Matt Wisdom wrote: > > 10 drive raid Which controller? Chipset? Battery backup? RAM?
> What RAID config would you use for the databases? Depends on what RAID controller you have. If it is IOP321 based, 10 disks in a RAID 6 or 9 disks in a RAID 5 and a hotspare. > How important is (battery backed) write cache for the raid? It is the single most important way to improve performance on the hardware side. With a RAID system, every write command requires at least 2 physical writes: every bit has to be stored on at least 2 disks. Even if the write heads are perfectly positioned for the write operation, a disk rotating at 10000 rpm will take on average 3 ms for the write. With 2 disks, that becomes 4.3 ms, and with a RAID configuration that requires you to write more disks that approaches asymptotically to 6 ms. And that is the theoretical optimum with perfectly positioned heads. Since the ACID Durability requirement mandates that all changes are logged to physical storage, you can not commit more then 160 transactions that require writes per second on such a system. It is physically impossible. A battery backed cache allows you to overcome this limitation because it allows the controller to group writes together in batches, without the database having to wait. Jochem ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~| Now there’s a better way to fax. eFax makes it possible to use your existing email account to send and receive faxes. Try eFax free. http://www.houseoffusion.com/banners/view.cfm?bannerid=63 Message: http://www.houseoffusion.com/lists.cfm/link=i:4:190621 Archives: http://www.houseoffusion.com/cf_lists/threads.cfm/4 Subscription: http://www.houseoffusion.com/lists.cfm/link=s:4 Unsubscribe: http://www.houseoffusion.com/cf_lists/unsubscribe.cfm?user=89.70.4 Donations & Support: http://www.houseoffusion.com/tiny.cfm/54
