Re: [LAU] drive bays and hardware RAID

Below are some numbers on performance that correspond to the more normal
"musician" usage of RAID, which would be raid-1 to protect against data-loss
due to disk failure. Other levels of RAID end up being pretty unworkable,
esp in a situation where you're using removable Raid-pairs in media-bays to
store your media. And what's the point of doing Raid-5 (and wasting all that
disk space and hardware controllers) in a situation where the disk isn't
permanently mounted and needing to be online 24/7 -- aka a "server".

So it's important to characterize what you're trying to do before jumping to
wild conclusions about what is "stupid." Stupid for a server room might be
smart for a home recording setup. And far too often, i've watched supposedly
professional sysadmins screw up their fancy RAID setups and lose everybody's
data (they also forgot to check that the backups were actually valid) --
something that probably woulnd't have happened nearly as often if they'd
have just gotten a single SATA disk and hooked it up without RAID, perhaps
even on a standard "consumer" computer instead of their special overpriced
"server" equipment (don't even start me on when
<large-comp-co-killed-by-linux-and-now-acquired> would force their open
source projects to use their crap "server" equipment that performed worse
and were less reliable than some snot-nose gamer kid's rig.)

Anyways, enough talk, some numbers:

https://raid.wiki.kernel.org/index.php/Performance#Performance_of_raids_with_2_disks

> RAID type sequential read random read sequential write random write

Ordinary disk 82 34 67 56

RAID0 155 80 97 80

RAID1 80 35 72 55

RAID10,n2 79 56 69 48

RAID10,f2 150 79 70 55

You'll note that RAID-1 performs about the same as an ordinary disk. In some
cases of reading, RAID-1 can perform better than ordinary disks.

The other question to ponder, in this day and age of fast processors.....
how much are you actually getting out of your expenditure for a hardware
RAID controller. For example, the Areca 1280 was mentioned earlier (
http://www.google.com/products/catalog?q=Areca+1280&um=1&ie=UTF-8&cid=17994260225728143364&ei=y5rhS7avOJfONMfp2ZkD
)
-- $1,169 new!! For that price you could buy a whole other computer and let
its general purpose CPU's and LSW do all the RAID computations -- aka a disk
server. For that matter, why not just get a new 6-core processor (
http://www.anandtech.com/show/3674/amds-sixcore-phenom-ii-x6-1090t-1055t-reviewed
) instead
of a 4-core (or a 3 or 4 core instead of a 2 core) and when the additional
cores are done doing your RAID computations, you'll be able to use them for
more important and tangible things -- audio and graphics.

Isn't that a better use of potentially limited cash and space resources?

Niels
http://nielsmayer.com

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Received on Wed May 5 20:15:02 2010