Data ONTAP Discussions

RAID size for adding 56 133Gb FC Disks


I am needing some help with figuring out what the optimal RAID size would be for adding 56 133Gb FC disks to my current system. I am using an FAS3040 with Data OnTap vs. 7.3.4.  I will be configuring for RAID DP and would like to only allot 4 disks for parity out of the 56 total disks.  All help is greatly appreciated.



RAID size for adding 56 133Gb FC Disks

With 32-bit aggregates, you can have 141 total disks (data+parity) and a max of 123 data disks with 144GB drives.  With 56 disks, I would consider 2 spares with 54 disks and go with 3 raid groups of 18   [3*(16D+2P)]... that keeps raid groups the same size for better performance and meets the requirements for rapid raid recovery with 2 spares which is plenty for 56 drives as long as you have a support contract or extra disks to swap out when they fail.

If you want only 2 raid groups (4 parity drives) you could go with 2 raid groups of 27 [2*(25D+2P)] but I wouldn't go with raid groups that big (the max is 28 with RAID_DP but odds of failure, rebuild time, etc. not a great idea to go that big).

RAID size for adding 56 133Gb FC Disks

Thanks Scott!

My only issue is that these disks went out of warranty earlier this year.  My boss wants me to continue to use them but make sure I have up to date Full and Incremental backups of the data in the event of loss.  Which is why I was thinking of having 4 parity disks.  Knowing now that  there is no warranty would you still think 3 raid groups of 18 is fine?



Re: RAID size for adding 56 133Gb FC Disks

3 RAID groups is safer than 2 especially without warranty.. I would source pre-owned disks to keep shelf spares too.