The portable cache module is basically extra cache RAM for your controller, but has one very important feature: it's battery backed. That way if the server loses power while data is waiting to be written to disk, you won't lose data. This is especially important for databases. It is also important to enable write-back cache if you have battery backed cache. If you don't have battery backed cache then you really should do write-through to prevent data lose. The difference between write-back and write-through is write-back stores the data to be written in cache and tells the operating system it can continue. Write-through makes the OS wait, which is slower. Some controllers allow you to adjust what percentage of cache is used for reads and writes. If the controller has 256MB of cache, I'd just give 50% to each and see how things perform. It depends on how your database is being used, but if you have 256MB of cache and are read heavy, I'd consider testing 75% read, 25% write. One last recommendation, you may want to consider getting 6 or 8 drives and doing RAID 1+0. The performance is much better for reads and writes than a RAID 1 and a RAID 5, plus you're still redundant. Give this a read: http://aput.net/~jheiss/raid10. -Chris Robert De Mars wrote: > Hello, and a good day to you all. I am about to order a new server for my > job, and I was wondering about the raid controller option. > > The box is going to used for running a very busy database. > > I have the option for > Intel SAS RAID Controller or > Intel SAS RAID Controller w/ Portable Cache Module (Add $450.00) > > I am planning on running 2 drives as raid 1 for the OS (Slackware), and 3 > drives as raid 5 for the database. > > What is the benefit of the Portable cache module. I am not concerned about > the price, just if this is something I should consider. > > Any thought would be great. > > Thank You!!! > > Robert De Mars > http://b-o-b.homelinux.com > > _______________________________________________ > TCLUG Mailing List - Minneapolis/St. Paul, Minnesota > tclug-list at mn-linux.org > http://mailman.mn-linux.org/mailman/listinfo/tclug-list >