General :: Raid - RAID1 With Only One Disk
Oct 27, 2010
I have a hypothetical situation in which I installed my operating system using a RAID1 mirror. At some point I decided that this setup was overkill, my machine isn't system critical, I value doubling my storage space more than speedy recovery, I'm doing routine backups, etc...
Short of backing up my system volume and repartitioning, or otherwise starting over, is there a way I can reconfigure my RAID1 array to only expect one disk so that mdadm no longer reports a Degraded state?
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Feb 14, 2011
I've got a couple of commercial NAS boxes and I'm wondering if they (ReadyNas duo, DLink DNS-323) or any other NAS is suitable for having their RAIDed disks moved to a software-based NAS. To be specific, I'm a big fan of the (largely) Debian-based Ubuntu. Can the aforementioned NAS drives be migrated to Ubuntu (e.g. using the mdadm Linux command)?
Secondly, is there any commercial NAS that can be migrated over? Incidentally, here is a link to somebody who succeeded in a migration:URL...My specific scenario I'd like to prepare for, is the eventual (sudden) death of one of the NAS motherboards.
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Jun 8, 2011
Is there a difference between raid1 and ordinary hard disk?
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Jun 9, 2010
I have two 80 GB IDE hard disk. I have create raid1 partition in both drive using [URL] ink. raid is working fine. But i have copy some data on one hard disk (md0) but this data is not autometically copy in second hard disk(md1). I want when data is write on one hard disk, this data autometically write in second hard disk.
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Dec 7, 2010
Just finished installing F14 with RAID1 setup for 2 hdd (SATA''s). Entire drives are mirrored, including SWAP. As I had done in the past, I was planning on installing grub on MBR of 2nd hdd. In prep for this I did the following to locate the grub setup files:
grub> find /grub/stage1
find /grub/stage1
(hd0,1)
[code]....
I was surprised, expected to get (hd0,0) & (hd1,0), not (hd0,1) & (hd1,1)
running "fdisk -l" I get:
Disk /dev/sda: 120.0 GB, 120034123776 bytes
255 heads, 63 sectors/track, 14593 cylinders, total 234441648 sectors
Units = sectors of 1 * 512 = 512 bytes
[code]....
MBR is the first 512 bytes of the drive. Each partition has a boot sector. In my case grub stage 1 is on 2nd partition of sda & 2nd partition of sdb. What i dont understand is how grub stage 1 can be on sda2 & sdb2, since I am assuming that sda1 & sdb1 would be the first partitions of the drives & therefore contain the MBR's. Maybe this might be because sda1 & sdb1 are SWAP partitions?
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Apr 5, 2011
I recently had an issue where one of my RAID1 configured drives died on a Debian box. By die, I mean after post, I am presented with a black screen and flashing cursor, nothing more. I booted into a knoppix shell and did:
mdadm --assemble /dev/md0 --run -u <UUID of the only working drive> /dev/sda1
I could then 'mount /dev/sda1 /mnt/' and see all the contents as I should be able to. However, I cannot boot from this device by itself for some reason. I have reinstalled grub 'grub-install --recheck --rootdirectory=/mnt /dev/sda1' #something like that, can't remember the exact --rootdirectory command without the switch. I restarted, with the failed drive unplugged, and again, I'm faced with the black screen, flashing cursor.
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Aug 4, 2010
I want to build a 6xSATA RAID 5 system with on of the disks as spare disk. I think this give me a chance of 2 of 6 disks failing without losing data. I am right?
Hardware: Intel ICH10R
First I will creat a 3xSATA RAID 5, after I will add the spare disk and after that I will add the others disks. This is what I think I should do.
Step 1:
Create RAID Device
Code:
mdadm --create --verbose /dev/md0 --metadata 1.2 --level=5 --raid-devices=3 /dev/sda1 /dev/sdb1 /dev/sdc1
I read that "--metadata 1.2" is the best option. It is true?
Create filesystem on the RAID device
Using this method of calculation:
* chunk size = 128kB (for RAID 5)
* block size = 4kB (recommended for large files, and most of time)
* stride = chunk / block = 128kB / 4k = 32kB
* stripe-width = stride * ( (n disks in raid5) - 1 ) = 32kB * ( (5)- 1 ) = 32kB * 4 = 128kb
Then:
Code:
mkfs.ext3 -v -m .1 -b 4096 -E stride=32,stripe-width=128 /dev/md0
Step 2:
Add spare-disk
Code:
mdadm --add /dev/md0 /dev/sdd1
Is this enough?
Step 3:
Adding disks:
Code:
mdadm --add /dev/md0 /dev/sde1
mdadm --grow /dev/md0 --raid-devices=4
fsck.ext3 /dev/md0
resize2fs /dev/md0
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Aug 12, 2010
I just configured two raid setups but after a reboot they are not mounted and seem to be inactive.
md127 = sde1, sdf1 and sdi1 (raid 5)
md0 = sda1 and sdh1 (raid 0)
Code:
root@server /]# cat /proc/mdstat
Personalities :
md127 : inactive sdf1[1](S) sde1[2](S)
78156032 blocks
md0 : inactive sda1[0](S)
488382977 blocks super 1.2
unused devices: <none>
Code:
[root@server /]# fdisk -l | grep "Disk /"
Disk /dev/sda: 500.1 GB, 500107862016 bytes
Disk /dev/sdb: 80.0 GB, 80026361856 bytes
Disk /dev/sdc: 122.9 GB, 122942324736 bytes
Disk /dev/sdd: 160.0 GB, 160041885696 bytes
Disk /dev/sde: 40.0 GB, 40020664320 bytes
Disk /dev/sdf: 40.0 GB, 40020664320 bytes
Disk /dev/sdg: 1500.3 GB, 1500301910016 bytes
Disk /dev/sdh: 251.0 GB, 251000193024 bytes
Disk /dev/sdi: 40.0 GB, 40020664320 bytes
Disk /dev/sdj: 500.1 GB, 500107862016 bytes
Code:
[root@server /]# cat /etc/mdadm.conf
DEVICE /dev/sdi1 /dev/sdf1 /dev/sde1 /dev/sda1 /dev/sdh1
ARRAY /dev/md127 UUID=5dc0cf7a:8c715104:04894333:532a878b auto=yes
ARRAY /dev/md0 UUID=65c49170:733df717:435e470b:3334ee94 auto=yes
As you can see they now show up as inactive. And for some reason sdi1 and sdh1 are not even listed. What can I do to get them back? To make matters worse I placed some important data on them, and even if I was clever enough to keep an extra copy on another drive, guess which drive that was? So, I need to get them activated as is (at least so I can get the data of them) before I can rebuild them from scratch. I'm running Mandriva 2010.1 and rated tehm using the built in disk partitioner.
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May 5, 2010
I have an Ubuntu Server on (8.10) running under Citrix XenServer (though that shouldn't make a difference).
I installed on a single disk:
xvda1 - 200 MB - /boot
xvda2 - 9.8 GB - LVM (ubuntu-base)
The LVM is:
swap - 1.0 GB
root - 8.8 GB - /
I have successfully gotten this converted to RAID1 by adding a new drive (xvdb) and following the Debian howtoforge article [URL]
What I have not been able to do, is get grub working properly.
If I fail xvdb and reboot the system, everything comes up and I can reboot and run.
If I fail xvda and reboot the system, XenServer gives me a bootloader error. i.e.: no grub
If someone has done this, can they tell me what grub commands to run to get a successful boot of the primary disk fails?
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May 3, 2011
im on 10.10(desktop) and mdadm was v2.8.1 from 2008, very out of date so i tried 3.2.1 -> no change. mdadm raid1 read speeds are the same as single disk. note i used the tests in the disk utility benchmarking tool at first --these showed raid 5 atleast to be much better but when i tried dd reads raid5 dropped off with larger data to almost the same (slow) speed as raid1. compare:
[code]....
using two partitions will be enough to show raid1 performs at single disk speed. I dont really want to use a 4 disk raid0 just to get the read speed i should be able to get with raid1 as i dont really care about the size loss. I would of course use raid10 but i have found this suffers from the same problem (achieve same read speed as 2 disk stripe). So whilst im shocked others aren't reporting this, unless there is some obscure reason why my system would give these results i think raid1 in not behaving as it should.
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Nov 3, 2010
Purchased (4) 2TiB Drives (actual disk space) and created a RAID5 array expecting to have 6TB of useable disk space, however actual useable space is 5.46TiB.
So, the question is where did the disk space go?
First off, I can say for certainty the disks actual useable is verified at 2TB each have mounted and formated on a non-linux system (OSX).
Disks - 2TB Per disk, Tested HFS, Actual 2TB Useable
root@server:/server# fdisk -l 2>/dev/null | egrep "sd[hijk]" | grep Disk
Disk /dev/sdh: 2000.4 GB, 2000398934016 bytes
Disk /dev/sdj: 2000.4 GB, 2000398934016 bytes
Disk /dev/sdk: 2000.4 GB, 2000398934016 bytes
[Code]....
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Mar 15, 2011
I newly installed debian squeeze with software raid. The way I did was, as also given in this thread.
- I have 2 HDD with 500 GB each. For each of them, I created 3 partitions (/boot, / and swap)
- I selected the hard drive and created a new partition table
- I created a new partition that was 1GB. I then specified to use the partition as a Physical Volume for RAID. and used for /boot and enabled bootable.
- Created another partition, which is of 480 GB, and then specified to use the partition as a Physical Volume for RAID. and used for /.
- Created another partion and used for swap
Then RAID configuration:
Through Configure RAID menu -> create MD device ->
(2 for the number of drives, 0 for spare devices)
Next select the partitions you want to be members of /dev/MD0. I selected /dev/sda1 and /dev/sdb1 (for /boot)
Next select the partitions you want to be members of /dev/MD1. I selected /dev/sda6 and /dev/sdb6 (for /)
And no RAID for swap partitions
'Finish Partitioning and write changes to disk' --> Finish the rest of the install like normal. Everything is ok now, except I am not sure how to test my raid config. When I pull the power of the HDD, it only boots from one disk. I read in some forum that I may have to install GRUB manually on the other. In Debian Squeeze, there is no grub command. Not sure how to make my software raid bootable from both disk. I configured /boot partitions of both disks to be boot=yes. Not sure whether that is ok.
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Apr 4, 2010
I have installed a Fedora Core 12 Linux system onto a RAID 1 file system. I now need a way of getting an notification if the disk fails. Is there an SNMP MIB that covers Intel RAID? I have done the searching but still the answer alludes me.
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Dec 12, 2009
I have a 5 disk raid 5 array that is composed of SATA A:0,1; SATA B: 0,1, and SATA C:0, and one of the disks (SATA A:0) recently went bad on me. I have an ICP raid controller that is about 5 years old. I replaced SATA A:0. After rebooting, I went into the controller and verified that it saw the disk in the hard-disk info section...there I noticed that in the "status" section, that the SATA C:0, SATA B:1 disks were listed as being "in array", the SATA A disks were blank, and the SATA B:0 disk was listed as "fragment". When I go into the "repair array" section, the controller tells me that there are no arrays that are in failure, error, or need to be rebuilt.
This puzzles me, as I thought the controller would know that the array needs to be rebuilt after replacing the disk and I don't see a way to initiate a rebuild. If I just let the server boot after replacing the disk, then I get back that there are the correct number of disks in the raid 5 and that it is ready, however, the screen then goes blank and I get a blinking cursor and the system seems to hang. There are no activity lights on any of the drives associated with the raid 5, which makes me think that the system is not rebuilding the array at this point.
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Apr 7, 2011
I am trying to create a Raid 1 ram disk. Below are the commands I used:
[root@abidbodal dev]# mke2fs -m 0 /dev/ram8
[root@abidbodal dev]# mount /dev/ram8 /mnt/rd8
[root@abidbodal dev]# mke2fs -m 0 /dev/ram9
[code]....
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Mar 12, 2011
I've read many of the postings on ICH10R and grub but none seem to give me the info I need. Here's the situation: I've got an existing server on which I was running my RAID1 pair boot/root drive on an LSI based RAID chip; however there are system design issues I won't bore you with that mean I need to shift this RAID pair to the fakeraid (which happens to most reliably come up sda, etc). So far I've been able to configure the fakeraid pair as 'Adaptec' and build the RAID1 mirror with new drives; it shows up just fine in the BIOS where I want it.
Using a pre-prepared 'rescue' disk with lots of space, I dd'd the partitions from the old RAID device; then I rewired things, rebooted, fired up dmraid -ay and got the /dev/mapper/ddf1_SYS device. Using cfdisk, I set up three extended partitions to match the ones on the old RAID; mounted them; loopback mounted the images of the old partitions; then used rsync -aHAX to dup the system and home to the new RAID1 partitions. I then edited the /etc/fstab to change the UUID's; likewise the grub/menu.list (This is an older system that does not have the horror that is grub2 installed) I've taken a look at the existing initrd and believe it is all set up to deal with dmraid at boot. So that leaves only the grub install. Paranoid that I am, I tried to deal with this:
dmraid -ay
mount /dev/mapper/ddf1_SYS5 /newsys
cd /newsys
[code]....
and I get messages about 'does not have any corresponding BIOS drive'. I tried editing grub/device.conf, tried --recheck and any thing else I could think of, to no avail. I have not tried dd'ing an mbr to sector 0 yet as I am not really sure whether that will kill info set up by the fakeraid in the BIOS. I might also add that the two constituent drives show up as /dev/sda and /dev/sdb and trying to use either of those directly results in the same error messages from grub. Obviously this sort of thing is in the category of 'kids don't try this at home', but I have more than once manually put a unix disk together one file at a time, so much of the magic is not new to me.
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Jul 22, 2011
I have SLES10-SP3 running on an Intel SR1600URHS board with 3 hot-swap SATA disks configured using mdadm as Raid1 with hot spare. If I pull one of the active disks, all file i/o will stop for about 2.5 minutes after which it will start again and the raid array will be rebuilt using the spare disk. Is there any way I can reduce this 2.5 minutes of inactivity? I've tried setting /sys/block/sdX/device/timeout and /sys/block/sdX/device/retries to 1 for all disks, but this hasn't made any difference. The output from messages is:
12:11:56: ata2.00: exception Emask 0x0 SAct 0x0 SErr 0x0 action 0x2 frozen
12:11:56: ata2.00: cmd ea/00:00:00:00:00/00:00:00:00:00/a0 tag 0 cdb 0x1e data 0
12:11:56: res 40/00:03:00:00:20/00:00:00:00:00/b0 Emask 0x4 (timeout)
[code]....
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Oct 16, 2009
my Fedora 11 system is not starting anylonger. It stops with the message:
Code:
VFS: Can't find ext4 filesystem on dev dm-0
The system told me since a while, that a lot of the sectors of one disk of the (software) RAID compound are failed already. So tried to disconnect each of the disks and start them separately. Unfortunaltly this is not working (for one its is not working at all, the other wents the same far as with both), when I tried to recover the system with the Fedora DVD, it said no distribution found. I am quite new and do not know so much about linux system, so i do not know what further information you could need. Maybe it can be important, that both disks are encryped (the system wents so far, that I can type in the password).
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Jun 28, 2010
I have an SiI hardware SATA RAID card, with two 500GB disks in mirrored RAID configuration. When I first plugged them in and set it up, things seemed to work ok, but on boot the raid controller told me that the RAID needed rebuilding, and it would happen automatically after POST. So I didn't worry about it, and the drive mounted fine, and it's been that way for years. I just went in and manually on-line rebuilt the RAID in the controller's BIOS, and now when I boot into Ubuntu, both disks show up in fdisk, but neither show up in /dev/disk/by-uuid. Am I missing something?
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Jul 7, 2011
I need to copy data from a single HD, which used to be part of a Linux RAID 1. I've googled around, but can't find any clue how to mount partitions from this single HD.
Background: The HD comes from a linux based NAS box Synology DS207+. The NAS uses ext3 as filesystem. Both NAS disks are fine, but the other NAS hardware is dead and not worth repairing or replacing.
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Dec 15, 2010
So I didn't notice when I setup my CentOS 5.5 server that I left / as RAID 0 on md1. All the rest are RAID 1. Is there a way I can modify the array to RAID 1 without a risk of data loss? I'm glad I caught this before I setup any other services. I've only setup smb so far...
[root@ftpserver ~]# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/md1 16G 3.0G 13G 20% /
[code]....
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Aug 1, 2010
I had done a new lucid install to a 1 TB RAID 1 array using the alternate CD a few weeks back. I messed up that system trying to some hardware working that lucid doesn't have drivers for yet, so I gave up on it and reinstalled to a single 80 GB disk that I now want to move over to the RAID array.
I moved all of the existing files on the array to a single folder, then copied all of the folders from the 80 GB disk over to the array with permissions and symlinks (minus the contents of /proc and /sys, which I created empty).
These are the commands I used:
Quote:
p -a -d -R -v -t /media/raid_array /b*
cp -a -d -R -v -t /media/raid_array /d*
cp -a -d -R -v -t /media/raid_array /e*
cp -a -d -R -v -t /media/raid_array /h*
[Code]....
I tried to change fstab to use the 689a... for root, but when I try to boot, it's still trying to open /dev/disk/by-uuid/412d...
So then I booted from the single disk again and chrooted into the array, then ran update-initramfs -u. I got 3 "grep: /proc/modules: No such file or directory" errors, and "cat: /proc/cmdline: No such file or directory"- so I created directory /proc/modules, created an empty file /proc/cmdline, and ran the initramfs update again. Then I tried to shut down, which hung (probably because I was doing all of this from a terminal window in Gnome), so I killed the power after a couple of minutes.
It's still trying to use /dev/disk/by-uuid/412d... to boot.
What am I missing? I assume I just have to change the UUID to mount as root, but I don't know how.
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Feb 1, 2011
We have had a hardisk crash in our RAID1 webhosting server running CentOS5 and Plesk. We first realized something was wrong when our main site didn't load but showed MySQL errors. We then found out that the system was in read-only state. Something that also happened the day before yesterday, but we could fix with a FSCK. Then the system worked well til around 18 hours later when it crashed with the same sympoms. So, we rebooted the server and wanted to do a filesystem check again. But the HDD wouldnt even load. It was gone. Unfortunatelly it was not realized that the second disk in the system was also not working any more for some time now. Fortunatelly we had our main site backed up externally though. So we could re-install a fresh box and mounted the two drives to the system. We checked the harddisk. One is practically empty (the older one), the other has almost only files in 'lost + found' but these are all "numbered", no real filenames or so.
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Jul 6, 2010
So I have a system that is about 6 years old running Redhat 7.2 that is supporting a very old app that cannot be replaced at the moment. The jbod has 7 Raid1 arrays in it, 6 of which are for database storage and another for the OS storage. We've recently run into some bad slowdowns and drive failures causing nearly a week in downtime. Apparently none of the people involved, including the so-called hardware experts could really shed any light on the matter. Out of curiosity I ran iostat one day for a while and saw numbers similar to below:
[Code]...
Some of these kinda weird me out, especially the disk utilization and the corresponding low data transfer. I'm not a disk IO expert so if there are any gurus out there willing to help explain what it is I'm seeing here. As a side note, the system is back up and running it just runs sluggish and neither the database folks nor the hardware guys can make heads or tails of it. Ive sent them the same graphs from iostat but so far no response.
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Jul 17, 2010
point me in the direction to get a step by step guide to setting up a Raid 5 using the Disk Utility and 3 spare drives? I have the main OS files on a 80gig drive and I would like to mount the 3 drives as Raid 5.Just shooting in the dark now.. Screen shot is attached. [URL]...
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Jul 20, 2011
Has anybody ever used Disk Utility to set up software RAID? Here I am running terminal commands (I'm a terminal junkie) and I just happen to stumble across instructions that indicate "Or you can just set it up through Disk Utility."
Sure enough in disk utility, it looks like all of the configurable options are there. It makes me wonder, though... is this kind of GUI functionality something that isn't really solid? Or does it operate predictably and effectively?
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May 14, 2009
I am working on:
SUSE Linux Enterprise Server 10 (ia64)
VERSION = 10
PATCHLEVEL = 2
Example 1: If Raid is enabled on disk then the information in cat /proc/partitions is shown as :
104 0 35532720 cciss/c0d0
104 1 2104483 cciss/c0d0p1
104 2 33423232 cciss/c0d0p2
104 16 35532720 cciss/c0d1
104 32 35532720 cciss/c0d2
Example2: If normal disk is taken the output is as follows:
8 0 35566480 sda
8 1 102383 sda1
8 2 409600 sda2
8 3 210925 sda3
8 4 2104515 sda4
8 5 32739023 sda5
According to my application I need to find out the information of the disk. How can I get disk information when my system is RAID enabled(cat /proc/partitions shows the entry of the controllers in example 1). Can we get Partitions information of the Disk when Disk are connected to system by controller?
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Sep 21, 2010
I have a IBM x306 server with on board RAID1 controller. One of the two disk is dead, I need to replace it. I'm using the "ServRaid Manager" to reconfigure the array. I shut down the server and replaced the dead disk with new one, I first started the server and not doing anything manually - thinking that it will auto sync, but it just didn't! I then re-started the server and logged in with ServRaid Manager. Now I want to reconfigure the array so that the new disk will sync. But the problem is that in this arrays property, the "Synchronize" option is grayed out, I just cant click on it! On the other hand on the newly inserted disk's property I was able to click "re-build", but after this, things just stopped there, its not synchronizing. How do I simply replace this new disk and have things working?
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Jul 15, 2010
I have a system with data stored in multiple disk arrays. I have to come up with a solution that will maintain the disk order of the arrays whenever a stripe fails, is removed and then put back in. One solution I came up with was to stamp every stripe with the disk array it belongs to along with its stripe id. I plan to put this stamp in the last 512 KB of each disk. And I maintain all this information in a sqlite database, that is disk array, stripe id, the software diskname, etc. So that whenever a disk is replaced, its stamp could be read and the corresponding entries in the database are updated.
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Jun 9, 2011
Following scenario: My server in some data center on a different continent with two disks and software raid 1.
One day I see that a disk failed (for example with /proc/mdstat). Of course I should replace the failed disk asap. Now that I think about it, I am not sure how. What should my email to the data center support guy mention to make sure that guy doesn't replace the wrong disk?
With hardware RAID it is very easy, because the controller usually has some kind of red LED indicator. But what about software raid?
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