[OpenIndiana-discuss] Opinions on LSI RAID vs. ZFS

[Laurent Blume]

On 09/10/13 15:37, Edward Ned Harvey (openindiana) wrote:
> In BIOS, I have the option to enable/disable SATA port 0, 1,2,3.  If
> the port is enabled and nothing connected, it throws and error during
> POST.  If something is connected, it's identified as a 1TB or
> whatever drive, and presented to the OS as c1t1d1 or whatever.  Later
> if I disconnect that drive while the OS is running, the OS still
> thinks c1t1d1 exists, but if I try to access it, I'll get an IO
> error.  If it were truly hot plug, then the OS should get a drive
> disconnected signal, and c1t1d1 should not exist anymore.  As is the
> case with a USB drive or firewire.

Solaris and descendants are not hot-swap OS's. If you want to replace a 
drive, you need to tell the system beforehand that you will remove a 
disk with cfgadm, and depending on your HBA/driver combination, tell it 
again after you put in a new disk with a combination of cfgadm/devfsadm.

Since you're not mentioning them, it sounds like you failed most 
probably because you did not follow the right step, not because it's not 
supported. You certainly cannot just pull out a disk and expect a 
replacement to work on a JBOD HBA.

Using the right commands, that worked for me for years on every 
SCSI/SATA/SAS controllers I've used, including cheap consumer ones.

> Back at that time, I looked it up, and found as you said, hot plug is
> supposedly incorporated into the SATA spec.  But it's poorly
> implemented, rarely tested, and not to be relied upon, unless you
> have another layer beneath it (such as truly hotplug capable HBA)
> which will make up for the deficiencies of the SATA hotplug.
> Basically, if your product was *intended* to be used for hotplug, and
> it advertises itself as hotplug, then it's hotplug.  But if you're
> just blindly assuming all motherboard internal built-in SATA adapters
> support it ... you're taking your data into your own hands.

Those things *are* electrically hotplug. What you're missing is that it 
also depends on the driver and the OS having the ability to deal with 
that. It's rarely automagic on that side.

Laurent