On Jun 16, 2011, at 20:43, Greg Smith wrote:
> The layout you proposed (OS+WAL , data) might be effective, but if your write volume is low it may not be much of an
improvementat all over a simple RAID1 of two drives. The odds that you are going to correctly lay out individual
sectionsof a disk array with only two pairs to spread the data across aren't good. If this is all you have to work
with,a 4-disk RAID10 would at least guarantee you're taking advantage of all four drives. With that controller, it
shouldbe almost twice as fast in all cases as hooking up only two drives.
The data is more or less constantly rewritten (it contains hourly updated travel related data). Therefore, I really
tendto buy 4 disks from the start on.
> There is another possibility I would suggest you consider. You could buy the server with a single pair of drives
now,then wait to see what performance is like before filling the other two slots. It is far easier to figure out what
drivetechnology makes sense if you have measurements from an existing system to guide that decision. And you may be
ableto get newer drives from your vendor that slide into the empty slots. You may not ever even need more than a
singleRAID-1 pair. I see lots of people waste money on drives that would be better spent on RAM.
Actually, there are already two older servers in place right now. The data is about 14GB in size and slowly rising.
Consideringthe price for RAM I can easily afford to install more RAM than the db data is in size. I was aiming for
24GB.But even then, I cannot be sure that no queries will read from the disk. AFAIK, there is no way to force all the
datato stay in cache (shared_buffers for example).
Thank you for your input so far.
Regards,
Tom.
