Ive recently acquired some extremely old disk shelves that fell off the back of a truck. Thats not a euphemism btw, I literally found them on the side of the road, and judging from the dents and broken plastics they were not put there gently, but somehow they both are still fully functional. They are sufficiently ancient to where they use scsi ultra320 vhcdi ports (and sata2 speeds… and ddr1 ram…), so I was curious on how Truenas might play along with them before I bother spending like $150-200 on cables and a pcie card. The shelves are dual channel so I was wondering if Truenas would be able to take advantage of hooking up both channels or not, or if its like sas multipathing which is unsupported.
The integrated RAID controller allows you to configure installed disks in a variety of schemata.
ZFS in general does not work well with consumer or low end RAID. Those have been known the loose data on such configurations. (Enterprise SAN with it’s RAID is a different story…)
Another is:
It uses low-cost SATA drives, connecting to a computer system via the Ultra320 SCSI interface.
Using SATA drives behind another interface preventing direct access is another known problem. Similar to using USB attached SATA drives for extended periods of time. It may work fine, even years, until it does not and causes data loss.
Last, it is possible that the recent releases of TrueNAS CE simply lack support for the necessary interface cards:
Ultra320 SCSI Interface
There are times when cheap or simply given hardware is not suitable for newer uses.
Note: Using SATA drives on a SAS interface may seem like a potential problem. It is not, because SAS was specifically designed to allow SATA drives. Both as direct connects to a SAS HBA port, or via a SAS Expander port.
My man, I am entirely aware of literally all of this and plenty more (such as the fact that these shelves support jbod which will just passthrough the drives like every other enterprise disk shelf out there), I simply have two questions I would like answered:
Will truenas still play ball with scsi pcie cards and scsi enclosures?
Does truenas support multichannel scsi or does it not?
I don’t think anyone here knows. You can inspect what storage drivers are available in TrueNAS, and select a SCSI card based on that availability.
If you mean multi-pathing, no, TrueNAS removed that functionality because of people accidentally using the same disks twice, (destroying data in the process).
If you mean split bus, well, that would require 1 host SCSI bus per split bus. So if you had 2 trays, each with a split bus, then you would need 4 SCSI buses. This could be satisfied with 2 x dual SCSI bus HBAs. Or a single 4 port SCSI bus HBA, (which I don’t remember if anyone made such a card).
Now the indications are that this split SCSI bus is NOT to the disks. But it is to the builtin RAID controller, which would have 2 SCSI buses. They would be for redundant paths to the disk array. Then internally the RAID controller would have 16 SATA ports to the disks. Unless you need higher performance, a single SCSI bus on the array will likely allow all disk access.
The way some of the hardware RAID arrays work, is that you assign disks to RAID groups, and externally the host only sees the RAID group. You imply you can cause the hardware RAID controller to just pass through the disk as JBOD. This is generally NOT acceptable for reliable operation of ZFS.
Using hardware RAID JBOD mode may still cause the writes to be written to cache and or use elevator seek write methodology. ZFS was specifically written to REQUIRE in-order writes as part of it’s COW, Copy On Write strategy to enforce always consistent on disk. Using hardware RAID, even in JBOD mode, might work, and work for years, until it doesn’t. Then major data loss.
I am not trying to stop you. Just passing along what knowledge I have. (And yes, I have administered both SCSI disk trays, at home and work. As well as hardware RAID SCSI disk arrays at work.)
Guess I’ll just bite the bullet and try it out for science and report back, worst case I can just bundle the card and cable with the shelves if I sell them to recoup the cost.
