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