topic RAID size for adding 56 133Gb FC Disks in ONTAP Discussions

RAID size for adding 56 133Gb FC Disks

SETH_DICKERSON — Thu, 05 Jun 2025 06:42:04 GMT

Hi,

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.

Seth

RAID size for adding 56 133Gb FC Disks

scottgelb — Wed, 02 Nov 2011 18:10:39 GMT

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

SETH_DICKERSON — Wed, 02 Nov 2011 18:18:08 GMT

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?

Thanks,

Seth

Re: RAID size for adding 56 133Gb FC Disks

scottgelb — Wed, 02 Nov 2011 18:19:46 GMT

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