[gpfsug-discuss] default inode size

[GORECKI, DIETER]

Lukas,

One other thing to consider is the storage of data inside the inode itself for very small files. GPFS has the ability to use the remaining [kilo]bytes of the inode to store the data of the file whenever the file is small enough to fit in.

Anyone correct me if I am wrong, but with 4k inodes, you can store up to (4096-128 header) 3968 bytes of data. (without ILM)

So regarding the size of the files you intend to store into your filesystem, it might be very interesting to take advantage of the performance of your SSD's to store small files.

Regards,

Dieter

-----Original Message-----
From: gpfsug-discuss-bounces at spectrumscale.org [mailto:gpfsug-discuss-bounces at spectrumscale.org] On Behalf Of Lukas Hejtmanek
Sent: Wednesday, March 15, 2017 1:37 PM
To: gpfsug main discussion list
Subject: Re: [gpfsug-discuss] default inode size

On Wed, Mar 15, 2017 at 08:22:22AM -0400, Stephen Ulmer wrote:
> You need 4K nodes to store encryption keys. You can also put other useful things in there, like extended attributes and (possibly) the entire file.
> 
> Are you worried about wasting space?

well, I have 1PB of capacity for data disks and 3TB of capacity for metadata (SSD).

With 512B inodes, this ration seemed to be quite ok, while with 4k inodes, I run out of free space on SSD pretty fast. So I'm thinking about re-creating file system with smaller inode size.

I don't think I will ever need encryption keys.

--
Lukáš Hejtmánek
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