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Force RG to raid5dp on VA7400

Nancy Stout
Frequent Advisor

Force RG to raid5dp on VA7400

I have 30 73G 10rpm drives. I am told one of the RG is at raid5dp I want to push the second RG to raid5dp also. How big of a lun would I need to create. RG1 has 264.388GB available space and RG2 has 263.494GB available space.

Also about how long would it take to copy the data to raid5dp.
9 REPLIES
Tim D Fulford
Honored Contributor

Re: Force RG to raid5dp on VA7400

Hi

o 73 GB disks actually bringa bout 66GB of isable space
o RAID5DP uses 2 disks worth of space as parity
o RAID5DP requires a minimum of 10% in RAID1+0
o RAID5DP also removes the number of active hot spares

So RG1 with 16 73GB disks 1 AHS in R5DP
66*.9*(16-3) ~ 770GB in R5DP
So RG1 with 16 73GB disks 1 AHS in R10
66**.9*.5*16 ~ 445GB in R10

RG2 with 14 73GB disks 1 AHS in R5DP
66*.9*(14-3) ~ 653 GB in R5DP
So RG2 with 14 73GB disks 1 AHS in R10
66*.9*.5*14 ~ 415 GB in R10

I would not actually NOT assign everything in R5DP, but assign slightly more than all RAID10 threashold (unless you definitely require the sapce).

Regards

Tim
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Tim D Fulford
Honored Contributor

Re: Force RG to raid5dp on VA7400

oops

look at "armdsp -a
Tim
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Nancy Stout
Frequent Advisor

Re: Force RG to raid5dp on VA7400

Tim,

Last month we had a disk failure which basicly took our system down. Then not knowing it was puting everything in raid 5 the disk was removed. We were down for 3 days during the recovery. I want to eliminate this from happening again by pushing it into raid 5 so it won't have to do a rebuild if I have another failed drive.

The disk setting from armdsp is auto include on, auto rebuild on, hot spare automatic, Max drives per loop pair and sybsystem is 105.
Tim D Fulford
Honored Contributor

Re: Force RG to raid5dp on VA7400

Nancy

Sorry for taking a week or so to get back to you. It sounds like you are stuffed.. The auto-include etc will not stop the system protecting itself during a faulire, it will only stop the system from re-leveling the disks after a new one has been replaced.

From what you say it sounds like you are running in RAID1+0 mode rather than HPAutoRAID. If so switch.. it can be done on-line. I would also advise going to the latter F/W HP19 on the controllers and HP05 on the DS2405 (I dont know what the disks should should be off the the top of my head).

HPAutoRAID is probably better for you because the RAID1+0 to RAID5DP conversion can use the efficient "log structered write" which is not available in RAID1+0 mode. We have also had similar problems, hence all our systems are in HPAutoRAID mode even though we ensure the system only uses RAID1+0 (e.g. make the LUN size <= 30% of raw size).

From the sounds of it it may be worth totally re-building your system (back-up, trash va, re-build va, & restore data) than doing any admin on it may take days to go through the levelling process.

Regards

Tim

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Tim D Fulford
Honored Contributor

Re: Force RG to raid5dp on VA7400

Hi.. I'm doing a Lt Columbo here... just one thing

look at armperf -c ARRAY -x COMMA -s -e > .csv

there is a set of colums there that say what the RAID5DP & RAID10 allocation is over time.

Regrads

Tim
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Nancy Stout
Frequent Advisor

Re: Force RG to raid5dp on VA7400

Tim,

The system is already in autoraid format. While we are looking at deciding what to do (most likely convert to raid 1+0 mode and restore all data) in the meantime I have been instructed to increase the size of the RG that is mostly in raid1+0 and make it raid5dp so that if we loose another drive we will not be down for an extended period of time while it restructures the data. My boss wants this done after hours so there is no possible down time if a disk is lost. This appears that it will be done this weekend.
In looking at armperf how do I read what it is telling me.
Tim D Fulford
Honored Contributor

Re: Force RG to raid5dp on VA7400

Nancy

I'm not sure I understand, or this does not make sense.

1 - Long term; you plan to move to RAID1+0 (I'd do this by leaving the setting as HPAutoRAID, but simply shrink the LUNs such that they are less than about 30% of the advertised size, so in total 30x73GB should give less than 650 GB, we use 25% e.g.545 GB)

2 - Short term; you want to add an appropriate size LUN to force system into RAID5DP. (numbers as above)

1 & 2 are exactly the opposite!!! have I got this right???

As far as reading the armperf simply run the cmd & ftp the output onto your PC & use M$ Excel to read the csv file. There are headders so you can see what is what.

Regards

Tim
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Nancy Stout
Frequent Advisor

Re: Force RG to raid5dp on VA7400

Tim,

On my 30 drives I have created 20 luns 30G in size that are split between 2 systems. The third system has 20 15G luns created. The system was created in AutoRaid. The database admin wants most of the data kept in raid1+0. At the present time we are over the threshold that would allow us to keep the data this way in RD1 and are very close to going over on RD2. Until we can buy more hardware we want to make everything raid5dp so that if we have another disk failure we will not be down while it converts the data. Therefor I will need to create an addition Lun on RD2 so that we can force a convert at a time of our choosing. My question is should I create a 73G lun or what size and can I not assign it to a system for the convert to take place, and about how long would it take to do the convert?
Tim D Fulford
Honored Contributor

Re: Force RG to raid5dp on VA7400

Nancy

I thgink I understand your previous thinking now...

> On my 30 drives I have created 20 luns
> 30G in size that are split between 2
>systems
So this means two systems consume 600GB

> The third system has 20 15G luns created
The third system has 300GB; bringing the total to 900 GB.

> The database admin wants most of the
> data kept in raid1+0.
Very sensible IMHO

> At the present time we are over the
> threshold that would allow us to keep
> the data this way in RD1 and are very
> close to going over on RD2
I do not know what you mean by RD1 & 2. I'm assuming you mean redundancy group RG1 & RG2. if so I think you are saying all 900GB lives in RG1. so calculator out and doing calculation for RAID5DP
o 66*(16-2)*0.9 is 831GB
900 into 831 doesnt go, and this is with NO active hot spare disks.... No wonder the va took a long time to recover. (BTW the 66GB per disk is a conservative figure, but I still do not think RG1 can hold 900 GB of data).

> Until we can buy more hardware we want
> to make everything raid5dp so that if we
> have another disk failure we will not be
> down while it converts the data
OK

> Therefor I will need to create an
> addition Lun on RD2 so that we can force
> a convert at a time of our choosing
OK so RG2 is empty

> My question is should I create a 73G lun
> or what size and can I not assign it to
> a system for the convert to take place
If RG2 is TRUELY empty then you need to creae a minimum of
66*14/2 = 462 with ActiveHot spare =0. I would create 500 GB to be safe as my figure of 66GB is conservative. .. the limit would be about
o 66*(14-2)*0.9 = 713 0 Active Hot Spare AHS
o 66*(14-3)*0.9 = 653 1 AHS
o 66*(14-4)*0.9 = 594 2 AHS

> and about how long would it take to do
> the convert?
If RG2 is empty then the LUNs will take no time (minutes) at all to be created. Puerly in space terms you should create about 500-600GB of LUN space in RG2 & migrate your data from RG1 to RG2 accordingly. I would then delete some of the LUNs in RG1 So that you have about 600GB of LUNs. The ideal (for performance) would be that each system has a similar number of LUNs from each redundancy group. e.g. system, 1 has 10 30GB LUNs ins RG1 & 10 30GB LUNs in RG2, and so on. The problem you face the the data migration. That I'm afraid is something only you can answer. Look at how long it takes to do a full backup and it will take a similar time or more to do the restore. Unless you have bought the business copy tool/licence the VA will not be able to migrate data for you. If you have bought the business copy tool, then you will need to find someone else to answer your question as I've had no experience with this!!!

Regards

Tim
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