to keep in kind if you try to organize disk groups. When I deleted Disk Group 1 I still had disk groups 2 & 3. When I went to recreate the disk group it was named Disk Group 4 and I had no disk group 1. (This might be related to the crash when I removed the original Volume 1 but it does seem completely gone.) [Updated Apr. 29th: When I created a disk group and volume about a week later they both slotted in as Volume 1 and Disk Group 1 respectively. I also did a firmware upgrade before doing the volume and group creation.

That was it for this weekend’s explorations. I did come up with a couple of questions I want to explore in the future:

    1. Can the disk groups be moved between the expansion bays (for example, if a expansion bay fails can it be moved to a new one)? A similar question is can the drives be moved to a new NAS and preserve the data, but I don’t have the hardware to check that out.
    2. If DSM 4 is re-installed, will the disk groups and anything installed on them remain after the installation? According to Synology this can be done, although with the loss of configuration data for some Synology DSM services that are kept in it’s internal database.
    3. After swapping out the fourth drive (out of 5) I never got the consistency check finished messages for the root and swap. Maybe it did a consistency check on one of the reboots and never logged it. Maybe I’ll crash the system when I pull that fifth disk. [Apr.29th: Pulling the drive went fine, see below.]

I suspect that the DS1511+ will crash when I pull that 5th drive for replacement. Synology’s solution involves having their tech support remote in the check/repair the file system. Instead I’ll make sure I have an extra backup then go for it. Might as well test how this thing holds up. Once I know I’ll update this article.

[Updated Apr. 29th]

I was wrong in point #3. Everything was fine when I pulled that 5th drive. I got the degraded error message for root and swap but everything worked, even with a reboot. Eventually I received the message that the rebuild was complete. So it looks like those earlier consistency check complete messages were just lost in the ether.