diskvast.blogg.se

I was merely making an observation and suggestion.

Unfortunately with 4 kids, 2, dogs, a job that consumes me 12-14 hrs a day 6 days a week and a demanding wife I've barely time to strum a guitar let alone setup another fraternity. Let's be generous and give them 2 days to rebuild. If you are using 4TB disks then your rebuild time will be at least ten hours. Today we use at least 1TB disks and their sequential write rate has only gone up to around 115MBps, the same math is 1,000,000MB / 115MBps = approximately 8700 seconds which is nearly two and a half hours. This is an acceptable rebuild time and ten years ago when we used 72GB disks RAID was good. For a 72GB disk with an 80MBps write rate we get 72,000MB / 80MBps = 900 seconds, about 15 minutes. The time it takes to recover from the failed disk cannot be less than the size of the disk divided by its sequential write speed. All of these RAID levels will use a single disk to replace a failed disk and all will need to fill the one disk with data. The fundamental problem is that it takes too long to fill the large disks we are now using just to regain redundancy. In general, RAID rebuild time depends on two things: the quantity of data being calculated and the capacity of the array itself smaller RAID can be rebuilt in just a few hours, while more complex ones can take well over 24 hours.

Here's some googling references about rebuild times on RAID arrays.