Its a story told many times…..
You order a new storage solution and the world is good.
It’s lovely, it’s new and it offers mountains of new disk space…. but then… you…. fill it up!
So its off to order some new disks.
The order is in, the order is filled, the disks arrive.
What next? How about we just stick them in?
By just inserting the new disks, they will be made available to configure into RAID arrays from the Internal tab of the Physical Storage Group.
If the drives are showing as Unused, mark them to be Candidate. If they are already showing as Candidate (like most of the disks in my example below), then you are ready to hit the Configure Storage button and follow the guidance of the Wizard.
Of course maybe your enclosures are all full. In this case it’s time to order another enclosure (remember we can have up to 10). Once you have racked the enclosure up and cabled the new enclosure to the correct SAS Chain, then use the Add Enclosure menu item shown below to kick off the configuration:
Aussie Storage Blog 
Hi Anthony is it possible to expand an existing mdisk, add a candidate disk to an existing mdisk configured in RAID5 with 5 disks?
Hi Miguel.
Right now you cannot do that. Ideally add enough disks to a pool to create a new MDisk.
Array transformation is on the roadmap but you would need to talk to your local IBM Rep to get more details.
hi guys
I know this was asked but on 2011, now 2013….
is it possible to extend an mdisk lets’ say RAID 5, adding 1 or 2 more hard drives?
thanks
No its not. SVC does not support MDisk expansion and so neither does Storwize V7000. The only way to do this is to remove an array from a pool and then create a new array with the now free disks and your new disks.
yeah that’s the way but who has a lot of drives just waiting for this to happen…
I cannot create a RAID 5 array with more than 8 disks. How do I create it with more disks. The GUI only allows 8 disks in an MDISK. Can you help?
You are correct Ryan in that the GUI only offers 8 drive RAID5 arrays.
To create larger arrays (up to 16 drives), you need the use the CLI.
Lets take a simple example, you have 16 drives and you want to create a single array, do this:
GET THE DRIVE IDS:
svcinfo lsdrive
CREATE A POOL (change the name from ‘Pool’ to something else)
svctask mkmdiskgrp -ext 256 -guiid 0 -name Pool -warning 80%
CREATE A SPARE (change the ID to one you want to use):
svctask chdrive -use spare 23
CREATE THE ARRAY (change the pool ID, in this example ‘4’ to the pool ID created when you made the pool):
svctask mkarray -drive 0:22:20:19:18:17:16 -level raid5 -sparegoal 1 4
Hi Anthony,
need your advise on adding capacity to the current pool, Currently our V7000 is configured with 1 raid10 pool and 1 raid 5 pool with 5 HotSpare, now we need to configure only 2 Hotspare and another 3 drive need to add to existing pool which is RAID 5 pool, when I try to configure storage, select preset as raid5 and choose expand existing pool, the GUI only list the RAID10 array to choose, if I select preset as raid10, the GUI will list only raid 5 pool to choose. why this happen?
our objective is to add the 3 drive to raid5 pool and expand one of the volume…any other way to expand the pool size?
Curious behaviour, am not sure whats going on there. You could definately try the CLI to get this done.
Hi Anthony, Looking to purchase a v7000 with 120 drives instead of 240 for financial considerations. My question is related to how the v7000 creates its raid groups. On other storage systems, I would order the 10 disk shelves populated with 12 drives a piece. I’m not sure which would be better, that solution or just ordering 5 fully populated shelves. I know at some point in the future I would want to add additional storage. I’m not sure if the v7000 lets you choose the drives to create an (array/mdisk) or if it only handles the creation. If it would allow me to create my (arrays/mdisks), I would think it would be better to go down shelves, rather than across shelves for creation… thoughts? Thanks
I like the idea of ordering shelves that are not fully populated. It makes for much quicker and easier upgrade with less lead time.
When creating the arrays, you cannot choose the disks from the GUI… you would need to use the CLI to do that.
But there is no real availability or performance benefit in doing striping across enclosures, just let the GUI decide.
hi guys
I know this was asked but on 2011, now 2013….
is it possible to extend an mdisk lets’ say RAID 5, adding 1 or 2 more hard drives?
thanks
Hi Anthony, when we create arrays with the CLI or GUI, do we need to “balance” the drive selections between chain1 and 2? Is this even possible or not an issue? Thanks.
It’s not really an issue. You can create balanced. raid10 if you want. Otherwise don’t worry about it
Hi Anthony!
After searching in all documentation i don’t find any recommendation for populating the enclosures with new disks. Our Storwize v7000 has 3 enclosures, and is populated in this way http://s16.postimg.org/t2rnun6zp/Untitled.png. We want to install 6 new hard drives, 5 in raid 5 and one as spare and we don’t know if is good to put all six in same enclosure or to mix them to all enclosures. The second variant comes from a guy with some experience with IBM storages, but i personally don’t see any logic. Please tell me your opinion. Thanks.
Marius.
Marius, As your storwize, logically, uses 2 SAS chains and your Enclosure is spread between them – than yes more logical to spread them between 2 Expansions as you will have more balanced load on the drives due to distribution between 2 SAS channels.
Hi Anthony!
I have a pool and want to expand the pool is created with 5 arrays of 900GB in raid 5 I have bought 16 discs of 1.2 TB and I want make 2 matrices of 8 discs in raid 5 to expand my pool but the pool in the gui does not appear to do expand. What can I do?
Hi.
The trick is to make the arrays and add them to an existing pool at the end. I always use custom array so I can control where to add them to.
I have a pool, on storwize v7000, with mdisks(RAID10). Can i add to this pool mdisk with balanced RAID10?
You sure can
Hi Anthony, quick question :)
I have a storwize v7000, one Pool created with 5 mdisks configured in RAID5 ( one mdisk with 4 SSD drives, 4 mdisks with SAS drives, from these 4, 2 have 8 drives and the other 2 have 7 drives).
Now i have bought 5 additional drives, the ideal scenario was to expand the mdisks created, but as per my understanding that can’t be done right?
So i was trying to create a new mdisk with the new drives and assign it to the existing pool, unfortunetly it just let’s me create a new pool.
Any ideas? Is there a minimum of drives or something?
Thanks in advance
Francisco Batista
francisco.batista1978@gmail.com
With V7000 each RAID array is one MDisk.
You cannot resize an existing MDisk with more drives as the SVC code does not allow MDisks to grow.
So you are correct to create a new MDisk (RAID array) with your new drives.
I am unsure why the GUI wont let you add it to an existing pool, are you using Automatic or Manual creation?
Worst case you can definitely use the CLI to add it to the pool
Hi Anthony. I still find it a bit confusing to use the pools and the MDisk.
In my case I have a V7000 with 7.4 microcode, an a pool with three MDisk formed by 600GB HDs in R5
I have released eight 900GB hard drives, I created an R5 MDisk with them but I cannot add to the existing pool. What interests me is to extend the existing Pool adding the 900GB MDisk because I need to expand volumes of several host and have no space.
Is it right what I’m doing?
Thanks
Hi there.
The GUI is trying to stop you doing this because you are trying to expand a pool with non-matching disks.
You can do this in the CLI if you really want to but you will have a mix of drive types in the same pool.
Why is this a bad thing? If the drive types are the same speed, its not so bad, but even so, the number of extents on a number 600 GB vs 900 GB disk is different so you will end up with more data on less spindles.
You have two choices.
1) Use CLI to create a new array in the existing pool.
It would look something like this:
lsdrive –> get all the IDs of the new drives
lsmdiskgrp –> get the ID of the existing pool
Then make the array using the drive IDs (in this example 0 and 22 and 20 etc) and the pool ID (in this example pool ID 4)
Note I also use RAID 5 here… you may want some other RAID. I also set spare goal to 1.
svctask mkarray -drive 0:22:20:19:18:17:16 -level raid5 -sparegoal 1 4
2) Create a new pool and migrate some volume to it (so you can resize them). You can do all this from GUI
If you are trying to add a new array (MDisk) to existing pool, where the disks in the new array (MDisk) are the same as the disks already in the pool then you are doing the right thing.
As I said, fit the GUI wont help you… use CLI.
Finally I created a new pool with 900GB disks. I have divided the volumes between groups.
Thank you very much for your help.
Overall I found this and many blogs by my Aussie mates, very useful. I’m also a fairly big fan of IBM storage, but then again its what I mostly work on too. I find it odd after this many years the SVC code does not allow dynamic mdisk/raid array expansion. The statements of, gee how many people have free disks, or simply create another one doesn’t hold make sense to me. I think when adding more disks, to get more space, you want to maximize the amount of space you can use. This is not usually the case when creating new RAIDs (except 0,1,10) on new disks, because it invokes new overhead. Whereas opposed to adding additional disks to existing RAIDs (5,6) the overhead is already accounted for previously. If I have a 5 drive RAID 5 and I want to double the effective usable space I should be able to add 4 drives to it. Not add 5 more in a new RAID 5 array. This seems silly to me and nothing remotely new as many other, including IBM, storage has done this for numerous years.
I totally agree.
MDisk expansion has not existed in the code base since 2003. Sigh….
Here you can vote to include feature of adding disks to an existent mdisk/array https://www.ibm.com/developerworks/rfe/execute?use_case=viewRfe&CR_ID=22769
Anthony, We have a question related to V7000. the customer is running out of disk space and we only have 2 empty disk slots left in the enclosure. the customer has purchased 2 disks (300gb each) and wants to add them to an existing POOL consisting of RAID 10 mdisks. Can we add them to an existing Mdisk which will give the customer an extra 300gb space. We have tried but the V7000 will only allow us to add it as a raid 0 Mdisk without protection which is not what the customer wants. He would like to add them as raid 1 mdisk. Is this possible, if so what is the procedure.
add only ibm disk’s with special firmware?
It looks like dev went with D-RAID (XIV code?) rather than messing with the ServeRAID tools to restructure the underlying arrays.
Hi,
New to the v7000 Gen2 world and have some storage to configure. Unfortunately, I didn’t have any input in the purchase phase and I am working with what I’ve got. I have read some of the chapters in Rebooks pertaining to the v7000 and its features.
I have a controller and expansion shelf (there are other expansion shelves but I am not concerned with the config of those) with a mix of SSD’s (4*800Gb) and 44 10k 600Gb SAS disks.
The SSD’s will slot into the controller along with 20 of the SAS disks, the expansion shelf will be filled with the remaining SAS disks.
My query is around the configuration of EasyTier and Storage Pool.
40 of the SAS disks will be in RAID 10; 2 will be hot-spares, and two will be unused for the purposes of being able to add additional flash to the controller should we need it. I have read for best performance, flash should be installed into the controller. I doubt we will buy more flash anytime soon but I have calculated our storage requirements and we don’t need the additional space from 2 extra drives in the raid 10.
I am unsure how to best configure (RAID wise) the SSD’s for use in the EasyTier Storage Pool. I don’t really understand how the EasyTier pool handles the total loss of one of its mdisks. Would the data(extents) on that particular mdisk be unavailable(lost), i.e. LUNS with hot data on the SSD tier?
How would you configure the SSD’s with the caveat of must be able to sustain at least one disk failure?
Regards,
David
Your SSDs need to be in RAID config or an SSD failure will cause data loss. So raid1 or 5 is the go for an SDD array
Easy Tier moves extents. It does not mirror them.
Loss of an mdisk is loss of the data that was on it.
That usually means loss of the whole pool.
For read-mostly storage (most storage), RAID-5 is fine for the SSD tier.
If you have more than about 25% write, AND your hot data will fit, then you’ll want RAID-10.
Also note that the SAS disks will NOT hot-spare for the SSD tier. With only 4 DDMs, you can do a 2+P+Q, 2+P+S, or 3+P, or 2+2.
I’m a fan of RAID6 for no hot-spares, no cold spares, but you can also do RAID5 and keep a couple of hot spares handy.
Also, consider DRAID for your SAS mdisk. DDM rebuild after loss is faster.