On 2016-02-21 05:05, Karel Gardas wrote:
The RAID 1 discipline does not initialize the mirror upon
creation. This is by design because all sectors that are read are
written first. There is no point in wasting a lot of time syncing
random data.
I'm afraid the claim "all sectors that are read are written first" is
not generally right. E.g. disklabel <freshly created softraid>
On 2016-02-21 04:39, Constantine A. Murenin wrote:
..
Wait, I don't see the philosophical problem that you seem to be
highlighting
here ("sectors are .. written first" and "on top of the filesystem"
and
"forcing reads to be done from a certain chunk only"), what am I
missing/what is it that I don't understand?
When you do http://mdoc.su/o/newfs.8, it does not write to every
sector of the underlying partition; thus you cannot expect all sectors
to be the same.
Ah right, so at least to prepare for a RAID1C rebuild to work, at raid
setup time before disklabel/newfs, one should initialize by doing "dd
if=/dev/zero of=thelogicalraiddevice".
Also, so you mean that "patrol" even if it's in the manual is not
supported
for RAID1 nor for RAID1C nor for RAID5 or any other raid discipline.
Looking
forward to see what Marcus says & test myself & read code.
Heh, I didn't even know about this "patrol"; learn something new every
day!
A BXR.SU for "patrol" has a few MFI(4) hits across the BSDs, and
ultimately reveals the `bioc_patrol` symbol (well, a struct, really,
http://bxr.su/o/sys/dev/biovar.h#bioc_patrol), a search of which
reveals that http://bxr.su/o/sys/dev/ic/mfi.c#mfi_ioctl_patrol is the
only driver reference for this symbol.
So, I don't think you'll be getting any patrol from softraid(4); it
was added very recently by uebayasi@ on 2015-05-29, based on mfiutil
from FreeBSD (http://mdoc.su/f/mfiutil.8), and only for mfi(4).
Aha, so to sum up the findings:
* Scrub aka patrol is not supported (on the level of softraid) -
perfectly fine.
* Hot spares are supported (plug in with "bioctl -H" and plug out with
"bioctl -O")
* Rebuild is supported, and I should just figure out how (what do the
two "bioctl -R" variants do respectively, and can it be done live, and
does that mean it works like a hot-plug-in).
* Hotswap is supported if hot-plug-in is supported via "bioctl -R", so
should clarify that.
So just some minor piece of clarity left now. And also the separate SATA
controller post.
All in all I think it looks neat.
