Re: Homebuilt NAS Advice
On 8/7/2020 10:48 AM, Stefan Monnier wrote:
Extra space taken, extra power used 24/7 (which in turn requires an
extra plug because the poor BananaPi can't provide all that power),
Now it is my turn to ask, "Seriously?"
[ See, our use cases *are* very different. ]
Yes, in my experience Banana Pis quickly become unreliable if you push
their power system a bit (e.g. I've had no end of problems with it until
I finally found a good enough USB cable to provide power).
No, I am talking about "Extra space taken, extra power used 24/7". An
external device just does not use that much power or take a lot of space.
Extra failures (more hardware => more failures), ...
More failures on average, but far less serious and costly ones.
In terms of monetary cost, the RAID solution is definitely on the "more
expensive" side (at least overall, and I can't see why it would be
cheaper "on the spot" when a you need to replace a failing drive).
RAID originally stood for "Redundant Array of Inexpensive Disks".
Folks now tend to use "Redundant Array of Independent Disks", in part
because many RAID arrays use very expensive disks, but also because the
delta in cost between large, fast disks and smaller, slower disks is no
longer all that high. Nonetheless, it is still true a collection of
smaller disks can be less expensive than a large disk, especially if one
already has some smaller disks laying around.
RAID is basically an insurance.
Not entirely. A RAID 5 or RAID 6 array is far, far faster than
a single hard drive.
Right, RAID-over-USB is of course going to blow my SSD-over-SATA out of
the water by a wide margin (not!).
On the Banana Pi it can.
I'm not sure what makes you think so. In terms of bandwidth USB2 limits
With some exceptions, the Pi boards use micro SD cards. They are
slower than an external drive. I have confirmed that.
It is also much larger than a single hard drive, sometimes at
less expense than a single large hard drive.
That's great if you happen to be in that spot, but that's not my case.
What spot? You mentioned cost. For many configurations, 4 small
drives are cheaper than 1 large one.
My space needs are sufficiently low that I don't need to buy an
expensive large drive. The drive with the lowest cost in terms of "GB
per $" is plenty for my needs.
This thread is about a NAS, remember? By definition it is a repository
of data.
I don't think it can because you then have to sync the external drive
with two different internal drives and that seems to be asking for a lot
of trouble because of the need to keep your different systems 100% in-sync.
That is very simple to accomplish. A boot script will do it.
And if I keep my home partition in it, the "presto" comes with the
footnote "after you logout and log back in" (fun!)
You lost me. Why log out?
In my experience unplugging a USB disk while it's mounted is a recipe
for hangs and replugging it will not always bring the partition back to life.
Why do that? Boot the machine with the array attached. In any case,
we are talking about an available option, here. It exists with an
external device. It does not without. One chooses to avail one's self
of an available option, or not. Without the option, there is no choice.
I definitely prefer options.
but if I don't keep my home partition on it, then my home partition
is again not protects by RAID at which point I'm starting to wonder
what I would put on that RAID.
Data, but then I definitely recommend putting /home on the external
array, so the question is a bit moot.
I don't have other data than /home on my laptop.
Again, I remind you this thread is about a NAS.
It's really not any different logically than an external drive,
except it is faster, larger, and more robust.
It's no different, indeed, except a bit more expensive and bigger.
Well, OK. How much is down-time worth?
What down time?
You mean the time to walk over and grab my hot spare laptop?
Which does not have the information on the failed laptop. If that
information is at all important, it constitutes downtime to recover it.
For a NAS, that can be pretty big.
If you consider the cost of the downtime associated with
a failed system to be trivial, then that aspect is
not important.
That's exactly my point.
Does that relate well to the thread? To other people setting up a NAS?
Even more so when that downtime only happens once every 10 years or so
(my rate so far is a bit lower than that, but let's assume that a drive
of mine will fail tomorrow).
I had to deal with six failed drives last month. While higher than
most months, it isn't a record, either. My downtime? Zero. Compare
that to a Windows system which suffered a catastrophic failure of its
RAID array a few months ago. I am still recovering from that.
But more importantly: there's a reason why I'm not using an external
drive at all in the first place.
I am sure there is. Do you admit that external drives are extremely
popular? Literally millions of them are sold every year.
Yes, and so were floppys and optical drives.
That's argumentative. They serve a very real purpose.
No, I'm just saying that RAID will save me from this trouble once every
10 years, but other things will still cause me to lose some of my work
several times a year, so the gain of RAID is a drop in the ocean.
All I can say as a 40 year veteran in this industry is that is not my
experience.
As I said, downtime is minimal because I have other machines I can use
"on the spot".
Again, not with the data from the failed system.
As for time to rebuild a system, it's a matter of connecting the new
drive to my running system (via an external enclosure) to clone the
100GB or so of my root+home and then put the drive into its
final destination.
Yet again, missing any data on the old machine. If that data is not
important, then fine, although it begs the question, "Why have a
computer at all?" If a backup exists, then the data can be recovered
onto the new system, but that takes *TIME*. Any data not on a backup
must be manually recovered by reproducing the original work, and that
can really take *TIME*. In my case, sometimes months. I am talking
about a real-world scenario, here, which actually happened, not a
hypothetical. I am also talking about five digits in terms of the cost.
Not fundamentally very different from plugging it into the machine and
waiting for the RAID system to do the close. The main difference is
that the machine is temporarily unusable, but since I have other
machines it's not a significant issue.
You seem to be stuck on hardware. Machines are extremely cheap,
especially compared to the data they usually host. While firing up a
new machine does take a significant amount of time and a little money,
it is nothing compared to the loss of important data. Even if the data
is backed up, which it should be, it still takes time to restore it.
For many of us, even an hour of downtime is very expensive, and
rebuilding a machine during peak hours can be hideously costly.
It is always a pain in the ass.
Yes, I agree that RAID can be handy in some contexts.
No, it is *ESSENTIAL* whenever time and data are important.
I think part of the difference is also where we get the "reliability via
redundancy". I use my machines in such a way that none of them
are indispensable.
My machines are completely dispensable, although of course I don't like
having to pay for a new machine and the time and effort to build it.
What is not dispensable is my time and the time my clients have to wait
for me. Wasted time with a vendor can be expensive, too.
Even if the delay is not serious, it is still distressing.
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