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Date:	Tue, 14 Dec 2010 21:51:35 +0100
From:	Stephan Boettcher <boettcher@...sik.uni-kiel.de>
To:	<linux-ext4@...r.kernel.org>
Subject: Re: 20TB ext4

Stephan Boettcher <boettcher@...sik.uni-kiel.de> writes:

> Andreas Dilger <adilger@...ger.ca> writes:
>
>> On 2010-12-13, at 09:23, Stephan Boettcher wrote:
>>> A raid1 (/dev/md1) over three 20GB partitions is the root filesystem,
>>> three 20GB partitions for swap, and a RAID5 (/dev/md0) from the six big
>>> partitions.
>>> 
>>> The 10TB /dev/md0 is exported via nbd.  I had to patch nbd-client to
>>> import this on a 32-bit machine, so that part works.
>>> 
>>> The intention was to export two (later three) via nbd to one of the
>>> servers, which combines them to a RAID5² with net capacity 20TB.  With
>>> e2fsprogs master branch I could make a filesystem, but dumpe2fs and
>>> fsck failed.  Mounting the filesystem said: EFBIG.

>> If you have dedicated server nodes, and you want to be able to use
>> these 20TB from multiple clients, you might consider using Lustre,
>> which uses ext4 as the back-end storage, and can scale to many PB
>> filesystems (largest known filesystem is 20PB, from 1344 * 8TB
>> separate ext4 filesystems).
>
> I like thinks to be as simple and transparent as possible :-) The plan
> is to export the fs via NFS.  I will hit the 16 TB limit again, will I?
> I did not test that part yet.  The NFS clients will then probably be
> required to run 64-bit kernels as well.

Excuse me for not knowing all that much about how linux filesystems
work. I was surprised that I could export the 20TB filesystem via NFS
and mount it on a 32-bit (2.6.31) system.  Do I need to expect failures
when I try to actually use it that way, or does the nfs filesystem not
use the page cache or something, so that the 16TB limit does not apply?

Thanks, Stephan


I guess I should upgrade that kernel ...

(root)informatix:/data/hinkelstein# cat /proc/cpuinfo 
processor       : 0
vendor_id       : GenuineIntel
cpu family      : 15
model           : 2
model name      : Intel(R) Pentium(R) 4 CPU 2.00GHz
stepping        : 4
cpu MHz         : 2020.126
cache size      : 512 KB
fdiv_bug        : no
hlt_bug         : no
f00f_bug        : no
coma_bug        : no
fpu             : yes
fpu_exception   : yes
cpuid level     : 2
wp              : yes
flags           : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pebs bts
bogomips        : 4040.25
clflush size    : 64
power management:

(root)informatix:/data/hinkelstein# cat /proc/version 
Linux version 2.6.31 (stephan@...ormatix) (gcc version 4.3.3 (Debian 4.3.3-8) ) #2 Fri Oct 2 08:25:51 CEST 2009

(root)informatix:/data/hinkelstein# df .
Filesystem           1K-blocks      Used Available Use% Mounted on
falbala:/data/hinkelstein/
                     19021934592 651503616 17404166144   4% /data/hinkelstein


-- 
Stephan

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