[lustre-discuss] [EXTERNAL] Mounting lustre on block device

[Andreas Dilger]

On Mar 16, 2023, at 17:02, Jeff Johnson <jeff.johnson at aeoncomputing.com<mailto:jeff.johnson at aeoncomputing.com>> wrote:

If you *really* want a block device on a client that resides in Lustre you *could* create a file in Lustre and then make that file a loopback device with losetup. Of course, your mileage will vary *a lot* based on use case, access, underlying LFS configuration.

dd if=/dev/zero of=/my_lustre_mountpoint/some_subdir/big_raw_file bs=1048576 count=100000
losetup -f /my_lustre_mountpoint/some_subdir/big_raw_file
*assuming loop0 is created*
some_fun_command /dev/loop0

Note with ldiskfs backends you can use "fallocate -l 100000M /my_lustre_mountpoint/some_subdir/big_raw_file" to reserve the space.

Alternately, if you have flash-based OSTs you could truncate a sparse file to the full size ("truncate -S 100000M ...") and format that, which will not consume as much space but will generate more random allocation on the OSTs.

Disclaimer: Just because you *can* do this, doesn't necessarily mean it is a good idea

We saw a good performance boost with ext4 images on Lustre holding many small files (CCI).  Also, I recall some customers in the past using ext2 or ext4 images effectively to aggregate many small files for read-only use on compute nodes.

Cheers, Andreas


On Thu, Mar 16, 2023 at 3:29 PM Mohr, Rick via lustre-discuss <lustre-discuss at lists.lustre.org<mailto:lustre-discuss at lists.lustre.org>> wrote:
Are you asking if you can mount Lustre on a client so that it shows up as a block device?  If so, the answer to that is you can't.  Lustre does not appear as a block device to the clients.

-Rick



On 3/16/23, 3:44 PM, "lustre-discuss on behalf of Shambhu Raje via lustre-discuss" <lustre-discuss-bounces at lists.lustre.org<mailto:lustre-discuss-bounces at lists.lustre.org> <mailto:lustre-discuss-bounces at lists.lustre.org<mailto:lustre-discuss-bounces at lists.lustre.org>> on behalf of lustre-discuss at lists.lustre.org<mailto:lustre-discuss at lists.lustre.org> <mailto:lustre-discuss at lists.lustre.org<mailto:lustre-discuss at lists.lustre.org>>> wrote:


When we mount a lustre file system on client, the lustre file system does not use block device on client side. Instead it uses virtual file system namespace. Mounting point will not be shown when we do 'lsblk'. As it only show on 'df-hT'.


How can we mount lustre file system on block such that when we write something with lusterfs then it can be shown in block device??
Can share command??











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------------------------------
Jeff Johnson
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Aeon Computing

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Cheers, Andreas
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Andreas Dilger
Lustre Principal Architect
Whamcloud







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