Hi Andrew,
On Wednesday 19 September 2007 09:55:14 am Lundgren, Andrew
wrote:> I am trying to determine sizing and layout for the MDS, MDT and OST
> partitions.
>
> From what I can tell from the documentation, the MDS only hold
> configuration information. Is that correct?
The MGS (Management Server) holds the configuration part. The MDS
(Metadata Server) is the the server which hosts the MDT(s) (Metadata
target(s)) which actually store the metadata information for a
filesystem. In the documentation, MDS often refers to both MDS and
MDT, which is sometimes confusing.
See the Lustre Manual (Lustre Components) [1] for more details.
> The documentation mentions that I should have about 4k/file in the
> MDT, how much do I need in the MDS?
The MDS per se is not a device, that''s just the name of the server to
which the MDT device is connected. You can also colocate the MGS and
the MDT in the same device.
> For a 2.5 TB cluster with 4 OSTs, 1 MDS, and 1 MDT is there going to
> be much of anything in an MDS if all it holds is configuration
> information?
All you need to dimension is the MDT device. The Lustre Manual [2] gives
some information on that topic. Its size will depend of the average size
of your files. For an average size of 5MB, your 2.5TB will require
2.5 10^12 / 5 10^6/inode = 0.5 10^6 inodes. With the default size of 4KB
per inode, it''s about 2GB. CFS recommends to use at least twice that
number, ie. 4GB, and if you have available space, double it again
and you should be safe. :)
[1]
http://manual.lustre.org/manual/LustreManual16_HTML/DynamicHTML-01-1.html#wp1028408
[2]
http://manual.lustre.org/manual/LustreManual16_HTML/DynamicHTML-18-1.html#wp1046815
Cheers,
--
Kilian