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RAID 6 - LFF - Not enough free disk space?
https://3parug.net/viewtopic.php?f=18&t=476		 Page 1 of 1
Author:  rjbaran17 [ Wed Nov 13, 2013 7:45 pm ]
Post subject:  RAID 6 - LFF - Not enough free disk space?
Hello,

We have a new 3PAR 7200 with an additional Large Form Factor drive chassis. There are (8) 3TB 7200K Near Line LFF drives in the LFF chassis. There are no SFF drives. The system will not let us create a RAID 6, claiming there is not enough available free space? Why would this be?

Is it also true that we can't create a RAID 5 with NL drives? When we try and create a RAID 5 across the NL drives, it states the drive configuration is not supported?
Author:  Josh26 [ Wed Nov 13, 2013 11:56 pm ]
Post subject:  Re: RAID 6 - LFF - Not enough free disk space?
Check your availability level. It defaults to "cage", and you probably don't have enough cages to do RAID 6. Changing to "mag" should resolve it.
Author:  giladzzz [ Thu Nov 14, 2013 3:12 am ]
Post subject:  Re: RAID 6 - LFF - Not enough free disk space?
Hi
change availability from cage to magazine also there are hardware restrictions on raid configuration
as for raid 5 it's disabled by default for NL drives but it is a system parameter
in CLI write "setsys AllowR5OnNLDrives yes"
Regards
Author:  hdtvguy [ Thu Nov 14, 2013 6:38 am ]
Post subject:  Re: RAID 6 - LFF - Not enough free disk space?
I did not realize the concept of "Magazine" existed in the 7000 series as the drives all plug into the back-plane and the desired HA would be cage if you have enough trays to allow for a tray failure.
Author:  yizhar [ Thu Nov 14, 2013 3:41 pm ]
Post subject:  Re: RAID 6 - LFF - Not enough free disk space?
Hi.

The 3PAR 7200 has 2 controllers.
Each of them handles half of the disks during normal operation (the other can take over).

So - each controller is managing 4 disks out of 8, therefor you cannot create RAID6 in such configuration (which actually means RAID60) .

I was hit by similar problem, as I have a 7200 with 12 NL disks in the second cage,
which means 6 NL disks per controller.
I can create RAID 6 , however I am limited to 4+2 set size which means 33% disk space penalty,
and I cannot use something reasonable like 6+2 or 8+2 set size.
So I opted to not use RAID6 at all on those disks.

Your options are:

* Create RAID1 (RAID10) volumes for production data.

* Create RAID5 (RAID50) CPG and volumes only for non production data, such as snapshots,
backup or archives files.
For this you need to enable "AllowR5OnNLDrives" as mentioned by giladzzz above.

* Or - purchase more NL disks.

Yizhar
Author:  Josh26 [ Thu Nov 14, 2013 5:17 pm ]
Post subject:  Re: RAID 6 - LFF - Not enough free disk space?
kluken wrote:
I did not realize the concept of "Magazine" existed in the 7000 series as the drives all plug into the back-plane and the desired HA would be cage if you have enough trays to allow for a tray failure.


Someone who doesn't have enough trays to do "cage", I can tell you I've configured our 7200 with "magazine". Because it doesn't actually have magazines, it's effectively just a case of a GUI using standardised terminology across the 3PAR range, and in this case it can be thought of as single disk magazines.
Author:  Richard Siemers [ Fri Nov 15, 2013 1:27 pm ]
Post subject:  Re: RAID 6 - LFF - Not enough free disk space?
Its a vocabulary problem... technically, a hot plug drive is a magazine of 1. ;)
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