List RAID Groups - VMAX

sympd list -v will show what disks volumes are on.  However a physical disk in Symmetrix may contain parts of many protection types.  One volume could be one of four in a 3+1 volume, another volume on the same drive could be one of two in a mirrored volume and yet another could be 1 of 16 in a 14+2 RAID6 volume.

"sympd list" will only lists the devices visible to the SAN host, where as "symdev -sid list -datadev" gets all the datadevs and it's physical disks. But I am after the RAID groups. I want to find out which datadev is on which RAID group.

On our VMAX we have 92 RAID groups(manually counted), But I wish to see a symcli command to list the devices by RAID group.

Thanx again.

-Shyam

What do you mean by "raid group"?  A logical volume is the only raid group concept in Symmetrix.

I am referring to raid5(3+1/7+1),raid6(6+2/14+2) RAID groups.

-Shyam

Those would be logical volumes.  Again, I could have all 4 of those along with mirrored volumes on the same drive.

Thanx Quincy. I thought the Raid Groups are similar to what we setup in CLARiiON. What I understand from the above pic is,the RAID Groups are actually created from logical volumes and not physical disks. Now my follow up question is, does "symdev" has an option to list these logical volumes from the RAID Group ?

Appreciated.

-Shyam

Yes, in CLARiiON a group of disks is given a specific protection.

You can see the backend info for any device with the symdev list -v command.  You need to add -datadev to see the TDATs

Here is the output from one of the systems in the lab. The disk ID is the first column.

    Back End Disk Director Information
        {
        Hyper Type                             : RAID-6
        Hyper Status                           : Ready           (RW)
        Disk [Director, Interface, TID]        : [N/A,N/A,N/A]
        Disk Director Volume Number            : N/A
        Hyper Number                           : N/A
        Mirror Number                          : 1
        Disk Group Number                      : 2
        Disk Group Name                        : DISK_GROUP_002
        }

    RAID Group Information
        {
        Mirror Number                            : 1
        RAID Type                                : RAID-6
        Device Position                          : Primary
        Protection Level                         : 6+2
        RAID Group Service State                 : Normal
        Failing Member Mask                      : N/A
        Hyper Devices:
            {
            Device : 01B8
                {
                ------------------------------------------------------
                 Disk     DA      Hyper        Member        Disk    
                DA :IT   Vol#  Num  Cap(MB)  Num Status  Grp#  Cap(MB)
                ------------------------------------------------------
                07B:D1A    294    7    2923    1 RW         2  1823565
                08D:C1A     90    7    2923    2 RW         2  1823565
                08A:D1A    295    7    2923    3 RW         2  1823565
                07C:C1A    100    7    2923    4 RW         2  1823565
                08B:C1A    114    7    2923    5 RW         2  1823565
                07D:D1A    300    7    2923    6 RW         2  1823565
                07A:C1A    120    7    2923    7 RW         2  1823565
                08C:D1A    304    7    2923    8 RW         2  1823565
                }
            }
        }

Great, Thanx again Quincy.

-Shyam

Just to reiterate what Quincy was saying, the whole concept of RAID Group does not exist at all on the Symmetrix platform. So in response to your clarifying statement, RAID Groups are NOT created from logical volumes.

I still remember the shift in thinking required when I went from CLARiiON platforms to work on Symms as well and this was one of those things that took the most effort to get straight. You can have Disk Groups on the Symm which help control which physical drives are used underneath a device. These often are differentiated by the types of drives (e.g. Disk Group 0 might be 300GB 15K FC drives while Disk Group 1 is 500GB SATA drives). Each of those drives can contain hypers (the individual boxes in Quincy's picture) and a device is made up of the appropriate number and size of hypers across the right number of drives. So a 33GB RAID5(3+1) STD device would be made up of 4 x 11GB hypers from four different drives in the same disk group. When devices are laid out they are done in such a way as to optimize performance by ensuring that all the hypers are on separate physical drives and even using separate back end director channels.

I am a bit confused by where the picture Quincy is using came from as I'm not sure why it references "RAID Groups" at all.

I refer to the disks that are grouped together to protect a logical volume in Symmetrix as a raid group.  So in the picture I posted, there are several raid groups on those physical disks.

That is not a recommended practice in real life.  With VMAX systems and VP pools, frequently an entire set of disks is assigned the same protection, so the Symm would look more like a CX then.

I understand where that's coming from Quincy. I guess in my case I just had such a rough transition to Symm from CLARiiON "thought" that I automatically try to avoid references that may confuse people new to one platform or the other. Any time I can use specific language that differentiates the platforms clearly I tend to stick carefully to that (e.g. devices vs. LUNs - and yes I know that LUN is typically misused as well, but for me it's always been the name for a "device" on a CLARiiON). That's just a "me" thing though :-)

No need to try and completely avoid using the term RAID Group with Symmetrix.  It's actually used quite a bit.  The VMAX Product Guide has several references to RAID Groups. 

Symmetrix will in effect create RAID Groups once a volume is created across a set of disks.  For example, once a RAID 1 device is created using 2 specific drives, the next RAID 1 device created on one of those drives will need to use the same other drive as it's pair.

But as Quincy illustrated each drive can have multiple types of protection configured on it.

I've noticed several things with the VMax that seem to stray from the hard and fast (well established) Symmetrix platform conventions of old. It's almost like they had a whole new set of engineers working on this product. I still find it somewhat conflicting when the same term is used for two entirely different concepts between the midrange platforms and the Symms. While "RAID Group" may be used to describe something on the VMax it isn't really the same thing as it is on a CLARiiON. It just makes it harder for folks who are transitioning from experience with one platform to fully grasp the concepts of the new platform without confusion.

Still just my personal pet peeve though :-)

Hi Allen,

Not sure about the other differences you have noticed, but this rule has actually been around for quite some time and is not new with VMAX.  It is designed to limit the exposure to dual RAID failures.

On Symm the "RAID groups" will be created dynamically as volumes are created depending on the the type of RAID protection requested and the hardware configuration (DA count, drive count/layout).

Mike