Pegasus R6 Raid 6 or 5

  • Last Post 08 November 2021
Alexander Snelling posted this 01 November 2021

Morning. Afrer recently losing a load of data after an array went down (thankfully almost all of it can be recreated) - I've purchased another (fourth) Pegasus for extra backup. My thinking is to make this a large, less used but fool proof back up and as such I thought Raid 6 would be a good option (using 6x 2TB drives) however I am not sure if this is actually recommended for video and if so what settings (stripe/sector size) I should use.

The Wizard seems o suggest I should be using Raid 5 but I am a bit skeptical after having had my fingers burned once - would Raid 6 be safer and is it recommended?

I'm on a Mac with OS11 probably soon to be OS12


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Alexander Snelling posted this 08 November 2021

Hi RP, Tried three different TB cables but yet it could well be a power supply issue. Would have thought the PU app might have  flagged that up but maybe not. Might have to get my screwdriver out...

 The weird thing is thought that it just won't mount. DU can see it correctly but it just won't mount or appear on the desktop

R P posted this 08 November 2021

Hi Alexander,

Connection issues are often caused by a bad/intermittant TB cable. I've been using the same TB2 cable for over a year with no issues and constant insertions. But many cables are a lot older, so if a second cable is available it can be used for debug.

The only other root cause would be some sort of hardware problem. Some Pegasus 1 units are seeing power supply issues.

Alexander Snelling posted this 08 November 2021

Hi there. I am struggling with this last step. Seems to me my Pegasus has some sort of connection problem.

When first connecting - phydrv, array and even logdrv seem all OK but then somehting seems to not happen and it will not mount. Have tried this on two computers with different operating systems and different thunderbolt cables. Still no dice. Seems like something possible hardware realted is preventing this from mounting or am I missing a key stage. The only thing I havent seen happening is the initialisation/formatting of the LogDrv which I thought would take 20 hours odd.

Service report attached.




R P posted this 01 November 2021

Hi Alexander,

RAID6 is slightly slower than RAID5 as it needs to generate and write an extra parity stripe, but this should not be a concern if the volume is used for backup.

There are many forums where posters for various reasons say that with today's larger drives RAID5 should not be used. In practice, this is rarely a problem, and if the enclosure is 4-drive then you're usable space is greatly reduced and RAID5 is preferred.

Some use RAID10, but if the wrong two drives fail then the storage will be offline, with RAID6 any 2 drives can fail and the storage will remain online, so RAID6 is more robust.

The wizard is designed for quick and easy setup for the most common configuration, but if you want something different Promise Utility and the CLI will easily handle the task.

The steps are simple, but there are more of them.

1. Create an array of the drives you want to use (probably all of them)

2. Create a RAID6 logical drive in the array.

3. From diskutil, use the ERASE function to put an HFS+ journaled filesystem on the LUN.

The drive should then appear on the desktop. If you did not name the drive with diskutil it's easy to rename it afterwards.