[KLUG Members] ext3 size limits

[John Pesce]

On 3 Oct 2002, Adam Williams wrote:

> >Would I have a problem using a 1TB external SCSI RAID array under Linux 
> >with an EXT3 filesystem?
> 
> With 2.4.x you have a maximum *FILE* size of ~16 terabytes.  
> 
> Maximum *FILESYSTEM* size with ext2/3 without tweaking anything is ~4
> terabytes.  This assumes a 4k block size, and on Intel 32-bit I think
> you are limited to page size no larger than PAGE_CACHE_SIZE, which is 4k
> on most processors.  Still, your 1TB is well within the 4TB limit.
> 
> *BUT* what are you going to be storing in this filesystem?  If it is

Well, We have a 590GB drive now. There are two major data streams we 
archive and process. One are weather products from NOAA( Aviation weather, 
radar images, satellite images), which range in size from 100K to 10s of 
Megs on the order of 5G per day. 
The second stream is ASDI data from the air traffic control NAS computers 
on the order of a 400M file each day.
We also do extensive post processing of this data to produce files on the 
order of 120M. 
In theory I could make a couple partitions, one for the larger ASDI files 
and one for the smaller weather data. I was hoping to not have to draw the 
line on how much to allocate to each.

Does this help paint a picture? Can someone please help make some tough 
decisions to plan this. I've never worked with partitions this large 
before and I would hate to fill the filesystem before the drive is full.
How many inodes should I figure for this size? 1 for every 50M??

I have other concerns about backups and fragmentation. The current thread 
on defrag is a bit worrisome at the moment. If this filesystem is going to 
get slower with time and would be extremely difficult to do a full backup 
and format then there are greater issues. I was hoping to choose a highly
redundant and fault tolerant media since the data is so volatile it is 
difficult to backup.

> Do you have a separate physical volume (or partition on the RAID device)
> for the journal?

Good point. I just created a journel on the existing 590G RAID and mounted 
it ext3, it was ext2. This seemed like a good option since the new RH7.3 
system I moved it to had ext3 partitions. It takes 45 minutes to fsck it!

I haven't had a chance to read up on journeling yet. I assume from the 
name that any writes to the filesystem are journeled and committed 5 
seconds later. This, I believe, would allow the writes to occur when the 
journel is recovered upon reboot if the system crashed. Which brings me to 
the the new system, for some reason It kernel paniced a few time lately. 
When RH 7.3 reboots it give the option to do a filesystem check. 
If I don't say yes, it recovers the journel and goes on. Is this safe? 
Should I still filesystem check after ever unclean boot?

Thanks everyone