I am currently in the process of moving my disks from ReiserFS to XFS. Does XFS formatted disks have the same capacity as ReiserFS. And will all files of a filled up ReiserFS disk fit on a XFS disk?

Good question.

 

I found this discussion of the usable space for various file systems:

https://www.debian-administration.org/article/388/Filesystems_ext3_reiser_xfs_jfs_comparison_on_Debian_Etch

 

The relevant info is:  "... Partition capacity

...  ReiserFS = 99.83%,  ...  XFS = 99.95%

 

So XFS actually allows slightly MORE of the disk's capacity to be used than Reiser.

 

... thus it would seem the answer to your questions are NO, the XFS formatted disks do not have the same capacity as ReiserFS (they have more);  and thus YES, all files of a filled up ReiserFS disk will fit on an XFS disk.

 

I am currently in the process of moving my disks from ReiserFS to XFS. Does XFS formatted disks have the same capacity as ReiserFS. And will all files of a filled up ReiserFS disk fit on a XFS disk?

No - the maximum size of a ResierFS system is 16TB (although disks of that size are not yet available), while XFS is much higher (I think of the order of 500TB).  That is one of the reasons that LimeTech are interested in getting XFS support into unRAID as disks of sizes greater than 16TB could well happen within the next few years.

 

As to whether the overheads are identical I think this is unlikely so as to whether all files from a 100% full formatted Reiserfs will fit on a similar size disk in XFS format it is not clear.    However I would have thought that  you could be reasonably certain a disk at 99% would copy OK.

I don't think the question related to the maximum supported disk size -- true that's going to be an issue for ReiserFS disks once disks > 16TB are available, but that's a different issue.    The question was whether or not the available space would be at least equal for an XFS volume, and based on the article I noted that answer is clearly yes.

 

in my quest to switch formats from reiser to btrfs, I had one disk that originally had under 2g free space, i was unable to copy the full disk, as there was 2.18gb used on a freshly formatted btrfs disk...... not sure on ifs though....

Btrfs is a different beast altogether...