With respect to XFS Bitmap flush to disk
Dear All,
Recently, I try to read analyze the bitmap of XFS file system, it seems that I cannot read the latest bitmap from hard disk involving the XFS, and cannot read the accurate info even after a long time. For example, i cannot get the relevant bitmap info after I add/delete a big file to/from XFS file system.
I tried several solution, and find it out that I must execute xfs_freeze for the XFS partition in CentOS7, and it seems that xfs_freeze doesn’t work for XFS version included in Redhat6.5, I must umount/mount the xfs, then I can get the latest bitmap info related to the latest data located in disk.
What strategy does XFS use to cache/flush bitmap to hard disk? How can I get the accurate bitmap info especially for Redhat6 series Operating System? Could you please give help on it?
Thanks in advance! ☺
Halsey Pian
Quoted 2 lines · Halsey Pian
I tried several solution, and find it out that I must execute
xfs_freezefor the XFS partition in CentOS7, and it seems thatxfs_freezedoesn’t work for XFS version included in Redhat6.5, I must umount/mount the xfs, then I can get the latest bitmap info related to the latest data located in disk.
Why do you think that xfs_freeze does not work on el6?
Quoted 7 lines · Halsey Pian
Dear All,
Recently, I try to read analyze the bitmap of XFS file system, it seems that I cannot read the latest bitmap from hard disk involving the XFS, and cannot read the accurate info even after a long time. For example, i cannot get the relevant bitmap info after I add/delete a big file to/from XFS file system.
In general, attempting to read metadata from a mounted block device isn't going to be reliable. For one, changes may only be staged in the log, and not yet in their final disk location.
Quoted 9 lines
I tried several solution, and find it out that I must execute
xfs_freezefor the XFS partition in CentOS7, and it seems thatxfs_freezedoesn’t work for XFS version included in Redhat6.5, I must umount/mount the xfs, then I can get the latest bitmap info related to the latest data located in disk.What strategy does XFS use to cache/flush bitmap to hard disk? How can I get the accurate bitmap info especially for Redhat6 series Operating System? Could you please give help on it?
The short answer is "you can't." Directly reading the block device while mounted isn't a supported use of the filesystem.
What are you trying to do, here?
Thanks,
-Eric
Quoted 12 lines
Thanks in advance! ☺
Halsey Pian
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