Ubuntu :: Slow Write Speeds On Mdadm RAID 5 Array
Mar 3, 2010
I have a 4 drive RAID 5 array set up using mdadm. The system is stored on a seperate physical disk outside of the array. When reading from the array its fast but when writing to the array its extremely slow, down to 20MB/Sec compared to 125MB/Sec reading. It does a bit then pauses, then writes a bit more and then pauses again and so on.The test i did was to copy a 5GB file from the RAID to another spare non-raid disk on the system average speed 126MB/s. Copying it back on to the RAID (in another folder) the speed was 20MB/s.The other thing is very slow several KB/s write speed copying from eSATA drive to the RAID.
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Jul 14, 2010
I set up software RAID 5 on three 7200rpm Seagate Barracudas (2x80GB, 1x40GB) with 40 GB partitions on the beginning of all three disks.Now, when I do benchmarks using the Disk Utility I get about 52 MB/s read speed on the array. This seems kinda slow considering the average read speed on each individual drive is about 48 MB/s. Also, boot up takes about 30 seconds, which is the same as when I had Ubuntu installed on just one of the 'cudas, without RAID. Now, I am I missing something? Shouldn't the read speed be more that twice as fast since it can read from all three disks?
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Aug 14, 2010
I'm running a Debian homeserver, with a 3-disk (1GB each) raid 5 array using mdadm (the OS is on a separate disk).Now, smartmontools noticed some bad sectors on one of the disks, and I'm not sure what to do next (except for backup of valuable data).I found some articles on how to fix these sectors, but I'm unaware what the result on the whole array will be.
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Mar 2, 2011
a server that was running a hardware isw raid on the system (root) disk. This was working just fine until I started getting sector errors on one of the disks. So, I shutdown the system and removed the failing drive and installed a new drive (same size). On reboot I went in to the intel raid setup and it did show the new drive and I was able to set it to rebuild the raid. So, continuing the reboot everything came up just fine except the raid 1 on the system disk. I have tried many times to get the system to rebuild the raid using dmraid, but to no avail it would not start a rebuild. In order to get the system back up and make sure that the disk was duplicated I was able to 'dd' the working disk to the new disk that was installed.At present when I look at the system it does not show up with a raid setup on the system disk ( this comprises the entire 1TB disk with w partitions sda1 as / and sda2 as swap).Problem:I have decided to forego the intel raid and just use mdadm. I have a test system setup to duplicate (not the software, but the disk partitions) the server setup.
Code:
[root@kilchis etc]# fdisk -l
Disk /dev/sda: 1000.2 GB, 1000204886016 bytes
255 heads, 63 sectors/track, 121601 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
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Sep 10, 2010
I have a 7-drive RAID array on my computer. Recently, my SATA PCI card died, and after going through multiple cards to find another one that worked with linux, I now can't assemble the array. The drives are no longer in the order they were in previously, and mdadm can't seem to reassemble the array. It says there are 2 drives and one spare, even though there were 7 drives and no spares. I know for a fact that none of the drives are corrupted, because one of the non-working RAID cards was still able to mount the array for a short period, but would loose the drives during resyncing (I later found out that the chipset on the card was had extremely limited linux support). I have tried running "mdadm --assemble --scan" and after the drive is partially assembled, I add the other drives with "mdadm --add /dev/md0 /dev/sdc1". These both return errors and will not complete on the new raid card.
Code:
aaron-desktop:~ aaron$ sudo mdadm --assemble /dev/md0
mdadm: /dev/md0 assembled from 2 drives and 1 spare - not enough to start the array.
[code]....
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Dec 21, 2010
I have been having some odd issues over the last day or so while trying to get a raid 5 array running in software under Kubuntu. I installed 3 1TB drives and started up, my sd* order got all messed up( sda was now sdc and so on). This wasn't entirely unexpected, so I fixed up fstab and booted again. I found all three of the drives I installed, set them to raid auto-detect and used mdadm to create /dev/md0. I then created mdadm.conf by piping the output of mdadm --detail --scan --verbose into /etc/mdadm.conf.At this point, everything was still going swimmingly. I copied over a few hundred GB of data from another failing drive and everything seemed ok. I went to reboot once the copy was done and everything just went weird. All of the sd* drives went back to the original. Of course, this meant that the mdadm.conf was wrong. I tried to just change the device list, but that didn't work. I then deleted mdadm.conf and rebooted. The drive list stayed in the original order this time, so I just tried manually starting the array.
By erasing the partition table of the 3rd drive, I've been able to get it to the status of spare, but it says it is busy when I try to add it to the array. A grep through dmesg makes me think that md has a lock on it. I'm not sure where to go with it now. If anyone has any pointers, I would like to hear them.
Device List(original):
/dev/sda => boot drive, /home /
/dev/sdb => 1.5TB media storage, failing
[code]...
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Nov 16, 2009
mdadm --create /dev/md1 --level=1 --raid-disks=2 missing /dev/sdb1and I getmd1: raid array is not clean -- starting background reconstructionWhy is it not clean?Should I be worried?The HD is not new it has been used in before in a raid array but has beenrepartitionated.
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Jun 7, 2011
I have 4 WD10EARS drives running in a RAID 5 array using MDADM.Yesterday my OS Drive failed. I have replaced this and installed a fresh copy of Ubuntu 11.04 on it. then installed MDADM, and rebooted the machine, hoping that it would automatically rebuild the array.It hasnt, when i look at the array using Disk Utility, it says that the array is not running. If i try to start the array it says :Error assembling array: mdadm exited with exit code 1: mdadm: failed to RUN_ARRAY /dev/md0: Input/output error
mdadm: Not enough devices to start the array.I have tried MDADM --assemble --scan and it gives this output:mdadm: /dev/md0 assembled from 2 drives - not enough to start the array.I know that there are 4 drives present as they are all showing, but it is only using 2 of them.I also ran MDADM -- detail /dev.md0 which gave:
root@warren-P5K-E:~# mdadm --detail /dev/md0
/dev/md0:
Version : 0.90
[code]...
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Feb 3, 2011
When we assemble a raid array, from where does it load configuration information for that array? I thought it refers to /etc/mdadm.conf file, but in my system, mdadm.conf file doesn't even contain all information. Still it is able to successfully assemble previously created device.
# cat /etc/mdadm.conf
DEVICE /dev/sd[bcdjkl]1
DEVICE /dev/loop[012345]
[code]...
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Jul 15, 2010
I've been having troubles with software raid. In particular, the raid array becomes un "assembleable" after reboots. The config is CentOS 5, 4 sata discs (one by 160 containing OS, no raid and 3 2TB disks configured as a RAID 5 array - no spare drive). These drives were configured in anaconda and all seemed to go well (the drive and its lvm partitions worked and it finished rebuilding overnight). A couple of reboots later the drives cannot be assembled anymore and the machine won't boot. The error message says:
mdadm: /dev/md0 assembled from 1 drive and 1 spare - not enough to start the array.
Of course there are 3 drives and no spares in the array as configured. Manually starting the array with mdadm --assemble --scan gives the same message as does assembling the drive by specifying the individual parts. /proc/mdstat does recognize the 3 drives and when I look at the partition tables in fdisk, they show as being software raid. What could be wrong or steps to diagnose? I tried configuring the raid drives manually before going the anaconda route. Also, does anyone know I can edit the /etc/fstab file to disable them so the machine will at least boot. The (Repair filesystem) shell has the / drive mounted r/o.
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Mar 12, 2010
I've recently started having an issue with an mdadm RAID 6 array that been operational for about 2500 hours.
Intermittently during write operations the array stalls, dropping to almost 0 write speed for 10-30 seconds. When this occur one or both of the 2 drives attached to a 2 port Silicon Image si3132 SATA-II controller "locks up" with its activity light locked on. This just started occurring within the last week and didn't seem to coincide with any update that i noticed. The array has just recently passed 12.5% full. The size of the write does not seem to make any difference and it seems completely random. Some times copying a 5 GB dataset results in no slow down other times a torrent downloading to the array at 50kb/sec does cause a slow down and vise versa.
The array consists of 8 WD 1.5TB drives, 6 attached to the ICH9R south bridge, and 2 attached to a si3132 based PCI express card. The array is formatted as a single ext4 partition.
Checking SMART data for all drives shows no errors. Testing read speed with hdparm reports what i would expect (100mb/sec for each drive, ~425mb/sec for the array).
The only thing i did notice is that udma6 is enabled for all the ICH9R drives while only udma5 is enabled for the si3132 drives. Write cache is enabled for all the disks. Attempting to set the si3132 drive to udma6 results in an IO error from hdparm.
The si3132 drive is using the sata_sil24 driver. Nothing of interest appears in the kern or syslog. During this time top shows very high wait time.
The s13132 controller appears to have the original firmware from 2006 loaded, there are some firmware updates available on the Silicon Image website for this controller that now appear to offer separate firmwares for RAID operation (some sort of hybrid controller/software thing the controller supports) and a separate firmware for standard IDE use.
Has anyone had similar issues with this controller? Is a firmware update a reasonable course of action? If so which firmware is best supported by the linux driver?
I know i'm not using its raid features but i've dealt with controllers that needed to be in raid mode for ahci to be active and for linux to work well with them. I'm bit ify at the idea of just trying it and finding out as it could knock 2 disks of my array out of action.
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Oct 27, 2010
We have some servers that run in very harsh environments (research vessel) that need to have high-availability.We have software RAID 1 for some measure of resiliency, along with proper data backups (tapes etc), however we would like to be able to break out a new server and re-image it (including RAID setup) from a known good copy if the hardware completely fails on the production box. Simplicity of the process is a big plus.I am interested in any advice on the best way to approach this. My current approach (relatively new to Linux administration, totally new to MDADM) is to use DD to take a complete gzipped copy of one of the RAID'ed devices (from a live CD): ode:
dd if=/dev/sda bs=4096 | gzip -c > /mnt/external/image/test.img then reverse the process on the new PC, finally using Code:mdadm --assemble to re-create and re-build the array.
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Nov 30, 2010
I am learning software raid 1 with centos 5.5. I created the raid with out any problems and removed the first drive to check there was no problems and it booted. I have installed the old drive back in the system as hdc and need to resync the drives (used old drive as partitions correct) I thought I could use raidhotadd but id does not seem to exist anymore. how I resync the drives in the array hda primary and hdc secondary using mdadm
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Feb 20, 2011
This is message I get when I try and start itmdadm: /dev/md0 assembled from 2 drives - not enough to start the arrayBelow is the information I've collected about any help on how I can get the raid back up and going to I can get the data off of it would be awesome
sudo mdadm --examine --scan -v
ARRAY /dev/md0 level=raid10 num-devices=4 UUID=91c36708:a7cbb532:5b51dc92:ba008491
devices=/dev/sdd1,/dev/sdc1,/dev/sdb1,/dev/sda1
[code]...
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Aug 31, 2010
I have been having this problem for the past couple days and have done my best to solve it, but to no avail. I am using mdadm, which I'm not the most experienced in, to make a raid5 array using three separate disks (dev/sda, dev/sdc, dev/sdd). For some reason not all three drives are being assembled at boot, but I can add the missing array without any problems later, its just that this takes hours to sync. Here is some information:
[Code]....
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Oct 11, 2010
I'm trying to back up my hard drive to a 2 TB WD external so that I can do a clean install of 10.10, however I'm getting tremendously slow write speeds. It hovers around 1.5 MB/s and steadily slows from there. It tells me it will take 150+ hours to transfer 400 GB of data.
I have a AMD quad core processor and 8 gigs of ddr3 ram... USB 2.0... I feel this should go much faster.
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May 31, 2011
I've been having some problems w/ a my RAID 5 array, and after extensive investigation, I'm fairly sure that my last resort is rebuilding the array. I'd tried --assemble, b/c it's a previously created array, but it didn't seem to like that. So, I checked into --create, and it will re-create the array w/out destroying the data, if the superblocks are persistent, which they seem to be. However, here's what I get:
[Code]....
My question is: why do /dev/sdb1 and /dev/sdi1 show as both ext2fs and also as part of a RAID array?
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Sep 7, 2010
I'm currently experiencing some serious issues with WRITE performance on a RAID-1 array. I'm running Ubuntu 10.04 64 bit server with the latest updates. To evaluate the performance ran the following test: [URL]... (great article btw!) Using dd to measure, write performance is only at 8.7 MB/s. Read is great though at 74.5 MB/s. The tests were ran straight after rebooting and I have not (YET!) done any kernel tuning or customization, running the default server package of the Ubuntu kernel. Here's the motherboard in the server: [URL]... with a beta bios to support drives over 300GB.
[code]...
As you can see from the bo column there is definitely something stalling. As per top output, the %wa (waiting for i/o) is always around %75 however as per above, writes are stalling. CPU is basically idle all the time. Hard drives are quite new and smartctl (smartmontools) does not detect any faults.
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Mar 18, 2010
I wonder how to attach new sata hard disk to software array where are two disk and one is crashed (this is a mirroring mode=Raid 1).Situation like this:I unpluged crashed disk and I buy the similar one and plug in What Next should I do?
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Jan 5, 2011
I have recently migrated my file server over to a HP Microserver. The server has two 1TB disks, in a software RAID-1 array, using MDADM. When I migrated simply moved the mirrored disks over, from the old server Ubuntu 9.10 (server) to the new one 10.04.1 (server).I Have recently noticed that write speed to the RAID array is *VERY* slow. In the order of 1-2MB/s order of magnitude (more info below). Now obviously this is not optimal performance to say the least. I have checked a few things, CPU utilisation is not abnormal (<5%) nor is memory / swap. When I took a disk out and rebuilt the array, with only one disk (tried both) performance was as to be expected (write speed >~70MB/s) The read speed seems to be unaffected however!
I'm tempted to think that there is something funny going on with the storage subsystem, as copying from the single disk to the array is slower than creating a file from /dev/zero to the array using DD..Either way I can't try the array in another computer right now, so I though I was ask to see if people have seen anything like this!At the moment I'm not sure if it is something strange to do with having simply chucked the mirrored array into the new server, perhaps a different version of MDADM? I'm wondering if it's worth backing up and starting from scratch! Anyhow this has really got me scratching my head, and its a bit of a pain! Any help here would be awesome, e-cookies at the ready! Cheers
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Nov 22, 2009
Here's a brief description of my system:
120GB Sata HDD - Primary OS drive
3 x 1.0TB Sata HDD - Raid 5 array
This is on a C2D MSI P35 Platinum board. Anyway, did a fresh install of F12 on the 120GB, which I had problems with - Anaconda refused to see the drive. Fedora Live could see it fine, and it was listed as an 'nvidia_raid_member' - no idea why, but I completely erased the disc under the Live CD and proceeded to install F12.
Once F12 was installed, I loaded up mdadm to re-activate my Raid 5 array, using 'sudo mdadm --assemble --uuidthe uuid) - and it started with only 2 of the 3 drives. My /dev/sdb drive did not activate into the array, due to what mdadm said was a mismatched UUID. Ok, so I erased /dev/sdb, intending to rebuild the array. Erased /dev/sdb, and then attempted 'sudo mdadm --add /dev/md0 /dev/sdb' and I get this error: "mdadm: Cannot add disks to a 'member' array, perform this operation on the parent container" - I can find NO information on this error message.
[Code].....
I don't believe the hard drives are connected in the exact same order they were in before - I disconnected everything in the system and blew it out (it was pretty dusty)
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Apr 17, 2011
Whenever I transfer a movie into my 16GB USB flash disk, my whole system becomes windows-like and unusable!
When i drag the file(s) into the USB disk folder, it starts out fine and pretty darn fast (25mb/sec) then slowly decreases until it's unbearably slow (3m/sec) and as a side effect my whole system starts deteriorating. I basically have to wait for the file to finish transferring before i can use my desktop again!
This has been happening with every version since Karmic (all 64bit)- I put up with it because I don't use the USB stick that much.. but lately it's been my go to source for transfering large files to/from work.
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Jan 11, 2010
I am planning on setting up a 4x1TB RAID5 with mdadm under Ubuntu 9.10. I tried installing mdadm using "sudo apt-get install mdadm", all worked fine except for the following error: Code: Generating array device nodes... /var/lib/dpkg/info/mdadm.postinst: 170: /dev/MAKEDEV: not found failed. The end result is the /dev/md0 device has not been created, as can be seen here:
Code: windsok@beer:~$ mdadm --detail /dev/md0 mdadm: cannot open /dev/md0: No such file or directory After googling, I found the following bug which describes the issue: [URL] However it was reported way back in April 2009, and it does not look like it will be fixed any time soon, so I was wondering if anyone knows a workaround for this bug, to get me up and running?
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Jul 18, 2011
I have a raid5 on 10 disk, 750gb and it have worked fine with grub for a long time with ubuntu 10.04 lts. A couple of days ago I added a disk to the raid, growd it and then resized it.. BUT, I started the resize-process on a terminal on another computer, and after some time my girlfriend powered down that computer!
So the resize process cancelled in the middle and i couldn't acess any of the HDDs so I rebooted the server.
Now the problem, the system is not booting up, simple black with a blinking line. Used a rescue CD to boot it up, finised the resize-process and the raid seems to be working fine so I tried to boot normal again. Same problem. Rescue cd, updated grub, got several errors: error: unsupported RAID version: 0.91. I have tried to purge grub, grub-pc, grub commmon, removed /boot/grub and installed grub again. Same problem.
I have tried to erased mbr (# dd if=/dev/null of=/dev/sdX bs=446 count=1) on sda (ide disk, system), sdb (sata, new raid disk). Same problem. Removed and reinstalled ubuntu 11.04 and is now getting error: no such device: (hdd id). Again tried to reinstall grub on both sda and sdb, no luck. update-grub is still generating error about raid id 0.91 and is back on a blinking line on normal boot. When you'r resizeing a raid MDADM changed the ID from 0.90 to 0.91 to prevent something that happend happened. But since I have completed the resize-process MDADM have indeed changed the ID back to 0.90 on all disks.
I have also tried to follow a howto on a similar problem with a patch on [URL] But I cant compile, various error about dpkg. So my problem is, I cant get grub to work. It just gives me a blinking line and unsupported RAID version: 0.91.
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Sep 27, 2010
I have a NETGEAR ReadyNAS NV+ with four 1TB drives in a RAID-5 array. This is our primary file storage. This has previously been backed up to a hardware RAID-0 array directly attached to our Windows server. The capacity of this backup array is no longer sufficient. So the plan was, take a bunch of 200GB to 320GB drives (And a 750) I had kicking around, chuck them in a couple of old SCSI drive enclosures I have collecting dust, attach them via IDA/SATA-to-USB adaptors to a USB hub, attach that to the server, create a JBOD array spanning the disks, and back up the NAS to that. Performance is not an issue as this is just to be used for backup, with the idea being as near to zero cost as possible (Spend so far = NZ$100�ish).
The first hurdle I struck was Windows not supporting Dynamic Disks on USB drives (Required to create a spanned volume). At first I resisted using another machine (i.e. a machine running Ubuntu) as I didn't want to dedicate a piece of hardware to backing up the NAS. I then decided it would be acceptable to do this via a VM, which is what I've done.So I have 10.04 running under VMWare Server 2.0.2 under Windows Server 2008 R2. The disks are all presented to the VM. I wasn't sure if I was going to end up creating the array under LVM or something else, but I noticed Disk Utility has an option to create an array, so I tried that. When I add two 250GB drives, the array size is 500GB. When I then add a 160GB drive, the array size drops to 480GB. Huh? If I keep adding disks (Regardless of order) the final array size comes out at 1.8 TB, as per the attached screenshot. Now with the following drives, I expected something more like:
160 + 250 + 250+ 750 + 250 +200 + 200 + 250 + 320 + 250 + 320 = 3.2TB
Am I missing something or making a false assumption somewhere?
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Mar 30, 2010
I tryed to install ubuntu 10.04 using the beta alternative install cd.
Everything went fine until the partitioning section.
I choose manual partitioning and all my existing partitions were detected correctly included my 2 mdadm raid0 arrays.
I choose md0 as my / partition and choose to format the partition
I choose md1 as my /home partition as choose to keep the data
When I choose to continue and write the changes to disk the install started to create an ext4 partition on md0, the installer then stopped with an error that the kernel could not reread the partition table.
I aborted the installation at this point.
Now I can not access either of my arrays.
I have booted a livecd and installed mdadm. When I checked /etc/mdadm/mdadm.conf my existing arrays were already listed.
Code:
# mdadm.conf
#
# Please refer to mdadm.conf(5) for information about this file.
#
[Code].....
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Jul 31, 2010
I had a raid array working great in 9.04 with mdadm, and I just recently upgraded to 10.04 (clean install) and I'm trying to reassemble the array and having a dickens of a time.When I try to recreate the array with:
Code:
sudo mdadm --create /dev/md0 --level=5 --raid-devices=3 /dev/sdb /dev/sdd /dev/sdc
I get this:
[code]....
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Apr 10, 2011
I have created a RAID 5 array using the built in Disk Utility.This is great and formatted it with ext4, and mounted it.However on reboot in Disk Utility as RAID Array is not running and under state Not running, partially assembled.I have to stop the array then restart it, then mount it before I can access what is on it.Obviously this is not very good as I often have the system shutdown at night to converse energy, and having to do this every time it boots is a pain.Could someone please explain in plain english what I need to go to get my array to start and mount on startup
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May 21, 2011
trying to troubleshoot an issue i'm having with MDADM I have a raid 5 array consisting of 5 2tb Western Digital Green drives. It has been working fine for the last 6-7 months but recently has stopped working. After rebooting i get an error something like "unable to mount /mnt/storage" which is the filesystem on the raid array the raid array is /dev/md0 when i do a " sudo mdadm --assemble --scan" i get the error mdadm: /dev/md0 assembled from 3 drives - not enough to start the array all the drives are there and i can see the correct partition information if i load them up in parted.
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Jul 27, 2010
after a failed upgrade from 9.10 to 10.04 I had to format my computer and do a clean install of 10.04, and now my mdadm raid5 array wont start.my array is called "The Library", and i believe the space between "The" and "Library" is causing the command disk utility uses to start the array to fail.The exact error isAn error occurred while performing an operation on "The Library" (RAID-5 Array): The operation failed
Error assembling array: mdadm exited with exit code 1: mdadm: unrecognised word on ARRAY line: Library
mdadm: unrecognised word on ARRAY line: Library
[code]....
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