How To Troubleshoot Low Disk Space In A Datto Storage Array
Before we continue, do you know what a disk storage array is? A disk array is a disk storage system which contains multiple disk drives. The disk array has cache memory and advanced functionality, similar to RAID and virtualization.
Here are some examples of alerts and errors you will see in the GUI device’s web interface:
- Alert: Device filesystem is full
- Alert: Disk space critically low
- Alert: Local storage has less than (amount) available
- Error Alert: Backup skipped due to not enough free space
- Device Alert: Device is protecting more than 50% of its storage capacity
What Are The Causes of a Full Datto Storage Device?
The solution to the problem will always depend on the underlying cause(s). In no particular order, listed are the potential causes for a full storage device:
- The retention settings are too loose.
- A software conflict is causing large backups.
- The storage array capacity is too small to match the amount of data you need to protect.
- The retention policy is not enforceable because the device is not synchronizing to the Datto Cloud promptly.
- The retention policy is not enforceable because current recovery points are preventing the deletion of data from the local device.
How Does a Backup Get Skipped Due to Not Enough Free Space?
The first thing you will notice is a “Backup Skipped” error message, like this:
That is the first sign your backup got skipped. What the message is telling you is your primary storage size has reached maximum capacity on your local Datto SIRIS. To get your local backups process restarted and back on schedule, you have to free up storage space. There’s no way around it.
The backup getting skipped may be caused by numerous unseen conditions:
- The device filled up because the retention policy is set too low.
- The local Datto SIRIS is trying to protect a TPDS Size beyond 50% of its fixed retention size.
- Massive quantity changes on the machine’s volume(s) resulting in colossal recovery points.
- An app or process is running, conflicting with ShadowSnap and the Microsoft VSS Writers.
- The device triggered a new full back-up, while Shadow Protect avoids backup chain corruption.
How Do You Reclaim Space On a Full Primary Storage?
According to Datto’s Knowledge Base under their Unified Continuity Backups page, they have an easy four-step reclaim space process. Their instructions from that page are below:
1. Stop all backups on the Datto device.
- Go to the web interface of the local device.
- Under the Configure tab, select Device Settings.
- Change the Concurrent Backup Setting to 0 so storage can be accessed when space is cleared. 
2. Datto recommends local retention of 5 days of intradailies, one week of dailies, and two months of weeklies stored on the SIRIS unit. Tighten up retention settings to remove any points no longer needed.
- Go to the web interface of the local device.
- Under the Protect tab, select the Configure Agent Settings of the agent.
- Under the Basic category, click Local Backup and Retention Policy, and adjust the retention settings as needed.
- Under Advanced, click Force Retention to apply the new retention policy to the agent’s dataset. Then, return to the Protect tab and start a new backup. 
3. Manually remove recovery points that are already offsite or unnecessary points no longer needed. The most space will get cleared by starting from the oldest recovery points.
- Go to the web interface for the local device.
- Under the Protect tab, select Manage Recovery Points for the protected machine.
- You can remove individual recovery points or all of the Local data for a protected machine.
Due to the inverse chain, the size displayed by the Manage Recovery Points listing does not necessarily represent the space that will get freed by deleting it. 
4. If the device still cannot take a backup, contact Datto Technical Support. 
To prevent your Datto storage array; getting low disk space and your backups getting skipped, while putting your compliance at risk, have your device checked out and examined to be appropriately sized and frees up used storage.
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