RAID rebuild times.

ajf

ajf

ajf

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This more out of interest than anything.
We purchased a new Dell server that should have had a single 48Tb RAID 5 array.
They managed to screw it up and created two separate arrays so we had to rebuild it.
Currently looking at around 9 days(!).

Question then, how do Dell commercially configure these large RAID arrays when building servers?
I can't see them having a room of servers all merrily building away for 9+ days at a time.

On another note, any ideas if we could speed up the rebuild?
 
Surely that rebuild time is only if you want to maintain your data. If you want to create a spanking new RAID 5 array it should be near enough instant.

If you have some form of drive integrity check being performed though it will take ages.
 
Maybe that is the case then.
I am not personally doing it. The drives are new and blank so no data to keep anyway.
 
the array will be created instantly but RAID 5 array have to do that time consuming striping build thing (sorry cant remember what its called) which takes ages.

It will be quicker if you are not retaining data as its not moving it about but it just takes time. Make sure your cache settings are on full write when you rebuild for speed.
 
Whatever it is doing, it should do it in the background. You should be able to have full access to the array straight away.
 
"RAID 5 is no longer recommended for any business critical information on any drive type. RAID 50 is no longer recommended for business critical information on Class 2 7200 RPM drives of 1TB and higher capacity." - Dell in 2012.

I'm honestly surprised they shipped a RAID5 array that big, it's almost guaranteed to have issues. As long as it's just a temp store it should be fine.
 
What size are the drives and how many?

48TB on RAID5 however is a bit nuts? The parity calculations for that must be astronomical.
 
How are you rebuilding it? Through software on the OS or via the controller program at boot? I found via the controller program was a lot quicker!
 
Think we found the 'problem'.
Looks like instead of trashing both arrays and starting from scratch, only one was trashed and the disks added to the other one, hence it was doing a full rebuild rather than just an initial build.
We chose RAID 5 as it was deemed sufficient for the use. It isn't live data, but is used for Veeam backups of our VMs, hence the requirement for the large size.
It's 12x 4Tb SAS disks on a hardware RAID controller. Server is a Poweredge 730XD.
The rebuild was via the Dell Open Manage software as it was done remotely.
 
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