Question: Legacy readynas RAID implementation

[Sebazzz]

My ReadyNAS NVX Pioneer (x86, RAIDiator 4) is a bit old and in order to investigate the possibility to migrate the harddisks into a more modern system I'm investigating the way RAID is implemented.

From a functional perspective, I have 4 harddisks and my RAID configured as RAID 5.

I have already found out that RAIDiator appears to use standard Linux software raid, via mdadm.

Using mdstat I found out that the NAS actually has three RAID arrays!

ReadyNAS:~# cat /proc/mdstat
Personalities : [raid0] [raid1] [raid10] [raid6] [raid5] [raid4]
md2 : active raid5 sdd3[0] sda3[3] sdb3[2] sdc3[1]
      5846379888 blocks super 1.2 level 5, 16k chunk, algorithm 2 [4/4] [UUUU]

md1 : active raid6 sdd2[0] sda2[3] sdb2[2] sdc2[1]
      1048544 blocks super 1.2 level 6, 16k chunk, algorithm 2 [4/4] [UUUU]

md0 : active raid1 sdd1[0] sda1[3] sdb1[2] sdc1[1]
      4194292 blocks super 1.2 [4/4] [UUUU]

unused devices: <none>

md2 appears to be the actual RAID 5 array. The other arrays are a mistery to me. According to mounttab md0 appears to be the firmware, this appears not to be stored on a seperate flash chip? As for md1, this appears to be RAID 6 which is odd given I have only four hard disks.

So, how is RAID implemented on RAIDiator? Are md0 and md1 pseudo raid arrays?

[StephenB]

md0 is for your OS partition (which is mirrored using RAID-1 across all disks, so the NAS can boot from any disk).  Your guess that the OS isn't run from the flash is correct.  It's installed onto the disks at setup.

md1 is the swap partition.  Note RAID-6 can run on 4 disks with no problem.  You can confirm with swapon -s

md2 is your data volume.

If your disks were (or at some point had been) different sizes you'd see more.  My pro-6 once had a mix of 1.5 TB and 3 TB, and I have an md2 and an md3.   My data volume spans both (seamlessly).

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@Sebazzz wrote:

My ReadyNAS NVX Pioneer (x86, RAIDiator 4) is a bit old and in order to investigate the possibility to migrate the harddisks into a more modern system I'm investigating the way RAID is implemented.

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Note an OS-6 x86 NAS can be used for migration.  http://kb.netgear.com/29957/ReadyNAS-Migrating-disks-from-RAIDiator-4-2-to-ReadyNAS-OS-6-x86?cid=wmt...

[Sebazzz]

Thanks for the reply! That clears up a lot.

I don't seem to be able to find any explicit RAID configuration (not in the md configuration file at least). Are all drives auto-detected on boot? How does mounting /c from /dev/c/c work, since one would expect the mount to happen from /dev/md2.

[StephenB]

I've never researched how it boots, but mdadm scans the partitions and assembles the arrays.

[mdgm-ntgr]

After starting the RAID you then use some commands from lvm2 to scan for volume groups, activate the volume group and then you can mount the volume.

# vgscan
# vgchange -a y

# mkdir /c

# mount /dev/c/c /c

When done

# cd

# sync

# umount /c

# vgchange -a n

# mdadm --stop --scan

If your current system is still working I'd recommend getting a new OS6 NAS with new disks and using backup jobs to copy the data across.