Q: Perfomance with large library (85,000 photos)

If you can hear the external harddisk spin, it probably isn't an SSD drive and could be the reason for your slow performance.

On recommendation of an Apple specialist I moved my library (26000 photos) to an external SSD drive last month, and despite of having an older iMac without USB 3 the performance is not that much different from having it on the internal drive - about 7-8 seconds to open up photos.

The only change that I noticed and that is still puzzling me is that when I export files back to the desktop, Finder doesn't see these for a few minutes (whilst Spotlight finds them immediately). Might have nothing to do with the drive.

How much RAM do you have installed?

If you have an album with only a few photos in it selected at time of shutdown how long is the relaunch?

Have you tried to repair the library according to the instructions IN this Apple document: Repair Your Library.

Note: If you use iCloud Photo Library with Photos, this action will cause Photos to upload all your pictures again (from Fix missing or incorrect thumbnails in Photos - Apple Support).

I have about 60-70,000 pics and all applications are running from a SSD.  The Library (88GB) is on a hard drive.  It takes about 45-65 seconds to open the library which I consider pretty good.  Adobe Lightroom takes longer.  I have an i7 with 16 GB of RAM.

Now If I could just figure out how Photos decides to group and which photos to sync, I may consider user it as my primary method for managing and editing picture.

In the Photos window images are grouped by date taken (EXIF).  In the All Photos window they are sorted by date imported into the library with the newest at the bottom of the window.

If you're familiar with iPhoto the following may be of help to you:

Moments in Photos are the new Events, i.e. groupings of photos sorted by date taken.

When the iPhoto Library was first migrated to Photos there is a folder created in the sidebar titled iPhoto Events and all migrated iPhoto Events (which are now Moments) are represented by an album in that folder. To open the sidebar if it's not already open use the Option+Command+S key combination.

NOTE: It's been reported by several users that if the Event albums are moved out of the iPhoto Library folder in the sidebar they may disappear.  It's not widespread but several users have reported that issue.  Therefore, if you want to assure that you keep those Event albums don't move them outside the iPhoto Events folder.

There's a way to simulate events in Photos.

When new photos are imported into the Photos library go to the Last Import smart album, select all the photos and use the File ➙ New Album menu option or use the key combination Command+N.  Name it as desired.  It will appear just above the iPhoto Events folder where you can drag it into the iPhoto Events folder

 

When you click on the iPhoto Events folder you'll get a simulated iPhoto Events window.

Albums and smart albums can be sorted by Title, by Date with oldest first and by Date with newest first.

Tell Apple what missing features you'd like restored or new features added in Photos via Apple-Photos Feedback.

I have an album setup just to be the default view when I'm not actively using Photos so it will be the one Photos closes and opens with. 

I have a similar performance issue with 30,000 photos stored on my iMac hard drive (OS X Yosemite, 2.9Ghz processor Core i5, 16 GB memory, NVIDIA 1024 MB graphics card) . I do both Time Capsule and bootable backups and am concerned about the size of the library. Photos is sluggish to open and close. Should I be concerned that the library is too large and create a new one? Upon conversion from iPhoto I definitely lost a handful of photos (thumbnails disappeared and did everything except rebuild - heard horror stories about what could happen there). Problem I have with trying to start a new library is that we will no doubt forget to manually switch libraries back to the new one when we download - since you have to remember to hold down Option to get the choice. When I forget, i will then have mixed up importing timelines into 2 libraries. Is there a way to designate the new library as the place where new pics get dowloaded irrespective of what library I last had open? This (if even by prompt) would be such a great way for people to enjoy multiple libraries without screwing up their timeline... Any assistance would be greatly appreciated...

that we will no doubt forget to manually switch libraries back to the new one when we download -

If you double click on the library package you want to use Photos will open it.  You don't need the Option key method.  If another library is open when you double click on the library you want to use you're get this message window in Photos:

There are users with 80K and up libraries that have no problems with slowness.   However, as nolamike found out if you open the library with the Photos or All Photos window the active window it will be slower to open as there are more thumbnails that have to be rendered.

Having more than one library makes it more difficult to search for particular photos, group pictures for projects, etc.

Be sure you have a minimum of 10-15 GB of free space on your boot drive for optimal system and application performance. Never run any "cleaning" or "optimizing" apps like MacKeeper or CleanMyMac as they are considered malware around here and do more damage to the system and libraries than good.   Also antivirus software isn't needed and does slow down performance.