Thanks for the replies.
I did some tests with "mkfs.lustre --mdt" command from ieel2 release. On my VMs it uses 1 inode per 4k bytes.

I recall using 1 inode per 2k bytes in the past(ie. lustre 2.1) for MDT volumes. I can override the defaults but perhaps there is a good reason for the change.

regards,
chris hunter

On Mar 27, 2016 2:23 AM, "Dilger, Andreas" <andreas.dilger@intel.com> wrote:
Right, the new default is 1 inode per 2048 bytes of MDT space (512M inodes per TB). This is as low as we are comfortable to go by default, since the way the filesystem is used can vary a lot.

If you know the environment better (e.g. have an existing filesystem and can measure MDT space used / inode used), and MDT space is precious then you might tune this a better for your environment.

Cheers, Andreas

> On Mar 25, 2016, at 09:27, Bob Ball <ball@umich.edu> wrote:
>
> Just as a data point, we have a 750GB ldiskfs RAID-10 combined mdt/mgs volume, that default formatted out to ~525M inodes.  This is Lustre 2.7.0.  I believe Lustre used 1 inode per 2048 bytes.
>
> bob
>
>> On 3/25/2016 11:03 AM, Chris Hunter wrote:
>> Hello,
>> I had an enquiry about appropriate number of MDS & MDT volumes for a
>> filesystem that could potentially hold 4bn files. I expect the typical
>> "working size" will be much less than 1bn files.
>>
>> My understanding for ldiskfs MDT volume has a ratio of 1 inode per 4096
>> bytes. So ldiskfs MDT volume with 1bn inodes would need a 4TB MDT size.
>> Using DNE, we could have 4 MDS servers, each with a 4TB MDT volume to
>> achieve a filesystem with 4bn inodes.
>>
>> FYI, 4TB volume is a reasonable size when using SSD physical drives (ie.
>> 16TB is not). Any recommendations for reasonable mix of number of DNE
>> MDS + MDT volume size to achieve 4bn files?
>>
>> regards,
>> chris hunter
>> chuntera@gmail.com
>>
>>
>>
>>
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