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Open Migrator - Win 2K8R2 System process handle locking drive
I'm trying to do an online cutover of an iSCSI attached LUN to a VPLEX disk. We've been doing a bunch of these over the past few months without really any issues. We stop any required services, use Open Migrator to Complete Migration, then detach filter driver and reboot. If some service is running that we missed, the Complete Migration fails and tells us what is accessing the drive so we can stop it and try again.
On a Win 2008R2 server I attempted last night, there is a file handle that is open from the System process. Here is an output from handle on this server after we stopped all services:
C:\OM_Logs\Handle>handle t:
Handle v3.51
Copyright (C) 1997-2013 Mark Russinovich
Sysinternals - www.sysinternals.com
System pid: 4 type: File 5C0: T:\$Extend\$RmMetadata\$TxfLog\$TxfLog.blf
System pid: 4 type: File 5C4: T:\$Extend\$RmMetadata\$TxfLog\$TxfLogContainer00000000000000000001
System pid: 4 type: File 5C8: T:\$Extend\$RmMetadata\$TxfLog\$TxfLogContainer00000000000000000002
System pid: 4 type: File 5D4: T:\$Extend\$RmMetadata\$Txf
System pid: 4 type: File 1118: T:\
This System handle on T:\ (not the $Extend ones) prevented us from doing the cutover.
Can anyone shed some light on what would cause the System process to have a handle open on the root drive letter? I checked some other disks on the server including the OS system drive and I don't see a handle like this on it.
Via Process Explorer I can close the file handle, but not knowing what it is or what it is doing, I'm very uneasy about doing that.
rzero
58 Posts
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June 24th, 2014 07:00
Thanks for the info Mich, I hadn't actually seen that before. I found it odd because I've been doing OpenMigrator on Microsoft iSCSI attached LUNs for a while now. I raised this concern in an SR I had open and support says this is not accurate since OpenMigrator is volume based - it is also not mentioned anywhere in the product guide, only the release notes. I can see potential issues with the software initiator if you are trying the reboot method of cutover, but I am not (I actually very much dislike the reboot method...). If you have any information on what issues there are with Microsoft iSCSI I would like to hear more information.
That said, through a lot of testing I finally identified the culprit as NFS Server running on the box and having an active share on that drive. Once the share is connected to, Windows will run a filter driver on the root drive letter, as seen here:
c:\Handle>handle f:
Handle v3.51
Copyright (C) 1997-2013 Mark Russinovich
Sysinternals - www.sysinternals.com
System pid: 4 type: File 154: F:\$Extend\$RmMetadata\$TxfLog\$TxfLog.blf
System pid: 4 type: File 158: F:\$Extend\$RmMetadata\$TxfLog\$TxfLogContainer00000000000000000001
System pid: 4 type: File 15C: F:\$Extend\$RmMetadata\$TxfLog\$TxfLogContainer00000000000000000002
System pid: 4 type: File 168: F:\$Extend\$RmMetadata\$Txf
System pid: 4 type: File 343C: F:\
svchost.exe pid: 904 type: File 11C: F:\$Extend\$ObjId
svchost.exe pid: 904 type: File 160: F:\System Volume Information\tracking.log
C:\Handle>fltmc instances
Filter Volume Name Altitude Instance Name Frame VlStatus
-------------------- ------------------------------------- ------------ --------------------- ----- --------
msnfsflt F: 364000 MsNfsFsFilter Instance 0
luafv C: 135000 luafv 0
The only way I've found to get rid of the filter driver handle and still maintain your NFS shares is:
The downside is that the NFS shares are unavailable from step 2 through 7, but this will let you complete migration with NFS Server shares on a drive.
Edit: I forgot to include a list of things that DON'T stop the filter driver handle:
I wanted to post how I saw the filter driver since while I'm sure NFS Service on a Windows box is rarely run, this may apply to other things running filter drivers as well.
Mich
86 Posts
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June 22nd, 2014 16:00
Are you using the standard MS iSCSI initiator or an iSCSI HBA?
From the Open Migrator release notes:
iSCSI support
Open Migrator/LM V3.9 and above supports operations with iSCSI host bus adapters (HBAs). Open Migrator/LM does not support and
will not work under Microsoft’s iSCSI Software Initiator protocol.
Mich
86 Posts
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June 24th, 2014 15:00
I think you have basically touched on the major causes and why iSCSI was not supported. Filter drivers that hold locks. Will include File Shares, Virus Scanner products, Backup Agents, Server HW agents etc.
I found an old KB article https://support.emc.com/kb/32655 and when I enquired about this issue back in 2008 it was all related to the boot process. This was the discussion I had back then with engineering.
The iSCSI initiator is loaded after LDM in the boot process, according to Microsoft this is by design. The MS iSCSI driver creates volumes too late in the boot sequence for OM to migrate drive letters/expand the volumes after a migration.
So while it probably will work with most migrations, if you need to reboot to change drive letters or expand volumes, the product may not work.