[Techtalk] Software vs. Hardware RAID

Andrew showork at adelphia.net
Tue Aug 20 02:28:24 EST 2002


	It sounds a bit like I may have inadvertently stepped on your 
toes. Honest, I am at a loss.
	Just getting the thing working is the goal. At least for me.
	How does one get 7 IDE drives...1 CD, 1 CDRW, 4 HD drives, 
(and Now) 1-15gb, to work with only two Motherboard slots. I chose 
the only thing I knew, go with a PCI card w/two additional 
slots(channels). It seems it can be configured either way. I got that 
far, no further, but have done it as a combination and as singles. It 
just stops there.
	Would setting the jumpers on the 4 drives to slave and master 
instead of cable select, go toward solving my problem? Would that 
allow the boot process to continue?


>I am the person who expressed a preference for software RAID. Since this
>issue has been debated at great length elsewhere, I'd prefer to not do so
>here. But for the information of those who wish to make their own
>decision, here are some links and quotes:
>First, from Linuxplanet's nice tutorial:
>>  Software RAID can be organized with the help of the OS and it doesn't
>>  need anything except additional CPU time for its support. But, CPU time
>>  is the cheapest resource among all that we have. There is myth that states
>>  hardware RAID is always better than software RAID. Hardware sellers like
>>  this myth very much, for reasons which you can well understand. We can
>>  also hear the same line of thinking from system administrators, too,
>>  though nobody knows why.
>The rest of the remarks can be reviewed at:
>	http://www.linuxplanet.com/linuxplanet/tutorials/4349/2/
>However, from the NT era (1999 or earlier), we have this point of view:
>>  Hardware vs. Software RAID
>>  Just like any other application, software-based arrays occupy host
>>  system memory, consume CPU cycles and are operating system dependent. By
>>  contending with other applications that are running concurrently for
>>  host CPU cycles and memory, software-based arrays degrade overall server
>>  performance. Also, unlike hardware-based arrays, the performance of a
>>  software-based array is directly dependent on server CPU performance and
>>  load.
>The rest of this work can be viewed at:
>	http://www.uni-mainz.de/~neuffer/scsi/what_is_raid.html
>Fishing around you'll find quite a few debates -- and some benchmarks --
>to support both views, but the software crowd seems to be gaining ground
>lately. I do not think the popularity of an idea is a good metric, though.
>	The flexibility of the linux software approach is very appealing
>to some. The OS-independence of hardware is appealing to others.
>	This is presented not to try to convince anyone, but to let
>everyone know there are rational people who think, even if one has a
>hardware subsystem, there may be reasons to consider using software RAID
>instead. This idea was first presented to me by someone doing just that,
>having tested both systems.
>	More to the point, if you have a hardware setup and would like to
>compare its capabilities and idiosyncracies with software on linux, review
>the excellent faq at:
>	http://www.tldp.org/FAQ/Linux-RAID-FAQ/
>My own experience setting it up with quad Reiser partitions took, if I
>recall correctly, a couple of hours (mostly being nervous). But it was
>very easy, and works fine. The partitions do not have to match (but should
>be close if possible) and the disks do not have to match (but the slowest
>will be the limiting factor in some setups).
>I _do not_ think there is one _always right_ solution. I have, however,
>become familiar with reports of several people having trouble with
>hardware setups that disappeared when they switched to the linux
>implementation. I would actually be interested to hear if anyone has seen
>the reverse effect, as I have not heard of any such.
>	However, that should not be surprising when one considers that the
>software implementation costs less, and is easy to experiment with, so I
>suspect quite a lot of new linux RAID users head straight for the software
>setup without trying hardware at all (that would be, for example, me).
>	And if hardware starts goofing up on you, the cheapest fix is, of
>course, to just move to software. The converse is not true.
>Techtalk mailing list
>Techtalk at linuxchix.org


	    Have a nice Day!,

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