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Understanding btrfs filesystem output

Dude!Oct 29 2012 — edited Oct 30 2012
Could someone please explain the following output:

It seems to me that btrfs fi df does not show the the total and available size disk space. What does the output actually mean? What is total, used and DUP?


[root@vm004 ~]# btrfs filesystem df /
Data: total=4.01GB, used=2.67GB
System, DUP: total=8.00MB, used=4.00KB
System: total=4.00MB, used=0.00
Metadata, DUP: total=1.00GB, used=141.72MB
Metadata: total=8.00MB, used=0.00


What does the following tell us. I guess 2.67GB + 142 MB = 2.81 GB?

[root@vm004 ~]# btrfs fi show
Label: 'root' uuid: e88be872-eb9b-482f-bac2-7bde7235d946
Total devices 1 FS bytes used 2.81GB
devid 1 size 15.84GB used 6.04GB path /dev/sda3

Why 6.04 GB used?

[root@vm004 ~]# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/sda3 16G 3.0G 12G 21% /
tmpfs 1004M 0 1004M 0% /dev/shm
/dev/sda1 485M 119M 341M 26% /boot

Thanks!
This post has been answered by Avi Miller-Oracle on Oct 29 2012
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Comments

BryanWood
You need to disable disk locking, which ordinarily is performed by the first VM to prevent any other VMs from corrupting your vmdk files via uncoordinated writes. You will have to shutdown both of your VMs and edit the *.vmx flat file for each, adding lines like the following (settings taken from workstation 6, but should be nearly identical settings for VM Player 3.x):

http://crosbysite.blogspot.com/2007/10/clustering-in-vmware-workstation-6.html

scsi1.sharedbus = "Virtual"
disk.locking = "false"
diskLib.dataCacheMaxSize = "0"
diskLib.dataCacheMaxReadAheadSize = "0"
diskLib.dataCacheMinReadAheadSize = "0"
diskLib.dataCachePageSize = "4096"
diskLib.maxUnsyncedWrites = "0"

A few comments:

- your shared disks (scsi1) must be on a separate virtual scsi bus than the boot disk (scsi0), to allow setting the sharedbus flag as seen above.
- you must also ensure the cache parameters and unsynced writes settings are set to guarantee that all IO is immediately flushed to the vmdk file so the other VM can immediately access the latest version of data.
1 person found this helpful
user8860348
Folks,

Hello. Thanks a lot for replying.

Because 2 Virtual Machines rac1 and rac2 share the same disk F:\VM_RAC\sharerac\asm1.vmdk and cause the problem, can we have rac1 and rac2 use different disks ?

For example,
Let rac1 uses disk F:\VM_RAC\sharerac\asm1.vmdk
Let rac2 uses disk F:\VM_RAC\sharerac\asm2.vmdk

If yes, how to have rac1 use asm1.vmdk and rac2 uses asm2.vmdk ?
BryanWood
Answer
Unfortunately no, Oracle RAC requires all nodes have access the same set of shared disks. If your database resides within ASM, each ASM instance (one per node) must also see the same set of disks to mount the ASM diskgroup containing the database's datafiles.

Best Regards,
Bryan Wood
Marked as Answer by user8860348 · Sep 27 2020
user8860348
Folks,

Hello. thanks a lot for replying.
I have edited the VMX files for rac1 and rac2. Both VMs can open at the same time now. Thanks again.
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Locked on Nov 27 2012
Added on Oct 29 2012
#linux, #oracle-linux
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