Help, my disk array has one dead member

[Peter Silva]

On Sun, Mar 26, 2017 at 9:20 AM, Liam Proven <lproven at gmail.com> wrote:

> On 26 March 2017 at 15:13, Peter Silva <peter at bsqt.homeip.net> wrote:
> > While the advice is good... Blaming MS licensing isn't justified.  The
> > reason firmware raid exists is because, long ago, cpus were not powerful
> > enough to take this load on in addition to other tasks, so you needed
> > processors that sat on adaptor cards to handle the load.  These days,
> there
> > is plenty of cpu, so it no longer makes any sense.
>
> No. You are confusing hardware RAID with firmware RAID.
>
> Firmware RAID does the work in the device driver, with some help from
> the BIOS. In other words, the CPU is doing the work anyway.
>
>
You're right about the confusion, but again, it isn't MS licensing. Even
giving you your definition, hardware makers sold cheaper "RAID" devices
using "firmware" implementation.  Again, no MS conspiracy required.
and yes, they were always crap.   There is a lot of crap that sells.



> > These days, "hardware RAID" is just someone else's Linux box running
> > software RAID (ok, NETAPPS are Solaris'y).  There may be a few ASICS in
> > there, but by and large, it's software.
>
> Not so. I am guessing you don't work with servers much. Hardware RAID
> is still very common, but it's not cheap. The controllers cost as much
> as a cheap PC and talk to SAS drives, not SATA.
>
>
When I think of 'hardware RAID' I'm not just thinking about controller
cards...  I was going higher in the market.   It used to be that you
connect a server to an external 'RAID-box' over SCSI, or (these days: SAS,
or FC) that had an embedded controller that spoke to the disk busses.
These days, that market is taken over by NAS and SAN devices.  We only use
internal disk for mirrored bootup devices, so yeah hardware RAID-1. For
data storage.  To me, SAN and NAS boxes are 'hardware RAID', and those you
talk to over an FC bus, or something embedded over ethernet, or over a file
share protocol.   Those "devices" run complete OS's even though you often
don't get shell access.

The point remains that the reason hardware RAID cards cost as much as a
computer is that they are computers.  In the old days, they used embedded
OS's, and all the internals are still hidden, but
I wouldn't be surprised if the "hardware RAID" cards' firmware, these days,
is an embedded Linux as well, but I admit that wasn't what I was referring
to.

anyways, the practical advice you are giving is great.  RR cards are OK as
raw access to devices, but I agree, never, ever use the RAID functionality
in them.  Much better off with something host based.

Regarding commandline complexity, Is btrfs getting to the point where you
could just use that (and forget the whole LVM/mdadm/whatever thing)
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