On Wed, 24 Jan 2001 21:06:20 +0100, you wrote: >> > How can it increate a probility of a disk crash? Is it just because of >using >> > two disks? >> > Is so, it is a nonsense. >> >> No. Disks come with a MTBF. If you add disks, this MTBF remains >> (almost) constant. The MTBF of the entire raid will then decrase >> when the number of disks increase. > >I wrote this already, so just for completeness: >Higher data loss probability is caused by usage of two disks. It has nothing >to do with RAID. >If you use two disks without RAID0, you have the same data loss probability.
you may have the same data loss probability per disk, but the RAID system creates 1 logical disk out of many physical disks, therefor, the probablity has to be worked out accros the one logical disk, because the data is split up accross the many disks, and cannot be recovered (from RAID 0) if any one drive fails in effect the probability of 1 drive maybe 1in10years, but that one drive is only 1/n of the single logical drive, n being the number of drives in the RAID array. 10 Drives set as RAID 0 failure rate of each individual drive = 1in 10 years 1 drive = 1/10 of logical drive each 1/10th of the logical drive has a probabilty of failure of 1/10yr 10 drives * 1/10 fails = 10/10 = 1/1 failure per year its all probability/statistics, and you can even get the chance of disk failure within the next 10 seconds as high 50% --- either it does or it doesnt !! same as the dice: >As a second example, consider this. What's the probability of rolling a "6"on >a single dice? It's 1/6 , right? either you do roll a 6 or you dont :) one thing is fact, hard disks *do* fail, when is often not important, the fact that you can carry on when they fail maybe more important in some situations, i.e. business.. yes, home.. not usually >I don't have a bus. I can't afford it. me niether, but i bet it'd be pretty cool going to work in your own bus :) >Have you ever heard about backuping? I practise this for years, and it >helped me much! Oh yes, but that doesnt recover the data since the last backup, ie the current days work :) > >> In my work as a administrator I have experienced about 15 disk >> crashes - ~10 of which were cheap PC IDE drives. 3-4 SCSI and one >> FW disks. >> >> -Frode > >Oh, we don't use neither RAID nor UPS at work. I wonder why, but I can't >change it. >:-( oh well, your time will come >;o) -- Dean Liversidge [EMAIL PROTECTED]
