Hello everybody!
Watch this video to find out how to replace a dead controller without losing data.
How to import an external configuration, replace the controller with a different model, and
how to extract information from disks of a RAID system when the controller is missing.
In a modern IT environment, there could be several reasons why system administrators
would like to change from one RAID controller to another.
With the growing amounts of data to process, sooner or later its becomes necessary to expand
the disk array, but often you cannot do it because of the old controller, and sometimes
controllers may just fail.
Whatever happens, there is one question to answer: can you migrate to a new device without
losing data?
Yes, you can, and there are at least two methods of migration: the difficult one, which requires
you to make a backup copy of data, bring the disks to the new controller, reconfigure the
array and recover data from the backup; and the simple one, where you just connect
the drives to the new controller and import the external configuration.
The second option involves a certain risk of data loss but lets you save a lot of time
instead.
Unfortunately, the varying methods used to store RAID configuration data make it impossible
to transfer data between storage system of different manufacturers without data loss.
The RAID configuration data is stored on the drives that make up the array.
Usually, this information is located in the first or last sectors of each drive and is
known as metadata.
This metadata is written to the drives by the RAID controller’s firmware when the
array is created.
This configuration is duplicated on each of the drives, and all the service data is absolutely
identical, except the drive number.
That is why, when the drives are connected to a different controller, it should identify
the old configuration and import it without losing data or reconfiguring partitions or
arrays.
RAID controller manufacturers use different approaches to storing this information.
Let’s move on and find out how to select a proper replacement for your old controller.
How to replace a RAID controller without losing data
The first thing to remember is this: if you make changes to a RAID configuration or replace
the adapter (or expansion) card, there is always a risk of data loss.
To secure yourself against losing data from the RAID system, perform full backup and check
it before you start the migration process.
To replace a dead controller, it’s better to choose a device of the same model; if that
is not possible or your model is outdated, you can choose a controller of the same brand
but with a newer configuration.
There should be no difficulties in replacing an expansion card with a device of the same
model: the only thing you may have to do is to update its firmware.
When replacing an older model with a new generation device from the same manufacturer, visit its
official website to make sure if the new card supports the configuration used with the old
one.
The manufacturer’s website should contain a list of interchangeable and supported devices.
https://www.dell.com/learn/us/en/04/campaigns/dell-raid-controllers?c=us&l=en&s=bsd I have a RAID 5 system consisting of three
drives and based on a Dell controller, model PERC H310.
For illustration, I’ll show you how to replace it with another device of the same manufacturer,
model H710.
There are several possible scenarios of how the storage system may behave after installation
of the new controller.
The first case is that the device imports the disk array automatically.
When booting, the system will display the notification that a foreign configuration
is found, and that you need to press a certain key to import it; in my case, that key is
F. After that, the controller will automatically identify and load the previous configuration,
and when the operating system has booted, you will find all the data just where it used
to be.
In the second scenario, you’re going to see a notification saying that the system
found a foreign configuration, but it failed to load it automatically, and you can configure
it by opening the controller BIOS.
Do it by pressing the key shortcut displayed on the screen (С key or Ctrl+R).
In the window that opens, select the upper line and press F2 for configuration, select
“Foreign Config” and press “Enter,” and in the submenu that opens select “Import”
to import an external configuration, or “Clear” to remove it.
Of course, we select “Import.”
It may take a few minutes before the configuration is processed, and after that the utility should
display a list of virtual drives that used to be configured for this system.
This is the end of the controller replacement procedure, and after you boot the operating
system you can make sure that no information is lost, and all files are still where they
should be.
Here’s an important piece of advice.
When connecting the drives to the new controller, make sure you connect them in the proper order.
Yes, some controllers can import the configuration regardless of the order in which the disks
are connected, but many don’t, so it is recommended to connect them in the same way
they were connected to the old controller.
If they were connected to the zero port of the old controller, with the new controller
they should be connected to the same port, otherwise an attempt to import will end in
failure and data will be lost.
Also, you may have to change the controller firmware to the version used with the old
controller, or update the firmware.
How to replace your RAID controller with a similar model from a different manufacturer
As I said earlier in this video, RAID controller manufacturers use different approaches to
storing service information on the drives.
So if you plan to replace the dead controller with a different model from another manufacturer,
there are a few things to keep in mind.
You need to know if new controller supports the general format of drive data (DDF), which
DDF version it supports, and what order is used to write bytes and store information
in the disk array.
DDF (Disk Data Format) is the structure of formatting data in drive groups within a RAID
system.
It provides a basic level of interaction between various RAID vendors.
The general DDF structure in RAID is very important because it ensures data migration
between storage systems from different manufacturers without losing data.
At the moment, it is available in two versions - 1.2 and 2.0.
Various controller models and brands may support the first version, the second version, or
both, so this is an important thing to find out when looking for a replacement.
Another feature to pay attention to is the order or sequence of writing bytes.
In computing, all information is represented in sequences of bytes.
If a certain figure cannot be represented as one byte, it really matters in which order
bytes will be written to the computer’s memory.
With the exception of mixed and inverted orders, there are two main ways to write bytes, Big
Endian and Little Endian.
The first one (Big Endian) will write bytes left to right (it looks like this: the figure
123 is written as 1,2,3).
The second order (Little Endian) will write bytes in an inverse order, and the same figure
123 will be written as 3,2,1.
You can see it in detail with the help of a Hex editor.
If the controller used to build a RAID system and write its data works with the first order
of writing bytes, and then you replace it with a controller using the second order,
you may have difficulties with importing the configuration.
The import operation will either fail or the controller will be unable to identify the
foreign configuration.
In the course of testing, we managed to import an external configuration with the following
Dell PERC controller models: H310, H330, H710, H830, so these devices can be replaced without
risking loss of data.
With RAID 5 based on Dell PERC H310, we managed to import the external configuration without
loss of data to various models of the same manufacturer.
As to third-party vendors, a controller Fujitsu D311 with LSI firmware detected the external
configuration on the drives and suggested to import it during the first boot.
After that, we opened the controller’s BIOS and saw that the previous configuration has
not changed, and after the operating system booted, all the files in the disk array remained
intact.
However, in the case with a similar controller on LSI firmware, IBM ServeRAID M5016, we failed
to import the external configuration, because the controller could not identify the configuration
properly.
When we tried to import a configuration from the controller Dell PERC H310 to the controller
Adaptec ASR 6805T, the second controller encountered an error, and importing the configuration
without losing data is impossible.
If we compare their features, we can see that the Adaptec device supports DF version 2.0
and has a different write order for bytes, which is most likely the main reason of failure
to import the configuration.
Controllers produced by HP have their own structure of building RAID systems and writing
data to the drives in the array.
That is why there are little chances of success if you try to replace an HP controller with
a controller of a different brand.
If the disk array is a bootable one, and you replaced its controller with a different model,
you may have to install an operating system driver for the new device, otherwise the whole
system may refuse to boot.
Also, you should take into account that not all RAID levels can be migrated to a different
controller model; this applies to multilevel arrays like RAID 10, 50, 60 which include
several groups of disks.
If you are trying to import an external configuration and encounter an error, this could be caused
by your RAID being a multilevel one.
How to recover data if the controller is dead If you failed to find a replacement for a
dead controller, but you still want to extract some important data from the drives, use a
specialized tool to recover data from RAID systems.
Hetman RAID Recovery can restore data from disks of a RAID system even if the controller
is missing.
The utility reads from the storage system all the information about the controller,
the motherboard, or the software used to create a disk array, and then rebuilds the damaged
RAID.
After that, you’ll be able to scan it and recover the critically needed information.
Conclusion The Drive Roaming feature or options to import
an external configuration can be found in almost all modern controllers.
That is why we may suppose that replacing one controller model with the other model
by the same manufacturer should not cause any problems.
If the device in question is pretty old, you should first check its compatibility by visiting
the manufacturer’s official webpage.
However, the best method be to transfer the information with the help of a backup copy
- in that case, the successful result is guaranteed.
That is all for now!
Hopefully, this video was useful.
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Thank you for watching.
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