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41 votes
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Low-end hardware RAID vs Software RAID

A 10-20$ "hardware" RAID card is nothing more than a opaque, binary driver blob running a crap software-only RAID implementation. Stay well away from it. A 200$ RAID card offer proper hardware ...
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18 votes

How to re-add a drive when RAID is in degraded mode?

Adding Back a RAID 1 Member To add a RAID member back into the array, use: mdadm <RAID Device> -a <Device to add into the array> For example: $ mdadm /dev/md0 -a /dev/sdc1 mdadm: re-...
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  • 1,103
17 votes

Why is RAID 1+6 not a more common layout?

Generally I'd say RAID 1+0 will tend to be more widely used than 1+5 or 1+6 because RAID 1+0 is reliable enough and provides marginally better performance and more usable storage. I think most people ...
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16 votes

Why is RAID 1+6 not a more common layout?

The practical answer lies somewhere at the intersection of hardware RAID controller specifications, average disk sizes, drive form-factors and server design. Most hardware RAID controllers are ...
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  • 194k
16 votes

Should I 'run in' one disk of a new RAID 1 pair to decrease the chance of a similar failure time?

It's a waste of time. You won't be able to induce failure or stress the drives in a meaningful manner. You have RAID, and that's a good start. Just make sure you have monitoring in place to actually ...
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13 votes
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How to add hot spare to software RAID1?

If you really want to use 4 disks for a RAID1 array, I suggest you to go with a 4-way RAID1 array. In this manner, should a disk fail, you continue to have triple-protection (3-way array) without ...
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12 votes

Why is RAID 1+6 not a more common layout?

You have diminishing returns on reliability. RAID 6 is pretty unlikely to compound failure even on nasty SATA drives with a 1 in 10^14 UBER rate. On FC/SAS drives your UBER is 1 in 10^16 and you get ...
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  • 3,697
12 votes
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How to obtain read speeds of two disks using mdadm/btrfs raid1 or zfs mirror?

The question is a bit limited on information as to how the test where done so I am assuming that you where just using dd to write directly to a file. BTRFS: In BTRFS terms RAID1 means TWO COPIES ...
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12 votes

Different RAID settings for different folders on the same logical drive

Raid is working on partitions (block devices) "under" the filesyetem. Raid has no job with folders or files on filesystem.
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  • 1,230
11 votes

Low-end hardware RAID vs Software RAID

Go ZFS. Seriously. It's so much better compared to hardware RAID, and reason is simple: It uses variable size strips so parity RAID modes (Z1 & Z2, RAID5 & RAID6) equivalents are performing @ ...
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11 votes
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Faulty RAID1 disk now shows as foreign

DO NOT import the foreign configuration. A drive shown as "Foreign" is one that the RAID controller thinks is part of a RAID array, but does not recognize as being part of an existing array on that ...
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10 votes
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Can Docker Corrupt a Software RAID Setup?

LXC/Docker by design doesn't have anything to do with RAID (any RAID) at all. Docker/LXC containers are run on the same kernel as the host. As such I don't think there are any docker related problems.
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10 votes
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Can mdadm convert a RAID5 to a RAID1?

You'd be left with only half the capacity, so if the file system was more than half full already, it would be impossible. Even if there is sufficiently free space, the operation involves resizing the ...
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9 votes

How to auto-start Degraded Software RAID1 under Debian 8.0.0 on boot?

The initramfs executes /scripts/local-top/mdadm to handle raid. In that script is the statement if $MDADM --assemble --scan --run --auto=yes${extra_args:+ $extra_args}; then verbose && ...
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8 votes

What's the difference between "mirror" and "raid1" in LVM?

The practical difference is that the 'raid1' mirror segment type always stores its logs (in fact, metadata subvolumes) on-disk on the same PVs as the lv being mirrored. You no-longer need a third pv ...
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  • 461
8 votes
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mdadm 3-way RAID 1 - good solution for guaranteed 2-drive failure tolerance?

To have a single array capable of 2-disk failure, you have two choices: three-way RAID1, as you suggested RAID6, as another possibility. What is the best choice? It depends of what you are trying to ...
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8 votes

4-Drive Software RAID1 vs RAID10 for Extreme Reliability Purposes

In such a setup (4 disks and RAID1 only), it is better to directly use the 4th disk as an array member rather than as a spare. Using it as a spare will not buy you anything on the redundancy side, ...
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8 votes

Different RAID settings for different folders on the same logical drive

Perfectly feasible nowadays. You need to create two volumes, one RAID and one non-RAID. Mount the RAID volume as X:, mount the second other as X:\subfolder.
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  • 690
8 votes

Getting files out of XFS with 64kb block size

I've done a bit of research into your problem. Not easy but looks feasible. The area of code breaking you is this (well, in newer kernels): fs/xfs/libxfs/xfs_sb.c 271 /* 272 * ...
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  • 22.7k
7 votes

How to delete removed devices from a mdadm RAID1?

In your specific case: mdadm --grow /dev/md1 --raid-devices=3 For everyone else, set --raid-devices to however many functioning devices are in the array currently.
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  • 265
7 votes

HP Smart Array P410: Convert RAID10 to RAID1 OR remove disks from RAID10

I don't participate here as much as I used to, but I see a problem with what you've done. HP Smart Array controllers can accommodate SAS and SATA disks. However, you cannot have an array comprised of ...
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  • 194k
6 votes

mdadm 3-way RAID 1 - good solution for guaranteed 2-drive failure tolerance?

Yes, you can add as many mirrors to a RAID1 as you like, and you can tolerate failures of all but 1 device. If you add 10 devices, you can tolerate a failure of 9 devices. Don't forget there will be ...
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6 votes
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How RAID 1 and RAID 10 become different when there are 8 logical disk?

The 2nd example is not RAID 1, but nested RAID 0+1, mirror of stripes (as 10 is stripe of mirrors). While it is obvious what's the difference between RAID 0+1 and RAID 1+0 with an odd number of disks,...
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  • 42.5k
6 votes

How to Resize RAID partitions on Ubuntu Server 16.04

The recommended way to avoid the space problem in your situation is to move existing directories to the filesystem in /dev/md2, and use symlinks to point to the new directory. Resizing the MD device ...
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6 votes

Raid 1 backup or backup of backup

RAID - no matter what level - is not a backup. It is hardware redundancy and is meant to mitigate any loss of either data OR run time/uptime due to sudden catastrophic hardware failure. RAID will ...
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  • 1,438
6 votes
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2 x RAID1 vs. RAID10 with four disks

RAID 10 is just stripes over mirrors. That means for every mirror pair only one drive may fail. You also lose 50% of the storage. I don't know how your NAS handles two RAID 1 arrays but it might be a ...
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6 votes

Can ZFS mirror a single disk pool automatically?

Yes, adding a second drive to mirror an existing vdev is pretty easy. Lets say you created your pool like this. I use GPT partition labels like zfs-d1 to make the names nice/reliable. zpool create ...
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  • 128k
5 votes
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Converting Non-Raid to Raid

Converting a live boot/root disk to RAID is a lot of magic and usually it is not worth the effort. You are better off with moving to the new disk first. Start it up as a degraded raid-1, copy the ...
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  • 254
5 votes

mdadm: Which disk is being rebuilt?

When an actual rebuild is being performed, the output of mdadm --detail shows which disk is active and which disk is being rebuilt (at the bottom): # mdadm --detail /dev/md4 /dev/md4: Version ...
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  • 171
5 votes

Should I 'run in' one disk of a new RAID 1 pair to decrease the chance of a similar failure time?

It may be better to use different brands or series of disk together if you're worried about this. I have seen disks of similar type and age fail in clusters, so IMHO it's not an urban leend.
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