5 May
2010
5 May
'10
11:02 a.m.
Hi,
On Wednesday 05 May 2010 10:39:32 Florian Faber wrote:
Imagine how plutek runs to a friends computer (or just breaks out his second
machine) when the first fails during the session?
And now imagine plutek checking ebay for days to hunt down the same hw-
controller as the one that just fried up...
Oh, most people have two or more audio-interfaces. And two or more headphones
and speaker-pairs. And two or more guitars (if they are guitar-players).
But with the disks storing the results of the work, he should be careless???
Again, the question is probably not so much the "if" or "how" but the
"how
fast" and "how pricey".
I know business you have lost raid5-systems (and all the data on it) because a
second disk broke under the stress of reconstructing a first failed disk.
But be my guest, I (*) work in a company helping such firms after disaster.
Note that we also write invoices for our work.
Have fun,
Arnold
(*) insert: almost
Don't do
hardware-raid! Neither the real nor the "soft" hardware raid
help you that much. What do you do when the controller fails?
Well, this is a
stupid advice, unless you tell plutek also to get
everything else in his studio twice. A hardware raid does all the computation for you and
just passes along
the data you need. It also eats away a lot of stress through huge
buffers. With an Areca 1280 for example, I get 3GB/s for the first
second and ~1.5GB/s sustained on a RAID6.
With software raid, you have to transfer all data twice through the
system,
No, the only place where it feeds through twice is the part memory->disk-
controller (which is pretty fast thanks to dma). Before that its just one
stream, after that its one dedicated bus per device (given this centuries
sata/sas).
you fuck up you caches,
If the linux kernel fucks up its caches when its doing its own raid, something
is _horribly_ wrong. And I doubt it is.
and the CPU has to do all the
computations. If you only have two drives, it doesn't matter that much.
What computations? - Ah, you still don't know that any [345]-raid is bad...
So it really depends on what you want to do and what
your budget is. If
you have to avoid IO stress, go and get a decent RAID controller.
If you want to avoid user-stress, do software-raid.
With a
hardware-raid you have to have a second of the same kind in stock
to get back the data on your disks. Don't even think about not having a
spare controller and buying one when yours fails.
This is only true if the on-disk
format is not specified somewhere. If
you buy cheap shit, that may be and you may have to fiddle around to
extract the data. But it can be done. The
"reduced" throughput of a software-raid is worth the ease of use. And
its not that "reduced" at all.
Again, it depends on the use case.
Oh, and use only raid1 or combinations of 0 and
1. For all the others see
http://baarf.com.
Again, it depends on the use case. As a general rule, this is
just wrong.