05-31-2012 01:27 PM
We have 40 TB VXFS 4 way Striped File System (40 Luns, 10 Luns in each column) and we observed that during writes only one lun each column. Since this is a striped file system we are expecting all Luns will be hit when we perform the operations on the file systems. Wondering what is the reason for this behavior.
05-31-2012 01:37 PM
This is expected behaviour as column dictates how many LUNs are written, so sounds like you have 4 columns (10 in each column) which you can confirm by a "vxprint -th" where you should see something like 4/128 for the plexes (128 is stripe width, but it may be something different like 256). If you want to write to all LUNs, then you need to have a column of 40, but I would not recommend this. Beyond a column of about 10 I think, performance does not get any better, perhaps even worse. Also if you extend volume at a later stage you have to add a mulitple of LUNs of the column, so at the moment you could add a multiple of 4 LUNs, so if you changed column to 40, you would have to add 40 LUNs if you wanted to extend volume.
Mike
05-31-2012 01:48 PM
Mike,
Thanks for the response. What if, we create a separate column for each lun means 40 columns for 40 luns - with this we can add one lun at a time for expansion? Any performance issues with this setup as well?
Thanks
Rajesh
05-31-2012 01:52 PM
If you have 40 collumns, then you will need to add a multiple of 40 LUNs when you expand and a column size of that big is likely to be non-optimal.
Mike