“Gotten away with” I’m sure meant “hasn’t been bit by” not “has evaded authorities” in this context I’m sure.

 

Monitoring systems is great and certainly can help prevent the situation many find themselves in where they aren’t monitoring and lose a disk without realizing it then lose another later and go crashing to the floor.

 

However,   many of us have run into the scenario where we ARE monitoring and know exactly when the first drive failed and/or have a hot spare that automatically starts rebuilding the moment it does fail but despite being that proactive have had another drive fail while the rebuild was in progress and thereby lost the entire RAID5 set.   RAID5 is certainly better than JBOD because it does provide some redundancy but in very large arrays it makes sense to try to use a better RAID level OR to split it into multiple RAID5 sets to minimize how much is lost when this happens.  The more disks you have in a single RAID5 set the more likely it is you’re going to experience such a double disk failure at some point.

 

 

First of all, suck it Neil Conner.  I’m about to disagree with Ed (again) and there is nothing you and your fish eating friends can do about it.

 

Gotten away with it? I’m not stealing bread from the supermarket, I’ve made a calculated decision. I run 18 MD1000s in this configuration globally and I have yet to lose an array. The added capacity and speed benefit of a 15 disk raid array (no hot spare) is plenty worth the risk of the array going down.  Further, this risk is mitigated with properly configured Dell OpenManage which alerts me immediately if a disk fails so I can have it replaced.

 

Sure, I may eventually lose an array, but this is backup data. It’s importance to most businesses is somewhere between Dev and QA, and if I were (worst case scenario) to lose a Raid5 and 10TB of backup data, then I’d inform the appropriate application groups and move on. It’s not like most of the data isn’t probably ok (backup not needed) or on tape (array not needed) or has incremental available (also on tape.) This isn’t a production database or file server, it’s backups, IMO, Ed’s “every bit counts” attitude is completely out of step with the real world.

 

-Jonathan

 

PS: I do agree with Ed about 1TB disks, but in my case because of the poor performance not the raid implications. 15 x 500GB SATA in a Raid-5 is the backbone of my  operation.