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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
}
}
SKT2
2 Intern
2 Intern
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1.3K Posts
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May 4th, 2018 08:00
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..
ThortonMellon
12 Posts
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May 4th, 2018 12:00
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
PedalHarder
465 Posts
1
May 6th, 2018 18:00
For the -both_sides option to be successful, the following conditions need to be met:
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
465 Posts
1
May 7th, 2018 16:00
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
12 Posts
0
May 8th, 2018 14:00
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
Anonymous
5 Practitioner
5 Practitioner
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274.2K Posts
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May 9th, 2018 08:00
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
PedalHarder
465 Posts
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May 9th, 2018 16:00
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.
ThortonMellon
12 Posts
0
June 18th, 2018 06:00
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'.
mallilinux
7 Posts
0
October 25th, 2019 08:00
Hi Mellon,
Any breakthrough you found from EMC and how to achieve 0 RPO using snapvx if srdf/a?
Much appreciated for the steps.
Thank you.