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File size and Filesize on disk problem




I have a issue with a folder on a server that i am trying to backup.
The files are all various database and text files.
When i vies the propertys for this folder it shows that the size is 9.5GB, but the size on disk is 115GB !!!!

I am completely stumped, as we do not use any compression.
All the other folders on this drive are all ok. ed size 200gb size on disk 201gb.

Can anyone shed some light on this, or do i have a freak of nature !!!

The sizes should differ a bit, but that's alot! However looking at the number of files it doesn't look too wrong.

The reason is the way harddisks work. The harddisk is devided into clusters. Each cluster has a certain size (2k, 4k, 32k or so) equal to all the other clusters on the drive. A file cannot share a cluster with another file so if a file is only 20 bytes it will still take up a whole cluster (which can be say 32k).

With so many small files I suggest you remake the drive so it has as small clusters as possible. This will minimize the extra slack space wasted.

If this server is a Linux server I suggest you change file system to Reiser FS. I haven't used it myself but I've heard it recommended for systems with many small files (like news servers).



I cannot change the cluster size as this is on a 10tb san. (it may take a while to re-format) ;)
I will just have to hope that i do not get any more data like this..

I managed to back it up with Veritas backup exec, although it reported that it had backed up 20gb ??

I think a test restore is needed :D
The backup tape is probably using smaller "clusters" as performance is not such an issue with tapes. :) Small clusters makes for more reads/writes -> less performance.

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