After reading smartmontool's FAQ and a number of other tutorials/info, I
still don't quite understand why is it that smartmontool is not or can not
be used in a -software- RAID conf. I also wonder why not so many people do
if you do a search on 'smartmontools "software raid"', you will see many
people reporting "weird beaviors" and all kinds of other unwanted/unexpected
There is a question in smartmontool's FAQ, "Can I monitor disks behind RAID
controllers?", that address -RAID controllers-. However, since smartmontool
works on a hardware level and -software- RAID works on an OS level
basically, I don't see why smartmontool is not used in -software- RAID
Also, could you point me to good links and possibly books on all things hard
drives including their physicall guts, tools to deal with them, ...?
Something I notice is that some hard drives are placed vertically in some
computers and horizontally in some others, but I think (actually it could be
even proved) drives (their mechanical parts) are a lot less taxed if they
spin vertically, but I don't hear of anyone talking about these kinds of
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> After reading smartmontool's FAQ and a number of other tutorials/info, I
> still don't quite understand why is it that smartmontool is not or can not
> be used in a -software- RAID conf. I also wonder why not so many people do
Actually I'm always doing that. Software raid is using the kernel's md
devices. You can access each disk individually behind the md device as
much as you please. Ergo, zero trouble for smartmontools. In the case of
a raid1, the kernel has to write data to both disks (= twice the PCI bus
load). As a bonus, you can raid only parts of disks in any way you
please; partitions don't have to be at identical disk locations but
should still have equal size.
Hardware raid on the other hand gives you a well-endowed controller card
which has firmware on the card to handle all the disks, the raid
functions, and the array management. To the computer, this card presents
as a single hard disk. The kernel can access this new disk, but the
card's physical layout does not allow access to individual disks for the
kernel. Dead end for smartmontools, unless the card's firmware kindly
forwards smart-specific commands between the kernel and the disks. Most
cards don't, and I understand all which do need special support for this
data shuffling in smartmontools.
The there's a type of IDE controller which calls itself raid controller.
Don't you get sucked in. It's just an IDE controller card with a bit of
BIOS extension on it to create an array and make itself look like a raid
card. Often they come with a proprietory driver, which does nothing else
than the Linux md driver does anyway. It still uses the mobo CPU for the
raid computations. Promise rubbish features prominently in this
category. Treat these cards as an IDE card and turn all raid functions
off, that's its only use. Likewise, any mobo raid stuff is in this
category too. Useful as additional IDE channels only. Oh yes, no trouble
here either for smartmontools, since it's exactly the same as, say, the
primary and secondary cable on your mobo.
Volker Kuhlmann is list0570 with the domain in header
http://volker.dnsalias.net/ Please do not CC list postings to me.