[OpenIndiana-discuss] help needed: reinstall bootloader

[Nikola M]

On 04/18/18 12:19 AM, Timothy Coalson wrote:
> On Sat, Apr 14, 2018 at 1:43 AM, Nikola M <minikola at gmail.com> wrote:
>
>> And also there is the question weather Hard disk cache is turned on if ZFS
>> uses partition and not the whole drive. Previoiusly, Hard disk caching used
>> to be turned OFF if ZFS is on partition and not on the whole drive, for UFS
>> compatibility.
>> Don't know how it is now nor how to explicitlycheck/turn ON Hard disk
>> caching if ZFS pool uses partition on drive.
>>
>> previously discussed several times, long ago (though somewhat difficult to
> search for):
>
> https://www.mail-archive.com/zfs-discuss@opensolaris.org/msg49099.html
>
> ZFS never disables caches, and I believe they are almost always already
> enabled anyway, so you can forget this concern.  From what I understand
> from reading the list, the only reason zfs has any code that touches disk
> cache settings at all is that long ago, Sun shipped some drives with the
> cache disabled by default in the firmware.  I think if you aren't using old
> drives shipped by Sun, this "whole disk" distinction doesn't matter to you
> (as long as you don't also use UFS, anyway).

I think (got confirmation on this some years ago), that Opensolaris (and 
illumos) preventively disables disk cache on all drives where partitions 
are used for ZFS, to avoid possible problem with UFS partitions on same 
drive if cache is on, and that is why disk cache is turned off if using 
partitions instead of giving the whole disk to ZFS:

So question is for present-day illumos, until then I can presume it is 
the same as before for cache/partition thing, so needing more recent 
info on this.
Unlike explanation about shipped drives, I got explanation about UFS 
getting garbled if disk cache is On and using partitions.