What do ns_quota and ds_quota mean in an namednode entry

[Bert Yuan]

Bellow is json format of an namednode entry:
{
    inode:{
        inodepath:'/anotherDir/biggerfile',
        replication:3,
        modificationtime:'2009-03-16 14:15',
        accesstime:'2009-03-16 14:15',
        blocksize:134217728,
        blocks:{
            numblocks:3,
            block:[
                {
                    blockid:-3825289017228345300,
                    numbytes:134217728,
                    generationstamp:1002
                },
                {
                    blockid:-561951562131659300,
                    numbytes:134217728,
                    generationstamp:1002
                },
                {
                    blockid:524543674153269000,
                    numbytes:18196208,
                    generationstamp:1002
                }
            ]
        },
        nsquota:-1,
        dsquota:-1,
        permissions:{
            username:'jhoman',
            groupname:'supergroup',
            permstring:'rw-r--r--'
        }
    }
}

I don't know what's the meaning of 'nsquota' and 'dsquota', could anyone
explain this to me?