Previously, we created a RAID 5 volume with 3 hard disks (2 used for data storage and the 3rd for parity of the RAID volume).
However, in the event of a hard drive failure, you would necessarily have to buy a new hard drive and open up your computer / server to physically replace it at the time the failure occurs.
It takes time and it's not possible in production.
To reduce the downtime of your services, you can add an additional hard disk that you define as "Hot Spare".
This can then be used as a spare hard drive in the event of a failure of a physical drive in your array or in any array of your Microsemi Adaptec SmartRAID controller.
This behavior will depend on the choice made when adding this physical disk as a "Hot Spare".
Hot Spares can be of the "Dedicated" or "Auto-Replace" type.
In the case of this tutorial, we will configure it as "Dedicated Spare", which means that :
Hot Spares limitations :
- PDF : Microsemi Smart Storage Controllers - User Guide - maxView Storage Manager
- for the Spares : "6.1. Dedicated Spare or Auto-Replace Spare ?" at page 40
- for redundant or not redundant RAID : "F.2 Non-redundant Logical Drives (RAID 0)" at page 165
For this tutorial, we plugged in a new SAS hard drive with cable 3 which is already connected to our Microsemi Adaptec SmartRAID controller on the CN4 port.
The 3 SAS hard drives plugged in below are those of our RAID 5 volume and are plugged in with cables : 0, 1 and 2.
Note that in our case, this new SAS hard drive is identical to the others. It therefore has the same interface (SAS) and the same capacity (size).
This can therefore be used to protect our RAID 5 array without any problem.
When starting your computer / server, press the "CTRL + A" (QWERTY keyboard) or "CTRL + Q" (AZERTY keyboard) keys.
Info : if you can't restart your server, access the "maxView" web interface and go to the next step of the tutorial.
In the Microsemi Adaptec configuration tool, go to : Configure Controller Settings.
Then, in : Modify Controller Settings.
As you can see, by default the "Spare Activation Mode" option is set to : Failure SA.
If you try to change the value, you can choose between :
Important : as indicated by Microsemi, if you want to protect a RAID 0 with Hot Spare, you are obliged to configure this activation mode on "Predictive SA".
Indeed, when a physical disk in a RAID 0 fails, this immediately causes a permanent and total loss of data of everything that was on the array in RAID 0.
RAID 0 is therefore strongly discouraged under normal circumstances, unless you really know what you are doing.
In our case, we will choose "Failure SA" since we are using RAID 5.
If you already have a free hard drive and can't restart your computer / server, install maxView on it (if you haven't already) and access this web interface.
Then, select your Microsemi Adaptec SmartRAID controller on the left and you will see that an additional Physical Device has appeared and it is not assigned (Unassigned Drive) at the moment.
If you go to the "Resources" tab of your controller, you will see that the status of your new physical drive is "Ready".
Which means you can use it later as a Spare if you want. Click on the little blue arrow to its right.
As you can see, this physical disk is in "Ready" state and its Configuration Type is "Unassigned".
Which means your controller is not using it at the moment. This physical disk is therefore free.
To configure the activation mode of your future Spares, select your controller on the left and click on the 1st icon of the "Controller" block located at the top of the page.
In the "Data Protection" tab, you will find the same "Spare Activation Mode" parameter with the values :
As a reminder : if you want to protect a RAID 0 with a Spare, you must choose "Predictive" to try to protect your RAID 0 array.
Warning : it's quite possible that a physical disk in your RAID 0 fails too quickly and that the reconstruction does't have time to be fully carried out.
This is not necessary, but if you can restart your computer / server, be aware that you will be able to check whether your physical disk is free or not by accessing the Microsemi Adaptec Configuration Tool (ACU).
In this configuration tool, go to : Disk Utilities.
In the list that appears, we find our new hard drive connected to the "CN4:01:003" location.
Select it and press Enter.
Select "Device Information" and press Enter.
At the bottom, you will see that this physical disk is not associated with an array (Associated to Array : No).
Which means that this physical disk is free and that you can define it as Spare if you wish.
If you can't restart your computer / server, you can also check it very easily via maxView Storage Manager.
Select the physical disk you just plugged in and you will see that its status is "Ready". Which means this one is free.
Still in the configuration tool accessible when starting your computer / server, go to : Array Configuration.
Then, in : Manage Arrays.
Select the array you want to protect with a Spare and press the "CTRL + S" keys (as shown at the bottom of the screen).
If no physical disk eligible for this array was found by your Microsemi Adaptec SmartRAID controller, the "No eligible disk found to create a hot spare" error message will appear.
If this is the case, refer to the limitations listed in step "1. Information about the Hot Spares system" of the tutorial.
In particular, make sure that the physical disk you want to use :
If your physical disk is eligible, this screen will be displayed with 2 columns :
To add a physical disk as a Spare, use the arrow keys to select a physical disk, then press the space bar or the "Insert or Ins" key to add it to the "Selected Drives" list.
Once you have selected the disk(s) you want to use as a Spare for this array, press Enter to confirm the selection.
Confirm the changes by pressing the "Y" letter.
Select the type of Spare you want to use :
In the case of this tutorial, we have selected "Dedicated Spare Drive".
Then, press Enter to finish configuring the Spares.
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