If Eagle shows the notification "Bad Library Storage performance", this could mean the device where you store the library has insufficient read speed, so Eagle is unable to display images at the utmost speed.

Should you encounter the situation, please try the following troubleshooting steps:

Before trying the solution below, you could try download Eagle's latest version , the issue you've encountered could've been fixed in the new version.

Check if you're using a third party app to access an NTFS formatted disk
Based on our dev teams test, the random read performance will be hindered significantly whether you're using Tuxera NTFS or Paragon NTFS apps; If possible, we still recommend you to store data on a disk with compatible formats. (APFS / HFS+)
Check if your device is plugged in a USB 3.0 port
If you use external storage, the reason being to this could be the storage is plugged in a USB 2.0 port, or there is a problem on the USB hub you use, resulting in low performances. Please switch ports or leave your hubs to see if the performance returns to normal.
Check the disk performance
Check the disk performance with software like Blackmagic Disk Speed Test (MacOS) or CrystalDiskMark (Windows). The recommended read/write speed is no lower than 50MB/s
Upgrade to faster devices
If possible, consider upgrading your hardware to allow Eagle to run in the best performance. The recommended read/write speed is no lower than 50MB/s

To secure a best Eagle experience, we recommend you to store the library on the storage with better performance.

Eagle showed "bad library storage performance", how do I fix it?