Hi TrueNAS Experts,
Short Version:
How can we change these two iSCSI parameters?
- MaxOutstandingR2T to 16 or 32
- InitialR2T to NO
Current Negotiated iSCSI Parameters:
yaml
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HeaderDigest: None
DataDigest: None
MaxRecvDataSegmentLength: 262144
MaxXmitDataSegmentLength: 262144
FirstBurstLength: 262144
MaxBurstLength: 1048576
ImmediateData: Yes
InitialR2T: Yes
MaxOutstandingR2T: 1
These settings seem suboptimal and could be improved.
Details:
Setup: oVirt KVM/QEMU hypervisor with multiple nodes using TrueNAS as storage via iSCSI.
We’re currently running TrueNAS-12.0-U2 (planning to upgrade in the next months) and want to adjust some iSCSI parameters.
- According to older documentation, TrueNAS allows MaxOutstandingR2T values between 0-255.
- InitialR2T is currently set to Yes.
- All our iSCSI connections negotiate to:
InitialR2T: Yes
MaxOutstandingR2T: 1
Even though our CentOS initiators are configured with MaxOutstandingR2T: 16
, TrueNAS seems to ignore it.
What We’ve Tried:
- Editing
/etc/ctl.conf
→ gets overwritten by database values. - Checked the TrueNAS database (
midclt call iscsi.extent.query | jq
) → No related fields found.
Example extent entry from TrueNAS:
json
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{
"id": 22,
"name": "Extent_ovirt_default_DC05",
"serial": "309c239e05b8021",
"type": "FILE",
"path": "/mnt/hdd_pool05/dataset_ovirt_DC05/Extent_File_DC05",
"filesize": "2199023256064",
"blocksize": 512,
"pblocksize": false,
"avail_threshold": null,
"comment": "",
"naa": "0x6589cfc0000007b10e94cd92661bc0c6",
"insecure_tpc": true,
"xen": false,
"rpm": "SSD",
"ro": false,
"enabled": true,
"vendor": "TrueNAS",
"disk": null,
"locked": false
}
Unfortunately, our oVirt infrastructure enforces a 512 block size.
Questions:
- Where does TrueNAS store these iSCSI negotiation parameters, and can they be modified persistently?
- Will this be configurable in TrueNAS CORE 13 via the Web UI?
- Is there any way to force MaxOutstandingR2T >1 on the TrueNAS side?
Any insights would be greatly appreciated!
Thanks in advance!
Best regards,
Raphael