Re: Downgrade from RAID6 to RAID5

Thanks Jim.

Don't have an EXP24 on the shelf at the moment :-)

As there are only 5 drives currently in the RAID6 set I am hoping the
manual estimate of 30 minutest to unprotect and 4-6 hours to do the RAID5
striping is close to the mark.

My reading suggests ipl to DST, and work with disk units and stop parity
protection which should take less than an hour the start parity
protection, select RAID5 and the drives and wait ...

And yes I am well aware that the system is unprotected until the RAID5
striping completes!!

Any other words of wisdom ?

Don Brown





From: "Jim Oberholtzer" <midrangel@xxxxxxxxxxxxxxxxx>
To: "Midrange Systems Technical Discussion" <midrange-l@xxxxxxxxxxxx>
Date: 25/11/2017 12:50 AM
Subject: Re: Downgrade from RAID6 to RAID5
Sent by: "MIDRANGE-L" <midrange-l-bounces@xxxxxxxxxxxx>



Yes I've done it several times. FULL BACKUPS with VERIFIED results that
everything is on tape. Turn off RAID6, then turn on RAID5. Takes a long
time to build the RAID striping. The system will be unprotected during
that time.

Assuming you cannot take the time (it'll be a full weekend depending on
how much storage you have) you could hang an expansion chassis on it with
sufficient disk, start RAID5 on that and migrate the system. Last step is
to copy the load source. Then re-raid your original disk to RAID5, and
migrate the system back if you wish to. If done that before too where
I've provided the hardware temporarily to get the job done. Total down
time with both load source migrations, about 5 hours.

Jim Oberholtzer
Agile Technology Architects
Office: 414-433-4363
Cell: 414-915-1445
Sent from iPad

"I've learned that courage is not the absence of fear, but the triumph
over it. The brave man is not he who does not feel afraid, but he who
conquers that fear". -- Nelson Mandela

On Nov 24, 2017, at 12:53 AM, Don Brown <DBrown@xxxxxxxxxx> wrote:

Hi All,

Long story short.

Have a system at 7.3 with 6 x 139GB spinning disks RAID6 and a disk

write

performance issue.

As RAID6 will require three writes to update all striping and RAID5 will

need two theoretically converting from RAID6 to RAID5 should provide a
performance increase ?

There is no space for additional drives in this system - Mirrored pair

are

used in Asp02

SSD's is not an option because both IBM and IBM remarketing both do not
have any of the required drives for this model 8202-E4B

We are considering second hand SSD's but not a preferred option.

Has anyone changed the RAID configuration from 6 to 5 and have any
comments on the process ?

Thanks
Don Brown


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