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<div class="moz-cite-prefix">Because the probability of having an
unrecoverable read error on RAID5 rebuild starts to come up off
the peg and RAID6 isn't much better. <br>
<br>
Since they came on the market, I've found that NASses both cheap
(e.g., LaCie) and expensive (IBM-rebadged NetApp where you paid
extra by the protocol) aren't worth spit. Sure, they work (sort
of - I got a LaCie guy to admit to me once that their NFS
implementation was badly broken but they didn't really care), but
the sorts of things you may expect to do administratively, like
make fast copies internally, scan for viruses, or search for files
(for instance, because someone had an errant mouse drag that moved
their quarterly report spreadsheets to God-knows-where) are
ruinously slow. To give you some idea, I once replaced said
rebadged NetApp - that cost about $40,000 - with a
SuperMicro-based Gentoo Linux file server with a mix of SAS and
SATA drives in 24 slots in the front, two SSDs inside, two SAS
controllers (with RAID10 with the RAID1 pairs split across
controllers so a controller would die and you still wouldn't lose
the volume), and two four-core CPUs. All that plus a warm-swap
machine, spare mobo, spare CPUs, power supplies, NICs, disk
controllers, and RAM (to heck with waiting for some schmoe from
e.g. IBM's field service contractor to find your site and replace
parts in a machine he might have never seen before anyway) cost
about $25K, and it could scan its main shared-space volume with
clamav at over 200MiB/s. In-slot NICs were bonded for I/O (the
on-mobo NICs were not used in order to reduce the risk to the
mobo). It was NFSv3-ready, had Samba of course, and daemons for
anonymous chrooted FTP and rsync - and there was talk at one time
of having it serve out CVS (it'd might as well!). <br>
<br>
So when you talk to me about what RAID configuration I'd recommend
for 12x2TB drives in a NAS, I'm thinking of the operational risks
you've baked into your IT resources just by having a NAS in the
first place and wondering whether or not RAID nuances would matter
all that much at the end of the day. Ask yourself this: even if
it were just half full, how long would it take you to do a
complete read for backup-making purposes? See, in this day and
age, it's real easy to have giant amounts of storage and therefore
giant amounts of stuff being stored, all connected to everything
else by what are very tiny pipes, relatively speaking. <br>
<br>
On 2/12/14, 6:43 PM, Ray Vastly wrote:<br>
</div>
<blockquote
cite="mid:CABYGJkmyvJ=8YtKOrW9Wh9txay-ieC-bTkQF8C2DGwFVQ4UCMw@mail.gmail.com"
type="cite">
<p dir="ltr">Why should you avoid raid 5 or 6 when using large
hard disks? What Raid configuration would you recommend for 12
HDDs each 2 TB in a NAS?</p>
<div class="gmail_quote">On Feb 12, 2014 6:40 PM, "Jeff Hubbs"
<<a moz-do-not-send="true" href="mailto:jhubbslist@att.net">jhubbslist@att.net</a>>
wrote:<br type="attribution">
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">
<div bgcolor="#FFFFFF" text="#000000">
<div>On 2/12/14, 5:00 PM, Lightner, Jeff wrote:<br>
</div>
<blockquote type="cite">
<div><snip><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"></span>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"> </span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">You
really should be using RAID6 or RAID10 rather than
RAID5 as it is even more redundant (i.e. can survive
2 disks failures). </span></p>
</div>
</blockquote>
And you shouldn't be using RAID5 or RAID6 at all if your
drives are 750-1000GB or larger. <br>
<br>
Mail and database servers would be two good places to make
use of snapshotting filesystems. Note that some email
systems that use message stores go insane if the message
store is not in the state that the rest of the email system
presumes it's in, so you have to make sure that your
backup/recovery scheme doesn't capture messages and message
metadata/index in different states.<br>
<br>
<br>
</div>
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