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HBA Mode vs IT Mode to connect disks for ZFS (feddit.org)

submitted 1 year ago by wasabi@feddit.org to c/selfhosted@lemmy.world

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I'm looking for a solution to connect some SAS disks to my HP dl380g9 to use with ZFS. I understand that HW RAID with ZFS is a big no-no and that a HBA in IT mode is the best solution as that is passing the disks through to the OS as-is.

Some cards can only be put into an HBA mode which also presents the disks to the OS individually, but it is not a true pass through, as far is I understood. It should be a lot better than HW Raid, though.

Picking up such a card would be the simplest solution for me. P440ar cards are available for dirt cheap, don't require a PCI slot and I can re-use the existing SAS cables without worrying that whatever a non HP card uses does not plug into into the backplane of the HP dl380g9.

Is HBA mode fine for ZFS? Or should I make sure to pick up an LSI card that supports the true IT mode?

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[–] just_another_person@lemmy.world 0 points 1 year ago (1 children)

HBA and IT are pretty much the same thing. They both present JBOD to the OS, which is what ZFS wants. The only different between HBA and IT is the latter being solely driven by what's on the card with coordination from a board handoff, for instance. It's like the stock-stock version of the chip on the coats with no custom drivers, kinda.

Either way, HBA is fine.

[–] AFaithfulNihilist@lemmy.world 0 points 1 year ago

I second this.

I have three large disk shelves, one made from a J23 CSA connected to an perc h730 in HBA mode, one made from a super micro connected to a LSI HBA card, and one that uses a repurposed DATTO unit with its original raid card flashed into IT mode.

They are all extremely reliable, handling dozens of drives and I use only ZFS for all of my bulk storage. The best part is how much faster I can replace a dead drive with ZFS than I could with any raid 5 anything. Also, ZFS is flexible enough that you can put ssds in to use for journaling and slog.

I have one machine with 192gb of RAM and I just use the ramdisk for slog. It's all streaming media so if it crashes only the buffered streams are lost, and this way I'm not burning holes through SSDs quite so quickly.