iSCSI crc support

[Forza]

Hi! I'm new to FreeNAS/TrueNAS Core and I want to set up iSCSI share with a Windows client. Previously I've used LIO iSCSI on Linux. There I have used crc32c for data digests. Does TrueNAS enable crc32c for data and headers by default?

 

[Ericloewe]

You mean that the ISCSI target internally kept checksums for data integrity purposes?

Well, ZFS goes far beyond a bunch of ad-hoc CRCs thrown in with the data. All data, user and metadata alike, is checksummed to verify data integrity and guide the self-healing, when sufficient redundancy exists. You can even choose a strong cryptographic hash instead of the default fletcher checksum (mandatory for a few features like encryption and dedup, comes at some minor performance cost, and you can pick from sha256, sha512 and skein).

Check out the resources section for additional documentation, including the introduction to ZFS doc.

 

[Forza]

You mean that the ISCSI target internally kept checksums for data integrity purposes?

No, not at all. It is to ensure that the iSCSI traffic over the wire has added checksums. Nothing to do with the storage side of things.

Here is the RFC for Header and Data digest in the iSCSI protocol: https://tools.ietf.org/html/rfc3720#section-12.1

 

[Ericloewe]

Ah, that's supported in FreeBSD as far as I can tell. I don't know if you'd configure it on the target or initiator side (or both) though.

 

[Forza]

Ah, that's supported in FreeBSD as far as I can tell. I don't know if you'd configure it on the target or initiator side (or both) though.

OK. Sounds good. Would be nice to find some reference to this? As it is now, the Windows 2016 Server does not enable CRCs for Header or Data when connecting to the TrueNAS, while it does when connecting to the Ubuntu server. And as far as I can tell there is no option in the initiator to force digests.