How to ensure data is going to right mount point

[powerserg19]

With this instance type i3en.xlarge I set the block device volume size to 250G(from default 30G) on root device "/dev/xvda" such that my application can download data from s3 . Is this allowable or should I do it on another device name? If I try another device name like /dev/xvdba the instance still goes down because I run out of storage space. I think its because I am not setting the mount point

=============volumes i3en.xlarge======================
sh-4.2$ sudo nvme list
Node             SN                   Model                                    Namespace Usage                      Format           FW Rev
---------------- -------------------- ---------------------------------------- --------- -------------------------- ---------------- --------
/dev/nvme0n1     vol046586ef43a35a957 Amazon Elastic Block Store               1           0.00   B / 268.44  GB    512   B +  0 B   1.0
/dev/nvme1n1     AWS151BEEA468A70CE26 Amazon EC2 NVMe Instance Storage         1           2.50  TB /   2.50  TB    512   B +  0 B   0
sh-4.2$ lsblk
NAME          MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
nvme1n1       259:0    0  2.3T  0 disk
nvme0n1       259:1    0  250G  0 disk
├─nvme0n1p1   259:2    0  250G  0 part /
└─nvme0n1p128 259:3    0    1M  0 part
sh-4.2$ lsblk -f
NAME          FSTYPE LABEL UUID                                 MOUNTPOINT
nvme1n1
nvme0n1
├─nvme0n1p1   ext4   /     d39c4828-5c41-4399-b4cf-b8f3812ac925 /
└─nvme0n1p128
sh-4.2$
============volume i3.xlarge=================
sh-4.2$ sudo nvme -list
Node             SN                   Model                                    Namespace Usage                      Format           FW Rev
---------------- -------------------- ---------------------------------------- --------- -------------------------- ---------------- --------
/dev/nvme0n1     AWS191F43D8A430BE68E Amazon EC2 NVMe Instance Storage         1         950.00  GB / 950.00  GB    512   B +  0 B   0
sh-4.2$ lsblk
NAME    MAJ:MIN RM   SIZE RO TYPE MOUNTPOINT
xvda    202:0    0   250G  0 disk
└─xvda1 202:1    0   250G  0 part /
nvme0n1 259:0    0 884.8G  0 disk
sh-4.2$ lsblk -f
NAME    FSTYPE LABEL UUID                                 MOUNTPOINT
xvda
└─xvda1 ext4   /     d39c4828-5c41-4399-b4cf-b8f3812ac925 /
nvme0n1