A home media server (Plex, Jellyfin, a NAS film/photo library) is capacity-led and read-heavy — so the best RAID maximises usable space while surviving a drive failure. Size yours in the RAID calculator.
What media workloads need
Media serving is overwhelmingly sequential reads of large files, with occasional bulk writes when you add content. It is not IOPS-heavy, so you don't need mirrors or flash for the bulk library — you need lots of cheap, resilient capacity. Large nearline HDDs in a parity array are the sweet spot.
That points to dual parity: RAID 6 or, on ZFS-based units (TrueNAS), RAIDZ2. Both keep most of your capacity, survive two failures, and stay safe during the long rebuilds big media drives require.
By drive count
Two-bay: a mirror (RAID 1) — simple and safe, half the capacity. Four-bay: RAID 6 / RAIDZ2 on large drives (two-drive resilience, good capacity); avoid single-parity RAID 5 / RAIDZ1 on 8 TB+ disks because of rebuild risk (see is RAID 5 dead?). Six-bay and up: RAID 6 / RAIDZ2, or RAID 60 / multiple RAIDZ2 vdevs for very large libraries.
ZFS adds checksums and self-healing — worth having for irreplaceable family photos. A small SSD for the OS, metadata and transcoding cache keeps the interface snappy without putting the bulk library on flash.
Don't forget the backup
RAID keeps the library online through a drive failure, but it won't save you from an accidental delete, a corrupt import or ransomware — that needs a backup. For irreplaceable photos especially, keep a second copy (another drive, cloud with immutability, or the backup tier below).
Use the calculator to compare a couple of layouts on your drives, then build it.