If your array was configured with 1 disk fault tolerance, might still be possible to recover data. But you probly won't be able to rebuild the array since it will be in a degraded state & DSM messed up.
If data is important, I would try
-Boot into a Ubuntu live USB & try to mount the array as read only. https://kb.synology.com/en-br/DSM/tutorial/How_can_I_recover_data_from_my_DiskStation_using_a_PC
-If data is accessible, get a new hard drive that can hold all of the data, or at least your most important stuff.
-Copy data to new drive
-Reinstall Xpenology/DSM, setup & format from scratch
-Manually recreate shares & copy data back from new drive.