iSCSI LUN Size limit

[tonitheitgirl]

Heya,

we've just purchased a few ReadyNAS devices, all of them are the same, 4220's, 12x4TB drives (48tb, 36.43TB when raided to the default - xraid raid6), all running latest firmware 6.1.4

I've created an iSCSI lun, but I don't seem to be able to expand it to the full 36TB - only to 32.705TB.

When I go to expand the LUN, it states that the current size is 32.705TB and the maximum size is 32.705TB

Does anyone know why this might be? We looked right through the product spec and could not find anything regarding limits.

[fastfwd]

I don't own that NAS or use OS6, but the unusable space is exactly 10% of the total capacity, so I'd guess that it's being deliberately reserved... For btrfs snapshots, maybe?

[tonitheitgirl]

It's not a snapshot reserve - all disabled - and I was able to create another LUN of the difference. Looks to be a limitation of the box.

[tonitheitgirl]

Confirmed by NETGear support, operating system limit of 32TB.

[mangrove]

They didn't tell you why, specifically?

Hopefully you can solve it client-side.

[Marto731]

Tonethi,
If you do searches for 'Overhead' on the Forum here,
you will get replies re explaining, Overhead, Snapshot.

These are examples.
viewtopic.php?f=7&t=66926&p=374107&hilit=RAID+overhead#p374107

viewtopic.php?f=66&t=72933&p=405433&hilit=overhead#p405433

I think Swop space is needed for LUN, and using max 36 Tera in your case would not have been
possible, nor recommended.

Rgds Marto