If I have 7 1TB disks, I will have 6TB usable. With RAID 5 we will take the sum total of the equally sized disks combined and reduce that number the the amount of just 1 of the disks to determine the capacity.įor example, If I have 3 1TB drives, I take the total capacity (3TB) and reduce it by the amount of one of them (1TB) for a total of 2 TB. The goal of RAID 5 is to seek a balance between capacity and redundancy. But they are generally less useful so they typically are not included in discussion and they won't be included here except to say that some of them can be used as transition points from RAID 1 to RAID 5 in a migration. Because of this, it can also be mirrored across multiple disks to give the ultimate protection against data loss decreasing your statistical chance of complete failure geometrically! Because of its simplicity, it is often used boot partitions. RAID 1 is ideal for anything that you really, really care about. After all, you only need one or the other for the whole thing to work. But it is simple to implement and easy to fix. Also, it is only as fast as a single drive. RAID 1 is twice as expensive as RAID 0 per megabyte of data. So we get lots of redundancy but at a cost. An instant backup of the data as it exists at present period of time. And if that drive is lost, we simply replace it and rebuild the array. With RAID one, we can lose either drive and be fine. Anytime there is a write operation, we write to both.
With RAID 1 we take just two disks to get the volume, capacity and speed of just one disk (you can use more than two disks but you will still only get the performance and capacity of the one) and we mirror them. RAID 1 is quite the opposite of RAID 0 in many regards.
It is probably the worst RAID to choose if you actually care about what is being written to the disk for any period of time. RAID 0 is sometimes used for fast caches, or for storing volatile data that is only needed for a short period of time. So where does RAID 0 make sense? Anywhere you have a need for speed and/or and the ability to shrug off a failure. Rather, there are options and reasons for choosing that option. There isn't a proper RAID combination here for every problem. Ok, it seems sort of useless then to use RAID 0 right? Yes and no. The more drives we add, the big and faster it becomes…and the more frequently it fails! This makes the life expectancy of our volume 6 months! Additionally, if we replace the drive and start over again, we'll lose the entire volume again, statistically, in another 6 months. With RAID 0, however, we will lose the entire volume if any one of them fail. That means, statistically, all of these drives will fail after a 5 year average. Imagine that each of these drives has a expected life of 5 years. Surely there must be a downside to this performance…and there is.
We would find that we now have a single 10 TB volume that is able to write to all 10 disks at the same time giving us about 10 times the performance. Let's imagine that we have 10 1TB hard drives and we make one big RAID 0. It can be both bigger and faster than any other RAID, however it has 0 redundancy and is statistically more likely to fail than just a single disk on its OWN! It can be done with as little as 2 disks ONLY and gets 100% of the volume of both of those disks and the performance is nearly double of those disks had they run alone. With RAID 0 we create a single volume from all the members and the data is stored across all disks. Which for ext4 will work just fine even on a live FS.Of all the RAID combinations, RAID 0 is the fastest and is very cheap. Once rebooted, resize the filesystem so it spreads to the extent of the enlarged partition: The partition table will have been modified but the kernel will not be able to take that into account as some partitions are mounted. Try to align things on a megabyte boundary that is for end, make it a multiple of 2048 minus 1. With same number (1), start and type but with a bigger end (taking care not to overlap with other partitions). P to print the partition table, take note of the number, start, end, type of vda1.