1. hw vs sw RAID-0
I would like to know whether hardware or software RAID is better for my
particular application. I have two Seagate Cheetah 2.2 Gb SCSI disks in
a RAID-0 array controlled by a DPT PM2044UW controller to which is
attached a DPT RC4040 memory adapter with 8 Mb of RAM. This array is
used as the scratch space (as 1 large 4.4 Gb partition) for molecular
modeling calculations. The OS and molecular modeling software are run
from a separate IDE hard drive. The scratch files include one large
binary file which is usually 200 Mb in size but sometimes larger than 2
Gb. During one particularly long calculation I noticed that the RAID
array was being accessed every 8 seconds. In general, the I/O to the
array is regular, not random, although the frequency of access can vary
depending on the size of the calculation. For a particular
calculation, I think the size of each I/O transfer is probably
constant, but the size should differ quite a bit from calculation to
calculation (the I/O data consists of the values to many integrals; the
larger the molecule, the more integrals and the larger the I/O sizes).
I am currently using hardware RAID via the DPT controller, with a stripe
size of 128K (the default). I am using RedHat Linux 5.2 and the 2.2.9
kernel configured for SMP with two PII-450 cpus.
I read in one of the RAID HOWTOs that software RAID can in fact be
faster than hardware RAID, but no details were given on how to tell. As
I am not an expert, I don't want to reconfigure my system for software
RAID and risk screwing something up dreadfully, or reconfiguring things
non-optimally and coming to the wrong conclusion. Does anyone have a
good idea as to whether my application would likely be significantly
faster using software RAID rather than hardware RAID?
Best wishes to all,
Sent via Deja.com http://www.deja.com/
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