Transfer array from Pegasus32 R6 to R4 when R6 is suddenly failing

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Ignace Roelens posted this 3 days ago

Hi,

I'm currently having the Pegasus32 R4, but I'm thinking to add an R6 to the setup.

Questions:

- I would like to use the R6 as the main RAID, where one disk array of 4 disks is having both RAID 5 and RAID 6 logical drives. Having 1 pass through drive as a backup disk for the Mac, having 1 spare drive for migrations or as a hot spare. Now my question, if one day the R6 would fail, would it be possible to swap out the 4-disk array and plug them inside the R4, hoping to keep the RAID 5 and RAID 6 fully operational again and this immediately? I know that this is normally possible using the transport feature, but I'm not sure if the transport is not planned due to a failure if this would work, especially considering two different Pegasus32's? Are there any restrictions or preconditions to make this work? Like having to use the upper or lower 4 trays? Related to this, maybe a technical question, where does the Pegasys32 gets its configuration from, is that stored on the disks too?

- In that setup I would connect the R6 directly to the Mac, and the R4 connected to the R6. I would use the R4 as an additional offline backup. Question, can I keep the R4 unpowered all the time, so the 230V unplugged from the mains, but keeping the Thunderbolt cable connected to the R6? Will that do any harm to the Thunderbolt ingterfaces electrically, since power is on those cables for for example charging? It's because I've tried using the software power down feature of the R4, but the R4 seems not to remember its power state when the main is completely removed? So the only way is to cut the mains myself, but then I'm wondering if this is healthy in a prolonged way for the Thunderbolt interfaces?

- Last simple question, I'm assuming that a disk drive in pass through, if one day is put into any other enclosure, would still look the same to my Mac? So a pass through drive is 100% transparent?

Trying to make/define a fail save system...

Thanks in advance!

Kind regards,

Ignace.

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R P posted this 2 days ago

Hi Ignace,

Now my question, if one day the R6 would fail, would it be possible to swap out the 4-disk array and plug them inside the R4, hoping to keep the RAID 5 and RAID 6 fully operational again and this immediately?

Yes.

It's simple to do, make sure both Pegasus units are powered off, unplugging the power cable is best, then swap the drives to the corresponding slots on the R4. After you connect the power and Thunderbolt and let the R4 boot the volume should mount.

Related to this, maybe a technical question, where does the Pegasys32 gets its configuration from, is that stored on the disks too?

Yes, all the RAID metadata is stored on the disks.

Question, can I keep the R4 unpowered all the time, so the 230V unplugged from the mains, but keeping the Thunderbolt cable connected to the R6? Will that do any harm to the Thunderbolt ingterfaces electrically

This should be OK.

Ignace Roelens posted this 2 days ago

Hi Richard,

Thanks for the responses!

swap the drives to the corresponding slots on the R4

So this probably means the top 4 slots on the R6?

So a pass through drive is 100% transparent?

Do you have an answer for this one above?

Oh, maybe a stupid question, but I don't find a clear answer; is it always better to shutdown the Pegasus for removing (or adding) disks, even if they are in failure mode or when we need to do a rebuild? Since I have no idea how SATA disks can and/or may be really hot swapped, or if it does depend on the HDD type itself too?

Thanks.

Kind regards,

Ignace.

R P posted this yesterday

Hi Ignace,

So this probably means the top 4 slots on the R6?

These were the drives you mentioned for creating the RAID5, so yes. The important thing is to keep them in the same order.

- Last simple question, I'm assuming that a disk drive in pass through, if one day is put into any other enclosure, would still look the same to my Mac? So a pass through drive is 100% transparent?

Yes.

In fact, if you placed the disk in a USB dock, the volume should mount. I put one drive of a RAID1 set in a USB dock and it mounted and I was able to access the data and write files.

A passthru disk is simply made visible to the operating system, you use disk utility to put a filesystem on it. A passthru disk is not part of a RAID set, it's just a raw drive to the OS.

Ignace Roelens posted this yesterday

Hi Richard,

Ok, this sounds all great.

Thanks for the information provided!

PS: Surprised though that even a RAID1 can mount! Ok, it's mirrored and contains all data, but then the metadata stored by the Pegasus should be on an area that doesn't conflict with the file system, somewhere in the front or a gap in the front, I would need to have a look into how partitions and file systems are organized binary.

Kind regards,

Ignace.

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