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Verifing that ATS is Configured on a Datastore in a VMware Support Bundle

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How do I verify if a datastore has Atomic Test & Set (ATS) configured properly in a VMware Support Bundle?

Confirming the SCSI-2 Reservations are Happening

If VMware is not configured as per best practice expectations (ATS Enabled) then we may see SCSI-2 Reservations in our logs.   This is how you can check to see if that's happening: 

  1. Run this command tgrep -c 'vol.pr_cache inserting registration' core* on Penguin Fuse on the date directory in question for the array, this will give you the number of SCSI-2 reservations created every hour:
    quelyn@i-9000a448:/logs/$ tgrep -c 'vol.pr_cache inserting registration' core*
  2. Running this command without the '-c' will allow you to see which LUNs are being locked, seen below bolded.  This can yield many lines of output, so you may want to do this per log file: 
    quelyn@i-9000a448:/logs/$ tgrep 'vol.pr_cache inserting registration' core*
    core.log-2015102700.gz:Oct 26 23:18:51.394 7FB1ACCF3700 I     vol.pr_cache inserting registration, seq 3097137672 vol 69674 i_t 20000025B5AA000E-spc2-0 res_type 15
    core.log-2015102700.gz:Oct 26 23:18:51.431 7FB1AD5F5700 I     vol.pr_cache inserting registration, seq 3097137673 vol 69673 i_t 20000025B5BB000E-spc2-0 res_type 15
    core.log-2015102700.gz:Oct 26 23:18:51.457 7FB1AE378700 I     vol.pr_cache inserting registration, seq 3097137674 vol 69662 i_t 20000025B5AA000E-spc2-0 res_type 15
    core.log-2015102700.gz:Oct 26 23:18:51.483 7FB1AE378700 I     vol.pr_cache inserting registration, seq 3097137675 vol 69661 i_t 20000025B5AA000E-spc2-0 res_type 15
    core.log-2015102700.gz:Oct 26 23:18:51.503 7FB1A73FC700 I     vol.pr_cache inserting registration, seq 3097137676 vol 69676 i_t 20000025B5AA000E-spc2-0 res_type 15
    core.log-2015102700.gz:Oct 26 23:18:51.522 7FB1AF7FD700 I     vol.pr_cache inserting registration, seq 3097137677 vol 69667 i_t 20000025B5BB000E-spc2-0 res_type 15
  3. You can then run the pslun command to determine the volume name: 
    quelyn@i-9000a448:/logs/$ pslun
    Volume Name                              pslun Name
    --------------------------------         ----------
    PURE-STR-LUN01                           pslun69648
    PURE-STR-LUN02                           pslun69660
    PURE-STR-LUN03                           pslun69661
    PURE-STR-LUN04                           pslun69662
    PURE-STR-LUN05                           pslun69664
    PURE-STR-LUN06                           pslun69665
    PURE-STR-LUN07                           pslun69666
    PURE-STR-LUN08                           pslun69667
    PURE-STR-LUN09                           pslun69668
    PUR-STR-LUN10                            pslun69669
    PUR-STR-LUN11                            pslun69670
    PURE-STR-LUN12                           pslun69671
    PURE-STR-LUN13                           pslun69672
    PURE-STR-LUN14                           pslun69673
    PURE-STR-LUN15                           pslun69674
    PURE-STR-LUN16                           pslun69675
    PURE-STR-LUN17                           pslun69676
    PURE-STR-LUN18                           pslun69677
    PURE-STR-LUN19                           pslun69678
  4. To determine which hosts are creating the SCSI-2 Reservations, we will need a VMware bundle.  The customer can send this to us via FTP.
  5. Once the bundle is uploaded, please prepare for analysis as per  KB: Retrieving Customer Logs from the FTP
  6. Run the vm script that jhop created against the bundles to check the global configuration of VAAI ATS Wiki: VMware vSphere Ovreview and Troubleshooting
  7. After we have confirmed that VAAI ATS is enabled globally if we are still seeing SCSI-2 reservations we will want to check each volume individually.  Please proceed to the next section:

Identifying datastore ATS Configuration on VMware ESXi

Step 1:

Since we only care about datastores (not Raw Device Maps (RDMs)) on Pure Storage we will find our applicable LUNs in the "esxcfg-scsidevs -m.txt" file under the "commands" folder in a VMware Support Bundle. Below is an example of what a line from there will look like:

Screen Shot 2015-12-03 at 2.43.59 PM.png

There are several things that we want to identify from this output; the first is the "NAA Identifier". This is important because anything starting with "naa.624a937" is a Pure Storage LUN. Once we have a Pure Storage LUN we then want to take note of the "VMFS UUID" number (i.e. 53c80075-7ddcc5ba-7d03-0025b5000080). The reason why we focus on this instead of the "User-Friendly Name" is because the customers can choose any name they want in that option. If we choose the VMFS UUID then we are guaranteed to know we are referring to a Pure Storage LUN since that is a uniquely generated ID that the vCenter Server assigns to individual LUNs. 

Step 2: 

Once we have this information the next step is to search for the "vmkfstools" text file that contains the File System information on this device; this will also be found in the "commands" folder you already reside in. An example of what the text file will look like is as follows:


Notice above our "VMFS UUID" is contained in the file name (in red). We can now search this file for the "Mode" it is running in. An example of what this line will look like, if configured properly, is as follows:

Mode: public ATS-only

If the datastore is not configured properly it will look as follows:

Mode: public

If the datastore is showing a "public" mode then we know that this datastore is misconfigured and we'll be receiving an excessive amount of SCSI-2 Reservations from the ESXi Hosts. This means that locking tasks are not being offloaded to the FlashArray. 

Obviously if the customer has a lot of LUNs this process above can take a while, so it is best to script this. I have listed below a simple one liner that will do this for you if you would like to use this instead of going through each LUN one-by-one:

grep "naa.624a937" esxcfg-scsidevs_-m.txt | awk '{print $3}' > Pure-LUNs.txt;while read f;do cat vmkfs*$f.txt |grep -e "Mode:" -e "naa.624a937";echo;done < Pure-LUNs.txt

NOTE: This command is able to be copied & pasted then used on any ESXi Host that is 5.0 and higher, as long as you are in the "commands" folder of the ESXi Host you want to verify. 


Once we have the misconfigured LUNs identified the customer can use the VMware KB listed below to resolve the issue:

Link to VMware KB:

Follow the steps outlined in the "Changing an ATS-only volume to public". Simply change the "0" they are setting to a "1" in the listed command they provide to turn ATS-only back on. It is important that the customer read all of the steps before continuing forward and reading the notes & caveats.

Alternatively, and also much less of a headache, the customer can simply create a new LUN from the FlashArray and mount it to the applicable ESXi Host(s). Once the new VMFS datastore is created they can verify that ATS is properly configured. Once confirmed the new datastore has ATS enabled can then migrate the Virtual Machines from the misconfigured datastore to the newly configured datastore. After everything has been moved from the old datastore and they have confirmed all is working well, they can simply destroy the old LUN. This is much easier to do and is typically what should be recommended as the first step. 

If there are any questions please reach out to a fellow colleague or Support Escalations team member for assistance.