FAS and V-Series Storage Systems Discussions

Re: OK to convert a Flash Pool from RAID-DP to RAID4?

AH HA, we're running 8.1.3, I thought this whole time we were on 8.2. I will upgrade to 8.2.1 today and try the command again.

Re: OK to convert a Flash Pool from RAID-DP to RAID4?

You want your data in Raid-DP, .. That's my opinion

Re: OK to convert a Flash Pool from RAID-DP to RAID4?

It worked! After upgrading to 8.2.1, the -T argument was accepted. Now the aggregate shows 372 GB Flash Pool!

Here's what I did:

This command changed the SSD raid group to raid4:

aggr options aggr0 raidtype raid4 -T SSD

"aggr status -r" showed two SSD spare disks. I added the specific SSD that used to be in the RAID-DP set because it was showing as not being zeroed-out:

aggr add aggr0 -g rg1 -d 0b.00.0

That command added another data disk to the RAID4 group after zeroing it out. The only negative I see so far is I can't edit the aggregate now in the System Manager, it says "This aggregate comprises mixed RAID type. You cannot edit aggregates having mixed RAID type."

I can live with that.

Re: OK to convert a Flash Pool from RAID-DP to RAID4?

Robert -

I had to wonder when the raid conversion worked on the sim for me.

Versions matter.

Another bit of errata for me to remember.

Glad to hear the change worked for you !

At your service,

Eugene E. Kashpureff

Independent NetApp Consultant, K&H Research http://www.linkedin.com/in/eugenekashpureff

Senior NetApp Instructor, Unitek Education http://www.unitek.com/training/netapp/

(P.S. I appreciate points for helpful or correct answers.)

Re: OK to convert a Flash Pool from RAID-DP to RAID4?

Looks like this thread has been closed for a while but I thought I would mention, our Netapp SE recommended that we use raid-dp instead of raid-4 and instead just add the spare disk into the aggregate(and turn off the notification of no spares if it complains).  The logic was that raid-DP would recover faster than raid-4 with spare, because the "spare" would already be hot.  Any thoughts on this?

Re: OK to convert a Flash Pool from RAID-DP to RAID4?

Mikker,

At least for FAS2200 series it is recommended to use RAID4 for flash pool.

From TR-4070

"On a FAS2200 series system that is running Data ONTAP 8.2, the recommendation is to configure the SSD RAID group with RAID 4 protection and one hot spare SSD. With this configuration, data is protected, and an immediate and fast RAID group rebuild occurs if a SSD fails. If RAID 4 protection is chosen for an SSD RAID group in a Flash Pool aggregate on any other FAS or V-Series system, at least one hot spare SSD should be maintained for each node that has a Flash Pool aggregate configured on it."

I have seen several recommendations to use RAID4 (2cache+1parity+1spare) instead of RAID-DP (2cache+2parity, no spare) but this goes about small boxes.

Re: OK to convert a Flash Pool from RAID-DP to RAID4?

As far as I know, the only way to disable low spare warning, is by setting the "raid.min_spare_count" option to zero. This is a global option and it will be valid for all the controller's raidgroups whether they are containing SSDs or not.

IMHO, it is certainly not a best practice.

Saying raid-DP would recover faster than raid-4 with spare, because the "spare" would already be hot, is an absolute nonsense.

Since the SSD is in the aggregate, it's not a spare disk, it's a parity disk. If one SSD fails, aggregate will be in a degraded condition with no spare to rebuild and you will not be warned of the low spare condition since you disabled it.

Re: OK to convert a Flash Pool from RAID-DP to RAID4?

Can you elaborate, our Netapp SE is still insisting that raid-dp would be best.  I get that we will not be warned about the low spare condition(which we hope to get past with proper monitoring, and as I understand it, the autosupport request for disk replacement would still work), but otherwise,  the failure condition seems the same(two disks can fail before we have data loss), and the recovery time seems like it would be faster on raid-dp. I don't see how it's "absolute nonsense"

Re: OK to convert a Flash Pool from RAID-DP to RAID4?

For Cluster Mode with 8.2 and higher:

 

Change Raid Group type for SSD disks on Hybrid aggr:

cl1:: > aggr modify -aggregate aggr_d01 -raidtype raid4 -disktype SSD

 

Then add the relised disk to the aggr:

cl1:: > aggr add-disks -aggregate aggr_d01 -disktype SSD -raidgroup rg1 -diskcount 1

Re: OK to convert a Flash Pool from RAID-DP to RAID4?

Thanks TREBOR2000! Your solution worked like a charm!

 

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