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RAID Controller Batteries Time Bombs Waiting to Blow
We spotted a LSI RAID controller battery pack in one of our lab servers that became severely deformed over the years. That highlights the importance of maintaining RAID controller batteries
hardware  storage  energy  raid 
16 days ago by pankkake
[2010] Why RAID 6 stops working in 2019 | ZDNet
"Three years ago I warned that RAID 5 would stop working in 2009. Sure enough, no enterprise storage vendor now recommends RAID 5. Now it's RAID 6, which protects against 2 drive failures. But in 2019 even RAID 6 won't protect your data. Here's why."
storage  disk  raid 
16 days ago by ddribin
[2009] Triple-Parity RAID and Beyond - ACM Queue
"How much longer will current RAID techniques persevere? The RAID levels were codified in the late 1980s; double-parity RAID, known as RAID-6, is the current standard for high-availability, space-efficient storage. The incredible growth of hard-drive capacities, however, could impose serious limitations on the reliability even of RAID-6 systems. Recent trends in hard drives show that triple-parity RAID must soon become pervasive."
storage  disk  raid 
16 days ago by ddribin
Converting RAID5 to RAID6 in mdadm
RAID5 arrays are useful for pooling storage devices together and providing fault tolerance in the event of a drive or data failure. A storage array configured for RAID5 can tolerate the loss of 1 disk or volume without losing any data. Using maths, a RAID5 array that has experienced a failure from one volume can be rebuilt using the remaining volumes. Super awesome for when a drive fails, you will not lose your data!

Until now... hard drives have massive storage capacities, 4TB drives are available to consumers as of May 2013. If a RAID5 array is comprised of large capacity disks, it will take longer to rebuild the array in the event of a failed volume. During the rebuild process the entire array is at risk and can not support the loss of another volume. As the rebuild process is very intensive on the volumes that it is made up of, the risk of failure of another disk is generally higher during the rebuild process. Enter RAID6.

RAID6 is the new industry standard for storage arrays that are comprised of high capacity disks. An array that is built as RAID6 can support the failure of 2 devices without data loss. That fault tolerance level increases the probability of a successful rebuild in the event of a lost volume.

The increased fault tolerance of RAID6 is made possible by the use of two parity blocks per stripe, where as RAID5 only has one parity block per stripe. This means that while a RAID5 array's storage space can be calculated by ((number of disks - 1) * disk size), RAID6 is calculated by ((number of disks -2) * disk size). Reworded: with RAID6 you lose two disks' worth of capacity while with RAID5 you only lose one disk's capacity.

The decision to move from RAID5 to RAID6 is convincing once you have a high capacity RAID5 array that experiences a volume failure and you are sweating the array rebuild for 4 or more days. Which is what happened in my case so I decided to move to RAID6 for extra protection. Here is how to convert a RAID5 array to RAID6 using mdadm. Keep in mind that because RAID6 would have less total capacity than a RAID5 array with the same number of volumes, a new disk must be added to the array before it can be converted if you wish to preserve the data.

The steps outlined below can cause data loss. Do not run them on a production system without fully understanding the process and testing in a development environment.

These instructions are not meant to be exhaustive and may not be appropriate for your environment. Always check with your hardware and software vendors for the appropriate steps to manage your infrastructure.
raid  ubuntu  sysadmin  linux 
23 days ago by mlednor
How To Manage RAID Arrays with mdadm on Ubuntu 16.04 | DigitalOcean
RAID arrays provide increased performance and redundancy by combining individual disks into virtual storage devices in specific configurations. In Linux, the mdadm utility makes it easy to create and manage software RAID arrays.

In a previous guide, we covered how to create RAID arrays with mdadm on Ubuntu 16.04. In this guide, we will demonstrate how to manage RAID arrays on an Ubuntu 16.04 server. Managing RAID arrays is quite straight forward in most cases.
ubuntu  raid 
23 days ago by mlednor
BTRFS convert RAID1 to JBOD with btrfs.
btrfs balance start -dconvert=single /mnt

btrfs  raid  convert_to_single 
24 days ago by quasiperfect

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