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Can a mirrored (RAID-1) disk be plugged into another system to be read?

If I have disks in a RAID-1 array, can I take one of them out and plug it into a different system to be read?

This means, on the target system, treating the disk from the RAID array just like an ordinary disk, regardless of any controller/driver support and without doing any rebuilding.

The idea is that if my array (of 2 disks) degrades, I can plug it into a different system and don't have to get another disk of the same capacity (which gets harder as time passes) and (hopefully) even without access to the original system, in the event that the controller or motherboard goes bad instead of one of the disks.

Does RAID1 increase performance with Linux mdadm?

I have a cheap 2-bay NAS with a 2TB HDD. To be robust against disk failure, I'm thinking of buying a second 2TB HDD and putting it in RAID1 with Linux mdadm. The file system is ext4.

Will this increase or decrease the performance of the NAS? What about just read or write performance?

There seem to be lots of opinions about this online but no consensus.

Thanks.

Edit:

So already I've got three different answers: "a fair bit faster", "you wont notice" and "will decrease the performance if anything". (I am interested primarily in read performance.) Wikipedia says "the read performance can go up roughly as a linear multiple of the number of copies". Which one is it?

Edit 2:

I've found mounting evidence in support of RAID1 increasing read performance, including the MD manpage:

Changes are written to all devices in parallel. Data is read from any one device. The driver attempts to distribute read requests across all devices to maximise performance.

I also discovered MD's RAID10 with --layout=f2, which provides redundancy of RAID1 with the read performance of RAID0, and can be used with just two drives. The write performance is reduced however, as a sequential write involves both drives seeking back and forth between distant parts of the drive. man md for details.

Upgrading disks in a RAID1 Synology 2-bay drive

I have a Synology 2-bay 211j NAS with 2x1TB HDD installed as single RAID 1 volume. I'm running out of space, so I'd like to upgrade my NAS with 2x3TB HDDs. Is there any easy way to copy all data from the earlier 1TB volume(s) to the new 3TB RAID1 configuration, without utilizing extra backup devices or additional NASs?

What exactly does a RAID 1 resync do?

I just have a quick question about RAID 1 resyncs. When a RAID 1 array performs a resync is it actually copying all the data from one disk to another or is it just analyzing the data on the disks and correcting any differences?

The reason I ask is because I have a RAID 1 array on my laptop HDD with two external HDD's and whenever I take it anywhere I disconnect the externals. This causes a resync when I plug them back in and I don't want to be putting unnecessary stress on the drives if a resync does, in fact, copy all the data again. Thanks for any info!

Btrfs RAID1 SSD + non-SSD

My laptop has two disks, a SSD and a traditional magnetic disk. I plan to make a partition on the mag disk equal in size the SSD and set up BTRFS RAID1. This I know how to do.

The only reason I'm doing the RAID1 is for the self-healing. I realize writing large amounts of data will be slower that the SSD alone, but is it possible to set it up to only read from the magnetic drive if there's an error reading from the SSD?

How to fix missing RAID1 drive

I had to do some fiddling about with my cables inside thebox and now I am getting a "Critical Error" about the RAID disks during startup. I have a gigabyte GA-MA770T-UD3 motherboard. Aparently the RAID controller is an AMD SB710 chip.

I'm pretty sure I know what happenned. The first time I rebooted I had forgotten the power cable on one of the disks in the RAID1 (mirror) and let it boot up. So I shut down and put the power back in.

So now when it boots up I go into the RAID admin interface (between the BIOS screen and the OS loading):

• it shows the RAID1 as in error the logical device has one disk and says the other is disconnected or missing
• the other physical disk shows up as a single disk

If I boot to the OS (Windows 7 32 bit) the data all seems to be there.

If I go into computer management it says my partition is on a disk and working OK. But the other disk is offline because:

"The disk is offline because it has a signature collision with another disk that is online"

So I am guessing because I STUPIDLY booted up with only one of the disks powered on, the other disk fell out of synch with the mirror and so now cannot rejoin the mirror.

How do I fix this? I want to get the RAID1 mirror working again. There does not appear to be any "Repair" option in the basic RAID admin tool which I get into during startup before the OS boots.

I have not made any explicit changes to the online one (but I guess the OS has probably written some admin data).

Firmware vs OS RAID (aka Windows 8 Disk Mirroring vs Intel Onboard)

So Windows 8 is out and I have a new motherboard. I wish to create a RAID 1 coupling between two HDDs -- for storage purposes only (my OS is on an SSD) -- but I don't know which is the best route to take.

My motherboard (Z77 chipset) comes with Intel Firmware RAID, but since I only wish to use my RAID for storage, I wondered if I might be better to use Windows 8 Disk Mirroring?

Can anyone advise which is better? Or perhaps the pros and cons of each, if that's too contentious? I just can't see the benefit of Firmware RAID over Windows Disk Mirroring.

You can see my current setup here, if that might change things(?):

Thanks!

Is RAID 1 on a home PC useful? [closed]

Is RAID 1 on a home PC useful?

How does RAID 1 determine whether a disk is corrupted?

I've built a RAID 1 array of 2 disks, A and B.

That means that every bit on A is equal to a bit on B. If one disk fails, I can safely retrieve my data from the other disk. But then I started wondering: How true is this?

Let's say a bit 1 on A reads 0, but 1 on B. How would the RAID controller be able to tell, which one is corrupted and which one is not? Is this based on what the so called "S.M.A.R.T." technology reports, and is that really worth anything, or would I be just as well of with a non-RAID solution?

I can see why this is not a problem on RAID 5, so I'm planning to upgrade.

Do newer Mobo's do RAID in a way that allows the disks to be viewed as a normal non-RAID HDD if transferred to another computer?

I built a new PC this weekend, and one of the joys I had was to transfer my RAID 1 array to the new system with a different mobo. The disks were not recognized at all, by either the mobo (no surprise) or Windows XP.

Now with the disks running on the new system, out of curiosity I switched the BIOS from "RAID" to "AHCI" and booted into Windows. Much to my surprise, Computer Management showed the two HDDs as separate drives partitioned into 279 GB and 84 MB, and both as being healthy NTFS formatted disks. Neither were assigned a letter or mounted, and I didn't mount them because I didn't want to screw anything up.

So my question is... is it possible that RAID 1 support on my new motherboard is formatting the primary partition on each HDD in a stock standard way, and storing any RAID specific data in the separate small partition? Can anyone say with any certainty?

Mobo hardware is an MSI 790GX-G65, which is an AMD SB750 RAID chipset.

PS: This matters to me because I was planning on upgrading to Windows 7 and switching to software RAID to avoid problems with loosing my data if my mobo fails and my backups are not completely up to date.

Is it possible to use software raid in Windows 7 on the boot partition?

I want to use RAID 1 on my workstation configuration at work, and I've been looking at using the build in mirror functionality in Windows 7. When you click on the add mirror option it presents you with the following warning.

I've done some Google searching and the consensus seems to be that you cannot boot from a dynamic volume, but some forum posts seem to indicate that people have tried this with success (e.g. here).

With Google searches producing contradictory information I thought I'd ask you guys for an authoritative answer. Can I use the inbuilt Windows 7 mirroring for my boot partition? Or as I suspect, will it make it unbootable due to it being converted to a dynamic disk?

Why does an Intel RST RAID 1 array write faster with write-back cache disabled?

I have two HDDs (5900 RPM) in RAID 1 (mirror). I know, I know, it's painfully slow. I'm currently in the process of replacing them with faster drives, hence this question while I'm testing things.

For some reason, disabling write-back caching in the Intel RST options gives me much faster write speeds, and vice versa. From what I know, I'd expect write speeds to decrease with write-back caching disabled. Is that correct? Is this just a bug in the monitoring program?

Caching enabled:

Caching disabled:

Intel RST system report:

System Report

System Information
OS name:  Microsoft Windows 7 Professional 
OS version:  6.1.7601 Service Pack 1 7601
System name:  (redacted)
System manufacturer:  MSI
System model:  MS-7673
Processor:  GenuineIntel Intel64 Family 6 Model 42 Stepping 7 3.401  GHz
BIOS:  BIOS Date: 08/01/12 15:53:14 Ver: 04.06.04, ALASKA - 1072009

Intel® Rapid Storage Technology
Kit installed:  10.5.0.1007
User interface version:  10.5.0.1007
Language:  English (Australia)
Intel RAID controller:  Intel(R) Desktop/Workstation/Server Express Chipset SATA RAID Controller
Number of SATA ports:  6
RAID option ROM version:  10.5.0.1034
Driver version:  10.5.0.1007
ISDI version:  10.5.0.1007

Device Information
Name:  Array_0000
Size:  3.6 TB
Available space:  0 GB
Disk data cache:  Enabled
Number of volumes:  1
Volume member:  OS
Number of disks:  2
Array disk:  5YD2V3WZ
Array disk:  5YD2VEPK

Name:  OS
Status:  Normal
Type:  RAID 1
Size:  1.8 TB
Data stripe size:  64 KB
Write-back cache:  Enabled
System volume:  Yes  
Initialized:  Yes  
Verification errors found:  72
Blocks with media errors:  0
Physical sector size:  512 Bytes
Logical sector size:  512 Bytes
Parent array:  Array_0000
Number of disks:  2
Array disk:  5YD2V3WZ
Array disk:  5YD2VEPK

Disk on port 0
Port location:  Internal
Status:  Normal
Type:  Hard disk
Usage:  Array disk
Size:  1.8 TB
Serial number:  5YD2V3WZ
Model:  ST2000DL003-9VT166
Firmware:  CC32
System disk:  No
Password protected:  No
Disk data cache:  Enabled
Native command queuing:  Yes  
SATA transfer rate:  6 Gb/s
Physical sector size:  512 Bytes
Logical sector size:  512 Bytes

Disk on port 1
Port location:  Internal
Status:  Normal
Type:  Hard disk
Usage:  Array disk
Size:  1.8 TB
Serial number:  5YD2VEPK
Model:  ST2000DL003-9VT166
Firmware:  CC32
System disk:  No
Password protected:  No
Disk data cache:  Enabled
Native command queuing:  Yes  
SATA transfer rate:  6 Gb/s
Physical sector size:  512 Bytes
Logical sector size:  512 Bytes

(redacted other disks)

Can RAID 1 have more than two drives?

Recently I had a discussion with a teacher of mine. He was claiming that you could set up RAID 1 with five drives and that the data would be mirrored over all of these drives.

I told him a RAID 1 with 5 drives wouldn't work like that. It would be a RAID 1 with two drives and would use the other three drives as hot spare.

He also said that RAID 6 is identical to RAID 5 but you can place all the parity checks on the same drive. I thought RAID 6 was a RAID 5-like solution where two drives where used for parity.

Who's right, then?

RAID 1 not performing as expected

I recently bought a new 320Gb hard drive for my computer to set up RAID 1 on it for some added security. Installation went as smooth as could possibly be (plug in power, plug in data cable, start up computer, Intel software recognized new drive, right click create RAID 1, done!).

However, for some inexplicable reason, I seem to have strange test results when using BENCH32. On my old configuration, a single 7200 rpm drive, I achieved about 60 MB/s write and 70 MB/s read. With a new RAID 1 configuration, I would expect the write to be slightly diminished but read to be significantly improved (though not exactly double speed). However, with the new configuration, I am getting 90 MB/s write and only about 80 MB/s read.

I should NOT be getting improved write performance, especially NOT better than read!

What's going on?

My system setup is:

q6600 2.4ghz CPU
4Gb DDR2 667mhz RAM
on board Intel ICH9R "RAID chip"
2x Seagate 7200 RPM 320GB drives in RAID 1
Widows 7 home premium 64-bit

Can I take my ReadyNAS drive in Raid1 and plug it straight into new different machine?

I would assume that I can just take my HDD out of my NAS (in raid1 mirror) and plug it into another enclosure and have it work off the bat but I'd like to make sure...

Any ideas?

Edit: My current setup is a Netgear ReadyNAS in (hardware) raid1. I'm hoping to replace this with a home theatre type PC (possibly running Ubuntu), and would like to migrate my data without having to do a bulk transfer over my network between the 2 machines.

Can anyone confirm the case for the Netgear ReadyNAS?

Edit:

Ok after further reading it seems that the ReadyNAS Duo formats my drive as ext3 in 16k blocks. There are instructions for mounting a drive into a linux box here: Mounting Sparc-based ReadyNAS Drives in x86-based Linux

There is also talk about a linux image here: ReadyNAS Data Recovery - VMware recovery tool

I'm not sure whether this means they ReadyNAS actually implements software raid under the hood, or what?

So it appears like it IS do-able, but do any of you linux guru's know whether this is viable and whether the fact that they are in raid 1 affect matters?