[This is a second re-send to see if we've fixed the weird line-break = problem I've been having with this list for the past few weeks.] The "4W" part of the RAID 5 formula is actually true only for RAID 5 = groups larger than 4 disks. On a 3-disk RAID 5 array, for example, both large writes and small writes will consume only 3W I/O calls (one for each = disk). The complete formula is actually R + min(4,G)*W. Since most of you have = G>3, the simplified formula that uses '4' as a constant yields the correct answer. In the spirit of my prior note, if you use RAID 1, the formula is still = R + min(4,G)*W (yes, the same one, because RAID 1+0 is actually the same = thing as RAID 5 with G=3D2). Because for RAID 1+0, the value of G is G=3D2, = the formula simplifies to R + 2W. My original post neglected to mention the = '2' in this formula. My apologies. Note, however, that R + 4W > R + 2W for all values W > 0, which was the point that I had intended to convey originally. Cary Millsap Hotsos Enterprises, Ltd. http://www.hotsos.com * Nullius in verba * Upcoming events: - Performance Diagnosis 101: 9/14 San Francisco, 10/5 Charlotte, 10/26 Toronto - SQL Optimization 101: 9/20 Hartford, 10/18 New Orleans - Hotsos Symposium 2005: March 6-10 Dallas - Visit www.hotsos.com for schedule details... -- To unsubscribe - mailto:oracle-l-request@xxxxxxxxxxxxx&subject=unsubscribe To search the archives - //www.freelists.org/archives/oracle-l/