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mdadm assembles AVAGO/LSI MegaRAID controller RAID 5 array

It is possible to read data with the software Linux raid using mdadm tool from a RAID 5 array created with the hardware raid controller AVAGO MegaRAID 9361-4i (LSI SAS3108).

Here, how a RAID 5 array with 3 hard drives and 1 SSD ( with CacheCade in write-through mode) is assembled by the mdadm and Linux software raid:

livecd ~ # cat /proc/mdstat 
Personalities : [raid0] [raid6] [raid5] [raid4] 
md125 : active raid0 sda[0]
      937164800 blocks super external:/md127/1 1024k chunks
      
md126 : active raid5 sdb[2] sdc[1] sdd[0]
      23436722176 blocks super external:/md127/0 level 5, 1024k chunk, algorithm 2 [3/3] [UUU]
      [==============>......]  resync = 72.0% (8438937704/11718361088) finish=336.8min speed=162234K/sec
      
md127 : inactive sdb[3](S) sda[2](S) sdd[1](S) sdc[0](S)
      2100568 blocks super external:ddf
       
unused devices: <none>

Note, it is essential that the CacheCade device is in write-through mode, which means the cache device is used only for reading and the data on the RAID array is consistent and written on it. The RAID 5 array was created here – AVAGO MegaRAID SAS-9361-4i with CacheCade – create a new virtual drive RAID5 with SSD caching. It seams possible for the data to be consistent if the CacheCade is write-back mode if there were few small writes and orderly shutdown prior to the removal of the AVAGO MegaRAID 9361-4i.
So, the above devices use proprietary LSI format, but here Linux software raid supports some of them:

md125 – the SSD device, which is a read cache only.
md126 – 3 hard drives in RAID 5 array.
md127 – logical device, which provides transparent interface to the

The important device is md126 and can be mounted under some live Linux CD/USB. Further, the md125 is a device, which has GPT partition table with 5 partitions:

livecd ~ # parted /dev/md126 --script print
Model: Linux Software RAID Array (md)
Disk /dev/md126: 24.0TB
Sector size (logical/physical): 512B/4096B
Partition Table: gpt
Disk Flags: 

Number  Start   End     Size    File system     Name                  Flags
 1      1049kB  211MB   210MB   fat16           EFI System Partition  boot, esp
 2      211MB   1285MB  1074MB  ext4                                  msftdata
 3      1285MB  23.9TB  23.9TB  ext4                                  msftdata
 4      23.9TB  24.0TB  53.7GB  ext4                                  msftdata
 5      24.0TB  24.0TB  16.8GB  linux-swap(v1)                        swap

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Add cachecade SSD to an existing virtual drive in AVAGO MegaRAID with storcli64

Increase the IO performance of big storage consisting of hard drives with the CacheCade feature with MegaRAID hardware controllers. Here are the commands to ensure adding an SSD to cache storage of hard drives and the whole output:

storcli64 /c0 add VD cachecade r0 drives=252:0 WB
storcli64 /c0/v0 set ssdcaching=on

Summary and explanation

The controller used is AVAGO MegaRAID SAS9361-4i
Three 12T hard drives and 1 SSD 1T.
RAID5 of 3 hard drive. The name of the virtual drive is v0.
The CacheCade is in RAID0. The name of the virtual drive is v1.
The CacheCade is in WriteBack mode. The WriteBack mode is dangerous when the CacheCade device is RAID0, because there is no redundancy, but it’s OK if the purpose of the machine is just a proxy cache. WriteBack mode leads to much more performance to gain from the cache device over slow device sotrage, but should be carefully planned when using RAID0 cache (or single) device.
Using storcli – the cli command line tool to manage a (LSI) MegaRAID.
Add CacheCade RAID0 device by the first command. It will create a virtual drive RAID0 with the name v1.
Ensure the caching is enabled for the virtual device it should be by explicitly setting it with the second command. Adding only a CacheCade device may not add the cache virtual device to the existing virtual devices!

Output of a real world example

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AVAGO MegaRAID SAS-9361-4i with CacheCade – create a new virtual drive RAID5 with SSD caching

Here is howto article for creating a RAID5 device in MegaRAID SAS-9361-4i with SSD caching. First and really important thing is to have the CacheCade ability to the controller, which should be purchased because it is a software add-on.
To have an SSD caching your virtual raid drive (probably hard disk drives) with a MegaRAID controller one setup is the following:

And it is advisable to have Cache Protection to protect your setup (it is extra protection to the battery kit – it is not the same) – LSI LSI00418 LSICVM02.

You can check also our AVAGO MegaRaid SAS 9361-4i with CacheCade and CacheVault BIOS configuration utilities review.

Here are the steps to create a RAID5 device with SSD caching using the BIOS Configuration Utility:

STEP 1) Supermicro device initialization

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AVAGO MegaRaid SAS 9361-4i with CacheCade and CacheVault BIOS configuration utilities review

Here is the screenshots’ review of LSI LSI00415 MegaRAID 9361-4i SGL controller with CacheVault Accessory kit LSI LSI00293. The controller has 3 hard disk and an SSD for the cache vault.
As you can see we use LSI, but in deed this is the AVAGO controller. First it was LSI, which was acquired by AVAGO and then AVAGO acquired Broadcom and rebranded to Broadcom. It is good to know it how these names are connected, because any controllers still use them in BIOS, management console cli, manuals and so on. You are going to see that in the controller’s BIOS and controller initialization boot up you can read only AVAGO – no LSI or Broadcom. Probably the most famous and familiar name of the three company names is LSI (hardware controller).
The screenshots are from the BIOS of “LSI LSI00415 MegaRAID 9361-4i SGL” with LSI LSI00293, CacheCade and LSI LSI00418 LSICVM02 – CacheVault Accessory kit.

So as you see you need two additional features to have a SSD as a cache device in your LSI (AVAGO/Broadcom) controller!

Check out our article AVAGO MegaRAID SAS-9361-4i with CacheCade – create a new virtual drive RAID5 with SSD caching.

SCREENSHOT 1) Booting the controller and checking the devices.

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