ThortonMellon
1 Copper

When can a SnapVX establish -both_sides option be used on an SRDF/A device group?

When can a SnapVX establish -both_sides command be used on an SRDF/A device group?

When attempting  said establish command, we get a invalid RDF state error, see below in red:

When querying the device group, it shows the RDF state as being consistent, see below in red:

symsnapvx -g "SDG02Srdf_Drclive" -name "VXW_BACPRE-Archive-Pre" -noprompt establish -both_sides

Establish operation execution is in progress for the device group SDG02Srdf_Drclive. Please wait...

The device is not in a valid RDF state for this operation

symrdf -g "SDG02Srdf_Drclive" query

Device Group (DG) Name       : SDG02Srdf_Drclive

DG's Type                    : RDF1

DG's Symmetrix ID            : 000197700110    (Microcode Version: 5977)

Remote Symmetrix ID          : 000197700111    (Microcode Version: 5977)

RDF (RA) Group Number        : 242 (F1)

        Source (R1) View                 Target (R2) View     MODE

---------------------------------    ------------------------ ---- ------------

               ST                 LI       ST

Standard        A                  N        A

Logical  Sym    T R1 Inv  R2 Inv   K Sym    T R1 Inv  R2 Inv       RDF Pair

Device   Dev    E Tracks  Tracks   S Dev    E Tracks  Tracks  MACE STATE

--------------------------------- -- ------------------------ ---- ------------

DEV001   007A8 RW       0       0 RW 005C8 WD       0       0 A.X. Consistent

DEV002   007A9 RW       0       0 RW 005C9 WD       0       0 A.X. Consistent

DEV003   007AA RW       0       0 RW 005CA WD       0       0 A.X. Consistent

DEV004   007AB RW       0       0 RW 005CB WD       0       0 A.X. Consistent

DEV005   007AC RW       0       0 RW 005CC WD       0       0 A.X. Consistent

DEV006   007F3 RW       0       0 RW 00613 WD       0       0 A.X. Consistent

Total             ------- -------             ------- -------

  Track(s)              0       0                   0       0

  MB(s)               0.0     0.0                 0.0     0.0

Legend for MODE:

(M)ode of Operation : A = Async, S = Sync, E = Semi-sync, C = Adaptive Copy

                     : M = Mixed, T = Active

(A)daptive Copy     : D = Disk Mode, W = WP Mode, . = ACp off

(C)onsistency State : X = Enabled, . = Disabled, M = Mixed, - = N/A

Consistency (E)xempt: X = Enabled, . = Disabled, M = Mixed, - = N/A

symdg show "SDG02Srdf_Drclive"

Group Name:  SDG02Srdf_Drclive

    Group Type                                   : RDF1     (RDFA)

    Device Group in GNS                          : No

    Valid                                        : Yes

    Symmetrix ID                                 : 000197700110

    Group Creation Time                          : Tue Apr  3 14:32:58 2018

    Vendor ID                                    : EMC Corp

    Application ID                               : SYMCLI

    Number of STD Devices in Group               :    6

    Number of Locally-associated BCV's           :    0

    Number of Locally-associated VDEV's          :    0

    Number of Locally-associated TGT's           :    0

    Number of Remotely-associated VDEV's(STD RDF):    0

    Number of Remotely-associated BCV's (STD RDF):    0

    Number of Remotely-associated TGT's(TGT RDF) :    0

    Number of Remotely-associated BCV's (BCV RDF):    0

    Number of Remotely-assoc'd RBCV's (RBCV RDF) :    0

    Number of Remotely-assoc'd BCV's (Hop-2 BCV) :    0

    Number of Remotely-assoc'd VDEV's(Hop-2 VDEV):    0

    Number of Remotely-assoc'd TGT's (Hop-2 TGT) :    0

    Number of Composite Groups                   :    0

    Composite Group Names                        : N/A

    Standard (STD) Devices (6):

        {

        -----------------------------------------------------------------------------------

                                                      Sym   Device                     Cap

        LdevName              PdevName                Dev   Config        Att. Sts     (MB)

        -----------------------------------------------------------------------------------

        DEV001                /dev/sdgy               007A8 RDF1+TDEV          RW      9218

        DEV002                /dev/sdgz               007A9 RDF1+TDEV          RW      9218

        DEV003                /dev/sdha               007AA RDF1+TDEV          RW      9218

        DEV004                /dev/sdhb               007AB RDF1+TDEV          RW      9218

        DEV005                /dev/sdhc               007AC RDF1+TDEV          RW      9218

        DEV006                /dev/sdjv               007F3 RDF1+TDEV          RW      9218

        }

    Device Group RDF Information

        {

        RDF Type                               : R1

        RDF (RA) Group Number                  : 242 (F1)

        Remote Symmetrix ID                    : 000197700111

        Number of Storage Groups               :    0

        Storage Group Names                    : N/A

        R2 Device Is Larger Than The R1 Device : False

        Paired with a Diskless Device          : False

        Paired with a Concurrent Device        : False

        Paired with a Cascaded Device          : False

        Thick Thin Relationship                : False

        RDF Pair Configuration                 : Normal

        RDF STAR Mode                          : False

        RDF SQAR Mode                          : False

        RDF Mode                               : Asynchronous

        RDF Adaptive Copy                      : Disabled

        RDF Adaptive Copy Write Pending State  : N/A

        RDF Adaptive Copy Skew (Tracks)        : 16383

        RDF Device Domino                      : Disabled

        RDF Link Configuration                 : Fibre

        RDF Link Domino                        : Disabled

        Prevent Automatic RDF Link Recovery    : Enabled

        Prevent RAs Online Upon Power ON       : Enabled

        Device RDF Status                      : Ready           (RW)

        Device RA Status                       : Ready           (RW)

        Device Link Status                     : Ready           (RW)

        Time of Last Device Link Status Change : N/A

        Device Suspend State                   : N/A

        Device Consistency State               : Enabled

        Device Consistency Exempt State        : Disabled

        RDF R2 Not Ready If Invalid            : Disabled

        Write Pacing Information

            {

            Pacing Capable                     : Yes

            Configured Group-level Exempt State: Disabled

            Effective Group-level Exempt State : Disabled

            Group-level Pacing State           : Disabled

            Device-level Pacing State          : N/A

            }

        Device RDF State                       : Ready           (RW)

        Remote Device RDF State                : Write Disabled  (WD)

        RDF Pair State (  R1 <===> R2 )        : Consistent

        Number of R1 Invalid Tracks            : 0

        Number of R2 Invalid Tracks            : 0

        RDFA Information:

            {

            Session Number                     : 241

            Cycle Number                       : 11582

            Number of Devices in the Session   : 6

            Session Status                     : Active

            Consistency Exempt Devices         : No

            Session Consistency State          : Enabled

            Minimum Cycle Time                 : 00:00:15

            Average Cycle Time                 : 00:00:15

            Average Transmit Cycle Time        : 00:00:15

            Transmit Queue Depth on R1 Side    : 1

            Tracks not Committed to the R2 Side: 0

            Time that R2 is behind R1          : 00:00:16

            R2 Image Capture Time              : Thu May  3 17:43:46 2018

            R2 Data is Consistent              : True

            R1 Side Percent Cache In Use       : 0

            R2 Side Percent Cache In Use       : 0

            Transmit Idle Time                 : 00:00:00

            R1 Side DSE Used Tracks            : 0

            R2 Side DSE Used Tracks            : 0

            R1 Side Shared Tracks              : 0

            }

        }

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8 Replies
SKT2
3 Zinc

Re: When can a SnapVX establish -both_sides option be used on an SRDF/A device group?

what is that you are trying to achieve by using -both_sides option? What is the need here?

in hypermax os you can't have snap and clone concurrently from a given source volume ( it is either snap or a clone); does that ring a bell for your setup?

also there is a -remote option along with symsnapvx if you are trying to do a restore on R1 while R2 is in consistent state. But I can see you are doing establish though..

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ThortonMellon
1 Copper

Re: When can a SnapVX establish -both_sides option be used on an SRDF/A device group?

The R1 side of our SRDF/A pair is our production database while the R2 side is our disaster recovery copy of our production database located thousands of miles away. On the R1 side we periodically take snapshots of the production database in order to create point in time copies from which we can restore from if necessary.

In case of a disaster where we completely lose the production data center where the production database resides, we currently rely on mounting up the R2 side copy of the production data base at the disaster recovery data center in order to continue processing from the disaster recovery data center.

Since the SRDF/A link can be up to 30 seconds behind replicating R1 data to R2 there is some potential data loss possible. In order to avoid possible data loss we currently create a remote clone off of the R2 side as a point in time copy whose contents coincides with one of the R1 snapshots made on the local side. So in case of a disaster, the R2 clone provides us a point in time copy of the database with no data loss due to SRDF/A replication delay.

What we like to do instead is use the SnapVX establish -both_sides option to create both a snapshot off of R1 and a snapshot off of R2 at the same time that will be identical.  The idea is that in case of a disaster we would restore the R2 snapshot back to the R2 side in order to continue processing. This would negate the need to use remote clones off of the R2 side all together.

So the real question is can SnapVX establish snapshots on both R1 and R2 at the same time when R1 and R2 are linked using SRDF/A, and if so, what state must the RDF link be in to execute the establish command as our first attempt show below failed?

symsnapvx -g "SDG02Srdf_Drclive" -name "VXW_BACPRE-Archive-Pre" -noprompt establish -both_sides

Establish operation execution is in progress for the device group SDG02Srdf_Drclive. Please wait...

The device is not in a valid RDF state for this operation

I hope this helps explain where we are coming from.

TL

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PedalHarder
2 Iron

Re: When can a SnapVX establish -both_sides option be used on an SRDF/A device group?

For the -both_sides option to be successful, the following conditions need to be met:

  • All devices in the group need to have the same RDF personality
  • The must be in the same RDF group
  • The RDF pair state must be Synchronous (or Active / ActiveActive or ActiveBias states for SRDF Metro)

I expect your SRDF/A mode is the issue. The above restrictions are documented in the SnapVX 8.4 product guide.

To get a successful -both_sides SNAPVX, transition to Synchronous mode beforehand and then back to SRDF/A mode after the snapVX.

PedalHarder
2 Iron

Re: When can a SnapVX establish -both_sides option be used on an SRDF/A device group?

Thanks for your explanation Thomas. Somehow your last response came to me after I replied above...

There is something I would like to pick up on regarding your current clone process. In the process where you take a clone of the R2 such that it coincides with an R1 snapshot. I guess that means that you clone the DB R1 to another R1 and take a snap of the cloned R2? That way you would have the same PIT on both sides. This would take time though as the data needs to be remotely replicated first. In the mean time the production database has moved on. In a DR, the SRDF/A R2 copy will hold the latest copy of the data. The clone will be somewhat behind that.

It sounds like you want or need a zero data loss extended distance DR capability.

The only way to achieve this would be a cascaded SRDF configuration R1>R21>R2. This is a 3 box solution where the R1>R21 is synch (metro distance) and R21>R2 is SRDF/A.

In the 3 site solution, because the first leg is synchronous, the R21 site will be equal to the R1. If there is an R1 DR, the SRDF/A leg will get the data up to the point of the outage (zero data loss).

ThortonMellon
1 Copper

Re: When can a SnapVX establish -both_sides option be used on an SRDF/A device group?

Thanks Jason for replying, I can always use another point of view when designing solutions, so yours is much appreciated.

Our current solution is controlled by our application which has the ability to put the database into a READ/ONLY mode

then flushes its data to disk before we activate the R1 VPSnap snapshot, which is then immediately followed by a

RDF Checkpoint of R1>R2 and activation the remote R2 clone. This solution has provided a zero data loss solution that has worked well for us for years.

Since we are now migrating to the VMAX All Flash Array hardware we want to take advantage of the SnapVX technology and use the SnapVX -both_sides option in order to replace the R2 clone we rely on today. Since we are always running in SRDF/A mode the application maybe able to set mode to synchronous while in READ/ONLY mode before establishing the SnapVX -both_sides option and then immediately setting the mode back to asynchronous, but so far I have not gotten that to work. Below is a first attempt using symsnapvx -both_sides in synchronous mode.

symrdf -g "SDG02Srdf_Drclive" checkpoint -nop -rdfg 242

... Waiting 23 seconds for the checkpoint ...

Check-point passed!

symrdf -g "SDG02Srdf_Drclive" disable -nop -rdfg 242

An RDF 'Disable' operation execution is in progress for device group 'SDG02Srdf_Drclive'. Please wait...

The RDF 'Disable' operation successfully executed for device group 'SDG02Srdf_Drclive'.

symrdf -g "SDG02Srdf_Drclive" set mode sync -nop -rdfg 242

An RDF Set 'Synchronous Mode' operation execution is in progress for device group 'SDG02Srdf_Drclive'. Please wait...

The RDF Set 'Synchronous Mode' operation successfully executed for device group 'SDG02Srdf_Drclive'.

symsnapvx -g "SDG02Srdf_Drclive" -name "VXA_BOTHSIDES" -nop establish -both_sides

Establish operation execution is in progress for the device group SDG02Srdf_Drclive. Please wait...

Cannot use the device for this function because it is a Copy Session source

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david_l1
1 Nickel

Re: When can a SnapVX establish -both_sides option be used on an SRDF/A device group?

Hi Tom - it looks like you still have a copy session occuring, do you still have VP snaps & clones in session on the devices?  You can't mix & match the modes with SnapVX.

If you want to discuss we can setup a call.

Thanks

Dave

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PedalHarder
2 Iron

Re: When can a SnapVX establish -both_sides option be used on an SRDF/A device group?

Agreed, You have passed your RDF mode issues now. I believe you said in an earlier post that you clone the R1. That may be the issue. There are a few KB articles on the error you have so should be overcome without too much trouble.

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Highlighted
ThortonMellon
1 Copper

Re: When can a SnapVX establish -both_sides option be used on an SRDF/A device group?

Dave,

I'm just getting back to this after being interrupted by higher priorities, sorry it took so long. I repeated the test, see below, where I put the RDF device group into synchronous mode before executing the symsnapvx establish command. The resulting message is "Cannot use the device for this function because it is a Copy Session source", so then I attempted the symsnapvx establish without the -both_sides option and that worked. So is this message telling me I have a copy session from the R2 side to a clone on the R2 side? If so, how do I identify the copy session so that I can terminate it? If you're still available to setup a call, that would be great!

symrdf -g "SDG02Srdf_Drclive" checkpoint -nop -rdfg 242

... Waiting 23 seconds for the checkpoint ...

Check-point passed!

symrdf -g "SDG02Srdf_Drclive" disable -nop -rdfg 242

An RDF 'Disable' operation execution is

in progress for device group 'SDG02Srdf_Drclive'. Please wait...

The RDF 'Disable' operation successfully executed for

device group 'SDG02Srdf_Drclive'.

symrdf -g "SDG02Srdf_Drclive" set mode sync -nop -rdfg 242

An RDF Set 'Synchronous Mode' operation execution is in

progress for device group 'SDG02Srdf_Drclive'. Please wait...

The RDF Set 'Synchronous Mode' operation successfully executed

for device group 'SDG02Srdf_Drclive'.

symsnapvx -g "SDG02Srdf_Drclive" -name "VXA_BOTHSIDES" -nop establish -both_sides

Establish operation execution is in progress for the device group SDG02Srdf_Drclive. Please wait...

Cannot use the device for this function because it is a Copy Session source

symsnapvx -g "SDG02Srdf_Drclive" -name "VXA_R1SIDE" -nop establish

Establish operation execution is in progress for the device group SDG02Srdf_Drclive. Please wait...

    Polling for Establish.............................................Started.

    Polling for Establish.............................................Done.

    Polling for Activate..............................................Started.

    Polling for Activate..............................................Done.

Establish operation successfully executed for the device group SDG02Srdf_Drclive

symrdf -g "SDG02Srdf_Drclive" set mode async -nop -rdfg 242

An RDF Set 'Asynchronous Mode' operation execution is in

progress for device group 'SDG02Srdf_Drclive'. Please wait...

The RDF Set 'Asynchronous Mode' operation successfully executed

for device group 'SDG02Srdf_Drclive'.

symrdf -g "SDG02Srdf_Drclive" enable -nop -rdfg 242

An RDF 'Enable' operation execution is

in progress for device group 'SDG02Srdf_Drclive'. Please wait...

The RDF 'Enable' operation successfully executed for

device group 'SDG02Srdf_Drclive'.

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