Drive and RAID configuration questions

[vitahondon]

I am really confused about some drive / raid configurations I've seen people have with their homelab servers. Both virtualization servers and NAS servers. Below I put some examples.
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Configuration 1: Variety of different drives on "ONE!" HBA card.
HBA: SAS-9211-8i IT mode
Drives: 4 Seagate Ironwolf 6TB HDDs / 2 Seagate Ironwolf 1TB SSDs
All drives connected through the 1 HBA controller. The 4 HDDs are connected via 1 SAS to SATA 8087 cable and the SSDs using the second cable. Is this configuration possible? If no, how are u guys setting up caches for plex on SSDs? Are you using an entirely separate HBA just for SSDs or plugging them into the board and setting them up with software raid?
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Configuration 2: Installation of TrueNAS or base OS (any server really), To RAID or Not to RAID?
HBA: SAS-9211-8i IT mode
Drives: 4 Seagate Ironwolf 6TB HDDs / 2 Kingston 240GB SSDs
All HDDs connected through the HBA controller. How are you all installing the OS and where are you booting from? Do you have your boot drives directly connected to the board? For people who have the OS in a RAID array: Are you software raiding that array or, like the above question, are you using two HBA controllers?

 

[Jason Antes]

Yes, those configs are possible to have on the hardware. IT mode just means you see every drive and can't hardware RAID with the HBA. It's desirable for software implementations of RAID or JBOD systems as the HBA's logic and cache don't get in the way. These were also used with disk shelves that had their own controller built in to do those functions (such as HP's vraid implementation on certain MSA's). Size of drives doesn't really matter, mostly. The interface only matters if the HBA can't address both SAS and SATA at the same time. Usually not an issue for enterprise HBA's.

For the question of RAID on the OS drives, if you wanted to do RAID in hardware you'd have to have a 2nd HBA that was not in IT mode.