Pinned topic Can gpfs inode be increased online (without re-mounting?)
Re: Can gpfs inode be increased online (without re-mounting?)2010-07-21T09:29:03ZThis is the accepted answer. This is the accepted answer.
- dlmcnabb 120000P4JT
Can you give me a example for below formula
maximum number of files = (total file system space/2) / (inode size + subblock size)
1. total file system space = is this from df -k?
2. inode size = is this from mmlsfs?
3. subblock size = How to get subblock size?
Re: Can gpfs inode be increased online (without re-mounting?)2010-07-21T20:20:44ZThis is the accepted answer. This is the accepted answer.
- SystemAdmin 110000D4XK
The inode size is almost always 512 bytes: mmlsfs $fsname -i
One subblock is always 1/32 of a fullblock: mmlsfs $fsname -B, or redundantly the fragment size: mmlsfs $fsname -f.
You should consider what your average file size and number of entries per directory might be.
But you can always add more disks and increase the number of inodes later.
sabujp 270006F8J512 Posts
Re: Can gpfs inode be increased online (without re-mounting?)2013-09-27T12:33:47ZThis is the accepted answer. This is the accepted answer.
- dlmcnabb 120000P4JT
mr mcnabb (or anyone else that knows for sure),
You mention "you need enough space for at least one subblock per file", so I'm assuming that means that I can only store 1 inode per metadata subblock and the rest of the subblock is used to store the data contents of the file should it fit in (subblock - inode) bytes? Does this occur for dataAndMetadata pools only or also for metadata only pools?
I was confused since I ran "mmfsadm dump fs | grep -i inodes" and saw in this section :
bgd_NeedFullScan 0 bgd_FullScanStarted 0 bgd_PreviousInodeScanIno -1inodes: size 512 (1 sectors), inodes per block 512, disk addrs 32
Since my metadata block size is 256K, the above says i can get 512 inodes in a block. So which is true, 1 inode per subblock or as many inodes will fit into the blocksize depending on what I've set inode size to?
Also, is there any performance benefit to increasing the inode size from 512 bytes? With my testing on RAID1 configured SSD's, I saw no performance difference with metadata operations, e.g. rm's, ls's and small file creation, using various metadata block sizes (16k - 16M) and varying inode sizes (512, 1024, or 4096) within those metadata block sizes.
ThanksUpdated on 2013-09-27T12:35:21Z at 2013-09-27T12:35:21Z by sabujp
Re: Can gpfs inode be increased online (without re-mounting?)2013-09-27T17:07:14ZThis is the accepted answer. This is the accepted answer.
- sabujp 270006F8J5
The "one inode + one subblock" is just an extremely rough estimate of the maximum number of files that would fit on your existing disks. It does not say anything about how those are allocated. The "inode 0" file in GPFS is the file of all the inodes. It is allocated in blocksize chunks and each block is filled with inodes of whatever the configured inode size is. Then the calculation assumes that if you created a small file using each inode, they might each use at least one subblock. It is just trying t determin a theoretical limit on the number of inodes.
The calculation does not even look at whether there are separate data and metadata disks. Disk usage can be changed using mmchdisk.
As of release 3.5 this calculation is even more vague, since GPFS will store file/directory/symlink data inside the inode itself if the file is small enough. It may not even need a subblock. Most small directories will fall into this category. An inode has a small fixed header of roughly 128 bytes. The rest of the inode can be used for a mixture of disk block addresses, Extended Attributes, and/or data.
You can create filesystem with larger inodes, and thus store more small files directly in the inode. This can make reading these small files much more efficient since the data read is free after reading the inode.