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Do you think it's possible to construct a table of number of drives
available versus recommended RAID level? Not that it would be an
absolute bible, but a place to start.<br>
<br>
I'm thinking<br>
2 drives -> RAID 1 (obviously)<br>
3 drives -> RAID 1 + spare<br>
4 drives -> RAID 5 + spare? RAID 6? RAID 10?<br>
5 drives -> RAID 6<br>
6+ drives -> RAID 6 + spare<br>
<br>
Fairly often, like in the 5-drive box that started this, the
question is whether a drive that will not add any storage space is
better as a hot spare or as a live, already functioning member of
the array. In the case of 3 drives, if you're really worried about
the array going down, would it be better to run a 3-way mirror
rather than a 2-way one with a hot spare? The only thing you gain
with the hot spare option is a vastly different amount of wear on
the spare since it isn't spinning until it's needed. What's more
likely: the 2nd half of a mirror failing before you get the data
copied or 2 of 3 drives failing before you buy and install a
replacement? I know statistics as well as the next guy, but these
calculations get arcane fast!<br>
<br>
On 10/02/2011 09:29 PM, Richard Nienhuis wrote:
<blockquote
cite="mid:CAJd2Bx8b+GC6t6Jy8hL32W-vxKBjd4XEsMW5W0RuqjZmmdwwnQ@mail.gmail.com"
type="cite">To bring this back to its actual application... Its a
personal music server made from scrap parts. It doesn't require 5
9's uptime of hands free operation. The most likely failure mode
of this thing is that one day a drive will fail on reboot/startup.
Hot spare isn't going to save it from a second drive failure at
startup. For its application integrity is a priority over
everything else. Downtime is a relatively inconsequential cost.
<div>
<br>
</div>
<div>Hot spare is good if you have an extra one available. In
this case the 5 drives are of better use in RAID 6 rather than
just having one sitting around. If he gets another drive at
some point then its painless to add it as a hot spare. Plus I
don't think saving a few minutes is worth the extra hassle since
if a drive does fail he is probably going to be right there.
That array will have a rebuild time of 7 hours or so. Not a
big time savings. </div>
<div><br>
</div>
<div>
<div>
<div class="gmail_quote">On Sun, Oct 2, 2011 at 8:14 PM, Adam
Tauno Williams <span dir="ltr"><<a
moz-do-not-send="true"
href="mailto:awilliam@whitemice.org">awilliam@whitemice.org</a>></span>
wrote:<br>
<blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt
0.8ex; border-left: 1px solid rgb(204, 204, 204);
padding-left: 1ex;">
<div class="im">On Fri, 2011-09-30 at 18:55 -0400, Richard
Nienhuis wrote:<br>
> Performance issues are going to be inconsequential
for a machine<br>
> playing music. In degraded mode there is probably
still enough<br>
> performance. Also hot spare isn't going to spare
you from the time to<br>
> rebuild the array.<br>
<br>
</div>
???? I just can't express in words how strongly,
completely,<br>
absolutely, and utterly I disagree with the statement:
"Hot spare isn't<br>
<div class="im">going to spare you from the time to
rebuild the array."<br>
<br>
</div>
That is like saying ice is hot and water is dry.<br>
<br>
A hot spare means - Rebuilding the array actually
starts!!!!<br>
<br>
The sooner it starts the sooner it is complete and the
redundancy<br>
underlying the data is restored. A RAID solution without
a hot spare is<br>
a sports car with only three tires.<br>
<div>
<div class="h5"><br>
<br>
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