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39 votes

RAID-5: Two disks failed simultaneously?

You have a double disk failure. This means your data is gone, and you will have to restore from a backup. This is why we aren't supposed to use raid 5 on large disks. You want to set up your raid so ...
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  • 8,781
37 votes

RAID-5: Two disks failed simultaneously?

Your options are: Restoring from backups. You do have backups, don't you? RAID is not a backup. Professional data recovery It's possible, though very expensive and not guaranteed, that a ...
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  • 53.2k
27 votes
Accepted

RAID-5: Two disks failed simultaneously?

After you accepted a bad answer, I am really sorry for my heretic opinion (which saved such arrays multiple times already). Your second failed disk has probably a minor problem, maybe a block failure....
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  • 4,904
25 votes

DL380 G5, RAID5, ext3, RAID Failed

I'm sorry. But this is operator error. You had two failing disks on a RAID5 array, and you removed more disks than the array could sustain. Doing this without any backups is the bigger mistake. You ...
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  • 194k
22 votes
Accepted

What's the difference between a "degraded" RAID 6 array and a "clean" RAID 5 array?

Besides whatever metadata the RAID controller uses, are there any differences between these two arrays (in terms of data layout, performance, reliability)? Yes. RAID5 uses a single, rotating parity ...
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  • 8,104
19 votes

Raid 5 Hard disk corruption

If you lose more than a single disk in a RAID 5, your array has been irreperably damaged in some way. In most cases, the data is entirely destroyed in your case if you're not an expert at recovery, or ...
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  • 6,971
18 votes
Accepted

What counts as a 'large' raid 5 array?

Designing the reliability of a disk array: Find the URE Rate of your drive (manufacturers don't like to talk about their drives failing, so you might have to dig to find this. It should be 1/10^X ...
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  • 77.2k
17 votes

replacing 3 drives out of 8 in a server

Why would you ask the internet about this? There's so much WTF here, that I don't understand where to start!! This question shows a fundamental lack of understanding of hardware, RAID arrays, ...
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  • 194k
15 votes
Accepted

Recover from a Punctured RAID array

Your system I assume is still up, so the best thing to do is make an immediate backup, dump the disks/array, rebuild, and restore from the backup. Bad blocks don't always mean your backups are also ...
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  • 14.8k
12 votes
Accepted

How do I configure RAID 5, especially stripe size, with 24 x 1.2 TB drives for CentOS 6?

Please use RAID 1+0 with your controller and drive setup. If you need more capacity, a nested RAID level like RAID 50/60 could work. You can get away with RAID 5 on a small number of enterprise SAS ...
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  • 194k
11 votes

DL380 G5, RAID5, ext3, RAID Failed

Do not power the system back on again. Shut it down, call a data recovery service. There are a number of services that allow for remote recovery of this type of failure. At this point, all you can do ...
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10 votes

What are the main points to avoid RAID5 with SSD?

I found 2 research papers about this topic: Parity update increases write workload and space utilization Introduction [...] The results from our analytical model show that RAID5 is less ...
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10 votes

RAID5 array Ready for Rebuild

This is a bit crazy... A Smart Array P600 PCI-X RAID controller (circa 2005)?!? 25 disks? RAID 5? Is this an HP MSA70 enclosure? Is probably not the HP D2700? "Ready for Rebuild" is about the worst ...
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  • 194k
10 votes

replacing 3 drives out of 8 in a server

With RAID 5 you can only lose 1 disk and have your data remain available. You have lost 3 so you will need to rebuild the RAID and then restore the data from backup. We have a canonical Q&A about ...
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  • 113k
10 votes
Accepted

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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  • 29.7k
10 votes

How do I extend a RAID5 array with storcli?

If you make a mistake, you can lose all your data. Backup first. Then continue. Use storcli /c0 show to see what drives and volumes you have. The TOPOLOGY table is a good start: TOPOLOGY : ======== ...
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10 votes
Accepted

HP P840 HDD RAID 5 many strange drive failures

You probably have an heavily punctured array, which cause an early "planned death" of the replacement disk due to failed stripe reconstruction. You can read more information here and here The ...
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  • 43.3k
9 votes

mdadm: Swapping out small hard drives for bigger ones in a RAID5, How to partition?

Current versions of md tools support replacing a device while keeping the RAID (and so, the redundancy) working. You need ability to add at least one more device the the computer but after that, you ...
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  • 6,331
9 votes

What counts as a 'large' raid 5 array?

The reason that article exists is to draw attention to Unrecoverable Bit Error Rates on HDDs. Specifically, your cheap 'home PC' disks. They typically have a factory spec of 1 / 10^14. This is about ...
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  • 3,697
9 votes
Accepted

What steps should I take to best attempt to recover a failed software raid5 setup?

You've had a double drive failure, with one of the drives being dead for six months. With RAID5, this is irrecoverable. Replace the failed hardware and restore from backup. Going forward, consider ...
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  • 108k
8 votes

Recover from a Punctured RAID array

Right this instant, do the following: Stop rotating backups or deleting old ones for this system. You want to keep all of the backups you currently have. Take a full backup of the server. Hopefully ...
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  • 17.1k
8 votes
Accepted

Windows Server Backup Error - Volumes Larger than 16.7TB cannot be protected?

OK, the reason Windows Server Backup is failing is because of the cluster size you're using on the volume. (And I'll explain exactly why that is at the end, after the important issue of your RAID ...
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  • 53.2k
8 votes

Raid 5 Hard disk corruption

So just to clarify, you had a 4-disk R5 array, you replaced 2 disks at once - is that right? will the data get rebuild automatically or do I need to do some other changes If what I'm reading you'...
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  • 99.6k
7 votes
Accepted

Extended raid 5 is not expanding

This is a bit nuts... That's too many disks for a RAID5. It's offset by the fact that you have two hot-spare drives, but damn!! However, you've already expanded the underlying Array, but not the ...
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  • 194k
6 votes

Convert linux software raid from raid5 to raid6

Make use of the --backup-file option, so in case of power loss you can continue to grow the device after a reboot and ensure no data loss. mdadm --grow /dev/md0 --level=raid6 --raid-devices=6 --...
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  • 91
6 votes
Accepted

DELL PowerEdge 2950 stuck on BIOS

Make sure to unplug any USB/external drives. They can cause the server to hang at boot in many instances.
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6 votes

Raid 5 Recovery Process

You could prepare your self to the drive failure and to very all other troubles by implementing The 3-2-1 Backup plan, my personal opinion 3-2-1 should be in each business critical environment. ...
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  • 5,606
6 votes

Why has open-iscsi two times slower writes than Samba via 10G Ethernet?

First of all, the RAID-6 is the problem because of the double parity calculation. Secondly, you can connect iSCSI target twice in MS iSCSI Initiator, enable RR or Least Queue Depth (unfortunately, ...
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  • 5,086
6 votes

Storage Spaces with Parity vs RAID 5 contoller without cache

RAID5 (just like any parity RAID, f.e. RAID6 or RAID4) has to read the data before applying writes regardless of cache or no-cache on controller. See: Read-Modify-Write Vs. Read-Construct-Write ...
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5 votes

how to determine which drive belongs to which slot on raid 5

The drive configuration and RAID metadata in HP servers is stored on the disks, not the controller. For a simple server with one RAID controller, and one drive cage and only 4 bays, you should be ...
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  • 194k

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