hardware

[Ed McNierney]

Rich -

That is true (about the RAID 5 generalization) but if you're looking for
MapServer (e.g. read) performance, it's a safe bet that it's a good
decision.  But it's also one that can be implemented badly (especially
if you're running PostgreSQL on the same machine).

In my experience with RAID 5 controllers I have found that the "poor
write performance" issue is true but usually exaggerated in the minds of
users (many controllers offer battery-backed RAM as a write cache, for
example), but that simultaneous read/write performance can be VERY bad.

The "make the array larger" question, while true, is part of a much more
complex discussion of expandability - the array enclosure might be out
of slots, for example, regardless of which RAID format you choose!

     - Ed

-----Original Message-----
From: UMN MapServer Users List [mailto:MAPSERVER-USERS at LISTS.UMN.EDU] On
Behalf Of rich.fromm
Sent: Tuesday, January 08, 2008 1:17 PM
To: MAPSERVER-USERS at LISTS.UMN.EDU
Subject: Re: [UMN_MAPSERVER-USERS] hardware

Ed McNierney wrote:
> 
> Third, I do agree that fast RAID 5 disks and lots of RAM are always a
good
> idea!
> 

Yes, for working with large data sets, more memory is in most cases
likely
to be more important than a faster CPU.

But to speak out against sweeping generalizations, I wouldn't
necessarily
agree that RAID 5 is always a good idea.  There are pros and cons, and
it
depends on your circumstances.  If I remember right (and it's been a
while
since I studied the details), the biggest downside of RAID 5 is that
small
writes are slower, because of the need to write both the data disk and
the
parity disk.  With most RAID controllers I believe (there might be
exceptions) there are also limitations concerning incremental
upgradability
of the array.  (e.g. what happens if I have N disks and I just want to
add 1
or 2 more)

- Rich

-- 
View this message in context:
http://www.nabble.com/hardware-tp14682251p14695423.html
Sent from the Mapserver - User mailing list archive at Nabble.com.