ONTAP Hardware

Raid Group in mixed disks


I have FAS2040 and want to assign disks to an aggregate. Can someone recomen me good raid size.

I have a SAS disk shelf with 2 4*600GB  disks and 7 spare SATA(2.2TB) disks from another shelf .

I am not worried about the performance because I am going to use this to migrate the data to this new aggregate temporarily to rebuild the original aggregate, need max capacity.



Let me know the Ontap version and below mentioned points.

1.) What size are you looking for ?

2.) what kind of protection level RAID-DP or RAID-4 ?

3.) Want spare disks ?

I am looking for 15TB space.the rest are optional.

Your requirement of 15TB would require to mix SAS and SATA. Below mentioned are the rules to mix disks in Aggregate.

Rules for mixing disk types in aggregates

You can mix disks from different loops or stacks within the same aggregate. Depending on the value of the raid.disktype.enable option, you might be able to mix certain types of disks within the same aggregate.

The following table shows what types of disks can be mixed within an aggregate when the raid.disktype.enable option is set to off

SAS disks in SAS disk shelves SATA disks in SAS disk shelves FC disks in DS14mk2 FC or DS14mk4 FC disk shelves ATA disks in DS14mk2 FC or DS14mk4 FC disk shelves SSDs
Internal SAS disks Y N Y N N
Internal SATA disks N Y N Y N
SAS disks in SAS disk shelves Y N Y* N N
SATA disks in SAS disk shelves N Y N Y* N
FC disks in DS14mk2 FC or DS14mk4 FC disk shelves Y* N Y N N
ATA disks in DS14mk2 FC or DS14mk4 FC disk shelves N Y* N Y N

*Data ONTAP does not prevent these combinations. However, due to the large difference in performance between the two disk types, you should avoid these combinations.

BSAS disks are considered to be the same as SATA disks in this table.

SAS and SATA disks are not allowed in the same aggregate.

If the raid.disktype.enable option is set to on, all aggregates must contain disks of a single type. 

Note: If you set the raid.disktype.enable option to on for a system that already contains aggregates with disks of mixed type, those mixed aggregates continue to function normally and accept both types of disks. However, no other aggregates will accept mixed disk types as long as the raid.disktype.enable option is set to on.
Hope this will help

look like I can not mix SATA and SAS in teh same aggregate , this case I have to go for two aggregate.

What does make maximum space big raid size or small raid size?


Yes you are right. As you have 24 SAS disks and you need this space temporary. you can customize raid group size {for SAS max is 28 i guess} instead of default RG size 14. Also you can opt for Raid -4. This is will give you maximum space.

Can I use raid size 24?

This case all sas drive will fill up all the SAS,

Then I will create another aggregate with RG=14, here I will have 7*2.2TB SATA


You can but that will leave you with zero spares. If you are OK with that then go right ahead as 24 disk RAID groups are supported with SAS disks.


Paul  need maximum space,

WhaRG you will suggest me with spare disk.?

I will appreciate your help.


I wish I could provide a single definitive answer but in this case it all depends on the data being stored and how fast you get replacement disks or as the saying goes YMMV (Your Milage May Vary)

If the data can be easily recreated/recovered, then I would go with a 24 disk RAID-4 group,  Maximizes capacity but leaves you with no spares and if more than one drive fails, you lose all the data on the RAID group.

You could go with a 24 disk RAID-DP group, that way you could survive two drive failures and be OK, that woud seem to be the best option in your situation.  Create one aggregate with a 24 disk RAID-DP RAID group that would yeild approximately 10TB usable.  Then I would configure one aggregate using a 6 disk RAID-DP group that will yeild approximately 5.6 TB usable.

But this is assuming that you a) have your vol0 on 2 TB SATA and b) do not have any additional spare 2TB SATAs to act as spares because I don't like operating my controller without a spare for the RAID group that supports the filer's root vol.

And of course, that means you can get replacement drives within a short (next day at most) period of time.


Can I put root vol on RG24 RAID_DP and leave the SATA for other Data?

yes you can.