Even in degraded mode or re-building, my array is faster much faster than my network. I have 100BaseTX Full duplex, so I can read and write a total of 20Meg per second. My array is faster than that! If your RAID5 arrays were software, the md driver will slow the re-build when other disk access is needed. These 2 files help control the speed: /proc/sys/dev/raid/speed_limit_max /proc/sys/dev/raid/speed_limit_min Since your RAID5 arrays are hardware, you may have a re-build priority that can be adjusted. In your case you would want low priority. I prefer to be safe, I always give the array re-build the highest priority. I would go with the hot spare. Once the first disk fails, you are at risk of losing everything if a second disk fails. Even during the re-build, if a second disk fails, game over man, game over! But once the re-build is finished, you are safe again. Safe for another single disk failure that is. But, if you have a daily backup, and you are willing to risk losing 1 days work, that is your choice! >From what I have read, RAID0 will just go as fast as your slowest disk. Your RAID5 re-building will not hurt the RAID0 array. It will just slow it down. Guy Sure you saved money, but at what cost? - "Guy Watkins" -----Original Message----- From: linux-raid-owner@xxxxxxxxxxxxxxx [mailto:linux-raid-owner@xxxxxxxxxxxxxxx] On Behalf Of AndyLiebman@xxxxxxx Sent: Monday, September 20, 2004 9:51 AM To: jlb17@xxxxxxxx Cc: linux-raid@xxxxxxxxxxxxxxx Subject: Re: Software RAID-0 striping over Hardware RAID-5 jlb17@xxxxxxxx writes: > I have a couple of dual 3ware boxes I do this with, and have never had a > problem. I would make sure that you have a hot spare on your RAID5 > arrays, though. Because if one of them dies, you'll obviously lose > everything on both arrays. Thanks for the reply, Joshua. Have you ever tested your systems while one of your RAID5 arrays is rebuilding or verifying? (I'm about to do that right now). I'm wondering if Linux Software RAID-0 might falter if one of the two arrays is significantly slower than the other (while rebuilding)? To test the integrity of the system, I'm going to remove a drive from one of the RAID5 arrays, add it back and rebuild the array, and while the rebuilding is taking place I'm going to run Bonnie++ several times (100GB of writing/reading per test). My inclination is to not use a hot spare. Instead, I rely on 3ware's email notification feature to alert me that a drive needs to be replaced. I always keep a spare handy that can be popped into place immediately. Also, I want to have control over when rebuilding takes place. It would be a bad thing to rebuild during certain critical high I/O moments of the day -- whereas rebuilding at night would be much less stressful on the system. Do you see anything wrong with this approach? Thanks again, Andy - To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html - To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
