<div dir="ltr"><div><div>Another thing to consider is how many disk block pointers you have room for in the inode, and when you'll need to add additional indirect blocks. Ref: <a href="http://files.gpfsug.org/presentations/2016/south-bank/D2_P2_A_spectrum_scale_metadata_dark_V2a.pdf" target="_blank">http://files.gpfsug.org/<wbr>presentations/2016/south-bank/<wbr>D2_P2_A_spectrum_scale_<wbr>metadata_dark_V2a.pdf</a><br><br></div>If I understand that presentation correctly.. a block pointer is 12 bytes, so a 1 KB inode can hold approximately 70 block pointers -- ie. any file larger than 70 blocks will need additional indirect blocks to hold the addresses, requiring minimum one additional sub-block. With a 1 MB blocksize filesystem (data and metadata), files between 75 MB and 3 GB will need 1x inode and 1x indirect block = 1 KB + 32 KB metadata space. If your files are smaller than 75 MB, the address pointers fit in the 1K inode.<br><br></div>If you have 4 KB inode, files smaller than 340 MB will fit all pointers in the inode.<br><div><br></div><div><br></div><div> -jf<br></div><div><br></div></div><div class="gmail_extra"><br><div class="gmail_quote">On Wed, Mar 15, 2017 at 2:26 PM, Lukas Hejtmanek <span dir="ltr"><<a href="mailto:xhejtman@ics.muni.cz" target="_blank">xhejtman@ics.muni.cz</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><span class="">On Wed, Mar 15, 2017 at 01:12:44PM +0000, GORECKI, DIETER wrote:<br>
> 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.<br>
><br>
> 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)<br>
><br>
> 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.<br>
<br>
</span>I agree it would, however, I have 30 % free capacity on SSDs only right now (with<br>
some snapshots and ~70M files). So I'm afraid I have to either change the<br>
rotational disks to hold metadata as well or do not create more<br>
files/snapshots or decrease the inode size. I cannot add more SSDs as I do not<br>
have free disk slots in HW.<br>
<div class="HOEnZb"><div class="h5"><br>
--<br>
Luká\u0161 Hejtmánek<br>
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