[Lustre-discuss] Maximum OST Size

Andreas Dilger andreas.dilger at oracle.com
Mon Oct 18 13:59:36 PDT 2010


On 2010-10-18, at 14:47, Roger Spellman wrote:
> In Lustre 2.x, what is the largest number of files that we could possibly have?
>  
> I noticed that mkfs.lustre on the MDT passes the following parameters to mkfs.ext2:  -i 4096 -I 512

Do you mean the maximum OST size (as mentioned in the subject) or the maximum MDT size (above)?  For the ext4-based ldiskfs the maximum size is 16TB and 4B inodes (this listed in the manual).

> Can these params be smaller? 

For the MDT, yes, you could potentially use "-i 1500" as about the minimum space per inode, but then you risk running out of space in the filesystem before running out of inodes.  The "-I 512" parameter controls the size of the inode itself, which holds the xattrs.  If there are single-striped files and no use of ACLs, user_xattrs, etc. then you might get by with "-I 256", but if this xattr space is exceeded then each such inode will consume 4096 bytes of space and also be slower to access.

> Can we get more inodes if we use zfs?

Definitely yes.

Cheers, Andreas
--
Andreas Dilger
Lustre Technical Lead
Oracle Corporation Canada Inc.




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