On Jun 14, 2005, at 8:48 AM, Wojciech Puchar wrote:
think twice before making RAID-5 array. are you sure small writes
will not be too common?
No, you are on to something - I will be making small writes / parity
calculations. This is going to be a web server but it is for clients
and they do have sites running with SQL backends and not just static
HTML content.
i think buying 4 80GB FAST IDE/SATA drives and arranging it as
RAID-10 will give you 160GB of FAST and protected storage.
performance gain using mirror+strip will likely offset this of
using faster 15k rpm drives.
and it will be for sure cheaper. you may put 6 drives (RAID-10) and
even larger drives and still have cheaper alternative and even
faster. and MUCH more space.
Sure, it will be cheaper. For me it's too late, I've purchased the 4
x SCSI 15k drives I need for this project. I have bought mostly
unopened, in-box but secondhand IBM drives/sleds. They are still
expensive but certainly not the (what I consider) insane prices for
the same drives IBM direct. I'm paying around 1/3 of "list".
I'm curious as to if you're right, I'll certainly have something to
run some benchmarks on soon. Keep in mind this is all running though
hardware raid (IBM ServeRAID 6i). Somehow I feel that 15k SCSI on
U320 being processed as RAID-5 with this card will be better than you
state. You're right, it will have cost more than IDE but I wanted to
give this approach a try.
Worst thing is that I can fall back to SCSI 1+0 as you suggest at the
cost of one drive's space. My guess is that while the drives are
clean I will play with both structures for the RAID and compare some
benchmarks to give me an idea of what kind of hit the parity is
costing me.
Thanks for you comments.
d.
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