* Robert Woodcock <[email protected]> wrote on [01-03-10y 19:20]: > On Sun, Jan 03, 2010 at 03:11:25PM -0800, Ryan Allen wrote: > > Hi SSL, > > > > I just purchased 4 new 1TB SATA drives, and attempted to upgrade my > > RAID 5 system to 3 TB. however my Dell CERC 6 channel SATA RAID card > > will only let me build a RAID volume up to 2 TB. > > > > I couldn't find any firmware upgrades on this horribly supported > > el-cheepo raid card. At least its been a solid work horse, with > > little problems aside from a horrible UI utility called afacli. > > > > I am looking for a hardware RAID card, PCI-X (100MHz), that has an > > fairly easy to use UI that is well supported in Linux. It should > > also take advantage of ALL my drive space for an expected volume of a > > little under 3TB. > > > > Any suggestions? I would like to not spend $550 on an fancy 3ware > > card either. Anything in the $100 range? > > You may not have much money to spend on this, but surely this data is > important to you? > > With a multi-terabyte array, the chance of silent data corruption leading to > later rebuild failure exceeds 50% with RAID4/5.
I am quite interested in this statistic. Where does this 50% come from? We have all seen the math. If one drive has a 5% chance of failure in one year, the chances of two drives failing --at the same time-- is multiplicitive (.05^2), or .25%. Of course having more then two disks increases the chances that multiple drive could fail at the same time. I'm under the firm belief that anybody can have a solid, secure, and more affordable RAID 5 setup if 1) you have a decently small number of disks, say <= 6, and 2) the user replaces any failed disks (SMART, or other failure indicators) as quickly as they can, and 3) have a solid backup plan in place. This will cut hardware budget by around 40%, and consume less power. > And yes, I have had enough > personal experience for it to be statistically valid. I have not had much > better luck with RAID6 either. No more: http://baarf.com/ > > You'll have much better luck with RAID1 or RAID10. You could do it with the > equipment you have if you're willing to live with 2TB of space. > Yes, of course RAID1 is more "secure". Just as a monorail from Ballard to West Seattle will provide traffic free mass transit, Seattle never built one. Why? Money and management. Every engineering decision has a trade off. In this case the requirements are to conserve money and electricity. > You're almost guaranteed to get "fake RAID" in a $100 4-port controller. > You're certainly not going to get a battery backup unit for that, which is > *essential* for decent performance with RAID5. Can you enlighten me on the importance of "battery backed RAID cards" when the entire system is on a massive UPS, programmed to do a clean shutdown on power failure? The system in mind has been tuned to do a worst case shutdown in just under 1/3 the measured battery life. > Oh, and you'll probably want to double check that it really is a RAID card > limitation and not just a partitioning problem - the classic MBR partition > format only supports 2TB drives. You have to use something more sane (such > as GPT) to partition a larger drive. Yeah, its the configuration utility at the system BIOS startup. Before the OS boots, its the hardware is preventing me from creating the RAID set. > -- > Robert Woodcock - [email protected] > "Down, not Across" > -- alt.sysadmin.recovery -- +-----------------------------+ | [email protected] | | http://www.the-summit.net | +-----------------------------+
