[gpfsug-discuss] Biggest file that will fit inside an inode? What it says!

[Marc A Kaplan]

I just noticed that tsdbfs shows you how much data fits in the inode, even 
if you don't fill it... So a few commands will give you the answer:
dd, sync, ls, tsdbfs, inode 

Encryption uses EAs, so you lose some space in inode to that.
I don't have an encrypted FS handy for testing, if you have one, go ahead 
and use tsdbfs to look at an inode and see whether or not
encryption pushes the data out of the inode, I wouldn't be surprised 
either way.

[root at n2 isizes]# dd if=/dev/urandom bs=1 count=100 of=i100
100+0 records in
100+0 records out
100 bytes (100 B) copied, 0.00226643 s, 44.1 kB/s
[root at n2 isizes]# sync

[root at n2 isizes]# ls -ild i100
16346894 -rw-r--r-- 1 root root 100 Oct  3 09:14 i100
[root at n2 isizes]# tsdbfs mak
Enter command or null to read next sector.  Type ? for help.
inode 16346894
Inode 16346894 [16346894] snap 0 (index 14 in block 255420):
  Inode address: 6:123049072 size 4096 nAddrs 330
  indirectionLevel=INODE status=USERFILE
  objectVersion=1 generation=0x9D45DC1 nlink=1
  owner uid=0 gid=0 mode=0200100644: -rw-r--r--
  blocksize code=5 (32 subblocks)
  lastBlockSubblocks=0
  checksum=0x2496E008 is Valid
  fileSize=100 nFullBlocks=0
    ...
  Data [3968]:
0000000000000000: 17699B6F 5F9ACD28 70C05242 9268F44E  *.i.o_..(p.RB.h.N*
0000000000000010: 8FFCDCC1 C2ACE0EC 69C1FE2A 986B752C  *........i..*.ku,*
0000000000000020: 8E0434E6 1904B7FC 8B0C5709 2243343C  *..4.......W."C4<*
0000000000000030: BD317374 FB5C322D 8E257B69 FF573283  *.1st.\2-.%{i.W2.*
0000000000000040: 515B333B EDFAE930 9B6F8712 0814BF65  *Q[3;...0.o.....e*
0000000000000050: DBDCC25E 87EB2C16 77AE672D 45FB6BE3  *...^..,.w.g-E.k.*
0000000000000060: 65D52D17 00000000 00000000 00000000  *e.-.............*
0000000000000070: 00000000 00000000 00000000 00000000  *................*
 ...
  trailer: is NULL




From:   "Simon Thompson (Research Computing - IT Services)" 
<S.J.Thompson at bham.ac.uk>
To:     gpfsug main discussion list <gpfsug-discuss at spectrumscale.org>
Date:   10/03/2016 12:10 PM
Subject:        Re: [gpfsug-discuss] Biggest file that will fit inside an 
inode?
Sent by:        gpfsug-discuss-bounces at spectrumscale.org




TCT doesn't use dmapi though I thought?
________________________________________
From: gpfsug-discuss-bounces at spectrumscale.org 
[gpfsug-discuss-bounces at spectrumscale.org] on behalf of Luke Raimbach 
[luke.raimbach at googlemail.com]
Sent: 03 October 2016 17:07
To: gpfsug main discussion list
Subject: Re: [gpfsug-discuss] Biggest file that will fit inside an inode?

Surely it wouldn't go? Maybe the data would get copied out rather than 
stubbed... DMAPI can't be stupid enough to stub data out of an inode? Can 
it? Interesting question.

Maybe I'll test that one.

On Mon, 3 Oct 2016 at 17:00 Simon Thompson (Research Computing - IT 
Services) <S.J.Thompson at bham.ac.uk<mailto:S.J.Thompson at bham.ac.uk>> wrote:

Would you tier an in-inode file to the cloud?

I mean, I wouldn't tier an in-inode file out to tape?

Simon
________________________________________
From: gpfsug-discuss-bounces at spectrumscale.org<
mailto:gpfsug-discuss-bounces at spectrumscale.org> 
[gpfsug-discuss-bounces at spectrumscale.org<
mailto:gpfsug-discuss-bounces at spectrumscale.org>] on behalf of Oesterlin, 
Robert [Robert.Oesterlin at nuance.com<mailto:Robert.Oesterlin at nuance.com>]
Sent: 03 October 2016 16:56
To: gpfsug main discussion list
Subject: Re: [gpfsug-discuss] Biggest file that will fit inside an inode?

What's going be taken away if you use Encryption or Transparent Cloud 
Tiering?


Bob Oesterlin
Sr Storage Engineer, Nuance HPC Grid


From: <gpfsug-discuss-bounces at spectrumscale.org<
mailto:gpfsug-discuss-bounces at spectrumscale.org>> on behalf of Marc A 
Kaplan <makaplan at us.ibm.com<mailto:makaplan at us.ibm.com>>
Reply-To: gpfsug main discussion list <gpfsug-discuss at spectrumscale.org<
mailto:gpfsug-discuss at spectrumscale.org>>
Date: Monday, October 3, 2016 at 10:46 AM
To: gpfsug main discussion list <gpfsug-discuss at spectrumscale.org<
mailto:gpfsug-discuss at spectrumscale.org>>
Subject: [EXTERNAL] Re: [gpfsug-discuss] Biggest file that will fit inside 
an inode? 3968!!

On a non-SELINUX system the answer is 3968 of data in a 4K inode, just 128 
bytes of metadata.

Caution: it's possible in some future release, this could change ... I 
don't know of any plans, I'm just saying ...

Inode 16346892 [16346892] snap 0 (index 12 in block 255420):
  Inode address: 6:123049056 size 4096 nAddrs 330
  indirectionLevel=INODE status=USERFILE
  objectVersion=1 generation=0xC0156CB nlink=1
  owner uid=0 gid=0 mode=0200100644: -rw-r--r--
  blocksize code=5 (32 subblocks)
  lastBlockSubblocks=0
  checksum=0xAD8E0B4B is Valid
  fileSize=3968 nFullBlocks=0
  currentMetadataReplicas=1 maxMetadataReplicas=2
  currentDataReplicas=1 maxDataReplicas=2
  ...
  Data [3968]:
0000000000000000: BCA91252 2B64BEDC A7D7BA9D D5BE8C30  *...R+d.........0*
...
0000000000000F70: DA925E2F 16A68C01 03CA5E37 08D72B7F  *..^/......^7..+.*
  trailer: is NULL


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