[Lustre-discuss] inode tuning on shared mdt/mgs

[Kevin Van Maren]

Andreas Dilger wrote:
> On 2011-07-01, at 12:03 PM, Aaron Everett <aeverett at forteds.com 
> <mailto:aeverett at forteds.com>> wrote:
>> I'm trying to increase the number of inodes available on our shared 
>> mdt/mgs. I've tried reformatting using the following:
>>
>>  mkfs.lustre --fsname fdfs --mdt --mgs --mkfsoptions="-i 2048" 
>> --reformat /dev/sdb
>>
>> The number of inodes actually decreased when I specified -i 2048 vs. 
>> leaving the number at default. 
>
> This os a bit of an anomaly in how 1.8 reports the inode count. You 
> actually do have more inodes on the MDS, but because the MDS might 
> need to use an external block to store the striping layout, it limits 
> the returned inode count to the worst case usage. As the filesystem 
> fills and these external blck

[trying to complete his sentence:]
are not used, the free inode count keeps reporting the same number of 
free inodes, as the number of used inodes goes up.

It is pretty weird, but it was doing the same thing in v1.6

>> We have a large number of smaller files, and we're nearing our inode 
>> limit on our mdt/mgs. I'm trying to find a solution before simply 
>> expanding the RAID on the server. Since there is plenty of disk 
>> space, changing the bytes per inode seemed like a simple solution. 
>>
>> From the docs:
>>
>> Alternately, if you are specifying an absolute number of inodes, use 
>> the-N <number of inodes> option. You should not specify the -i option 
>> with an inode ratio below one inode per 1024 bytes in order to avoid 
>> unintentional mistakes. Instead, use the -N option.
>>
>> What is the format of the -N flag, and how should I calculate the 
>> number to use? Thanks for your help!
>>
>> Aaron