RAID "50" is normally implemented by using RAID 5 in hardware, and using software to stripe across the RAID 5 protected devices.
There is also RAID 6, which is similar to RAID 5 except that there is dual parity, allowing two drives to fail in an array without data loss. The STK "Iceberg" architecture(IBM RVA/STK SVA) implements RAID 6. I'm not aware of RAID 6 being implemented in software, but someone somewhere has probably done it. I guess if you group devices into a RAID 0 array on an SVA, you are using RAID 60. Maybe I'll set up a software RAID 5 over our RAID 6 hardware and create the world's first RAID 65. While generally more expensive, RAID in hardware often pushes most of the RAID management issues out of the user's way, allowing them to just use the devices. For example, drive failure recovery is often automated to the point that a hot spare is dynamically added into the array of the failing drive, the failing drive is put offline, and a service call is automatically placed. There is a good new (as in 2003) O'Reilly book authored by Derek Vadala called "Managing RAID on Linux". It covers all of the md driver stuff, which is what is normally used for software RAID on Linux. It also has a chapter on filesystems and one on HBAs. http://press.oreilly.com/mraidlinux.html Scott Ledbetter StorageTek -----Original Message----- From: Mark D Pace [mailto:[EMAIL PROTECTED]] Sent: February 10, 2003 1:48 PM To: [EMAIL PROTECTED] Subject: Re: raid question >I don't know if it applies to Linux, but I vaguely remember a RAID 1+0 where >the data is both striped and mirrored. Is this superior to RAID 5? Also, for >the very paranoid, I would guess that one could use a RAID 5+0 where the >data is striped w/parity like RAID 5, then each RAID 5 volume is mirrored. >This would seem very excessive, but very safe. RAID0+1 is exactly as you described, a striped RAID0 array plus a mirror of each drive. The downside to mirror is that you are "wasting" 1/2 of the available DASD space. It's there only if you have a problem. With RAID5 you don't "waste" space. All the DASD space is useable (okay so not all, but almost all). So it's a juggling act between cost for hardware and protection. I don't know if there is such a thing as RAID5+1. Mark D Pace Senior Systems Engineer Mainline Information Systems 1700 Summit Lake Drive Tallahassee, FL. 32317 [EMAIL PROTECTED] Office: 850.219.5184 Fax: 850.219.5050 http://www.mainline.com
