RE: General RAID5 question - dangers?

Thank you for the clarifications. I agree that due to the fact you are doing a lot more reads for a write you are somewhat more susceptible to errors. But the percentage of writes to reads on most systems I have seen is low. So the number of reads you are adding wouldn't seem that high. I agree the grumbles about RAID 5 are loud enough to make one think. Any reason for not pushing RAID 3 as a feasible option over RAID 5? I guess maybe availability of hardware to do RAID 3 might be a factor. I am not against pushing RAID 10 by any stretch of the imagination, but as far as parity going out of whack, RAID 3 would seem an ideal solution for preventing that from occuring. As far as cleaning your house, you pay transportation costs, I will send you an address to mail tickets and car rental to. Do you have hardwood floors, tile or carpet? (I would hate to bring the wrong cleaning supplies). Will P.S. I suggest RAID 10 whenever given the oppurtunity, but like I said before it is because I am a lazy bum who is scared of multiple disk failures. >===== Original Message From "Obnoxio The Clown" <obnoxio@hotmail.com> ===== >From: William Rice <ricew@operamail.com> >> >>I will admit to having some fear of RAID 5 but for different reasons. I >>like >>being >>able to lose 3 or 4 disks and still have at least a chance of not having to >>restore my data. This is mainly because I am a lazy bum who does > >That is a major plus of RAID10. > >>not like the idea of doing work which I do not have to. I am interested >>in the theory that due to the fact that parity is calculated it is more >>susceptible >>to error. Would you mind adding a little more meat to that argument, or >>is it based on more complex=more problems? Or maybe he fact that it >>reads all the other disks to get the information to change the parity so >>there is more oppurtunity for a problem? > >Well, any calculation or process is an opportunity to introduce errors. I'm >sure the vendors cope with the resilience issues in a number of different >ways, with greater or lesser success. > >However, another issue is that RAID3/4/5 require greater load on the disk >devices. If I read from a RAID10, I only hit the disks I need. If I read >from RAID5, every disk in the stripe gets hit for every read. This increases >the work on the disk, which in itself leads to quicker failure. > >But to me, it's all academic. Saving money on disk is silly, and if people >like Art (and my most recent .com customer) migrate away from RAID3/4/5 to >RAID10 (and Art manages more than 7TB of disk!!) because of the pain it >causes, and despite the cost "savings" that's a good enough endorsement for >me. I've seen a RAID5 let go, completely without warning. We knew the disks >were blown before the RAID did. We were just exceptionally lucky that we >didn't lose absolutely everything. > >This is not to say that RAID10 can't fail, *anything* can fail, but the >margin for failure is so much lower with RAID10 than RAID5 that I feel much >happier with the risk. > >>I have never been priveleged enough to witness a site using RAID 5 have >>serious issues, and am trying to understand where mirroring would help >>in such a situation > >Well, if that's your idea of a privilege, can I interest you in the >privilege of cleaning my house out every week for free? :-) >________________________________________________________________________ >Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com ------------------------------------------------------------ This e-mail has been sent to you courtesy of OperaMail, as a free service from Opera Software, makers of the award-winning Web Browser, Opera. Visit us at http://www.opera.com/ or our portal at: http://www.myopera.com/ Your free e-mail account is waiting at: http://www.operamail.com/ ------------------------------------------------------------