# What a target needs

> The iSCSI features BeamDisk needs from a target: SendTargets discovery, an allowed initiator name, CHAP with MD5, persistent reservations, a disk size in whole MiB or GiB, and optionally UNMAP and CRC32C digests.

BeamDisk speaks standard iSCSI. It's tested with TrueNAS and with Linux targets (LIO / targetcli). Any target should provide:

| Feature | Why |
|---|---|
| **SendTargets discovery** | Add Disk finds targets and disks from the server's address. |
| **Access by initiator name** | The target must allow this Mac's initiator name. Targets usually hide disks from initiators they don't allow. |
| **CHAP with MD5** (optional) | BeamDisk supports None, CHAP and mutual CHAP, with the standard MD5 algorithm. It uses the same user and secret for discovery and for the target. |
| **SCSI persistent reservations** (SPC-3) | How BeamDisk gives a disk to [one Mac at a time](https://beamdisk.app/docs/disks/exclusive-access/). Without them, a disk connects unprotected. |
| **A size in whole MiB or GiB** | Other sizes may not connect: BeamDisk then says **Its size isn't a multiple of 16 KiB.** Change the size on the server. |
| **512-byte or 4 KiB sectors** | Both work. 512-byte sectors keep a disk readable by other systems' initiators: see [File systems](https://beamdisk.app/docs/disks/file-systems/). |
| **Thin provisioning and UNMAP** (optional) | Lets BeamDisk [give free space back](https://beamdisk.app/docs/disks/free-space/) to the server. |
| **CRC32C digests** (optional) | Used when the target asks for them, or as set in Settings → Connection. |

BeamDisk opens one session per target, as the initiators in Windows and Linux do, so a target that allows one session per initiator needs no changes. The disks on one target share it.

Running a target we haven't tested? [Tell us](https://beamdisk.app/docs/troubleshooting/get-help/) how it goes.