Feasability of VERY large ext3 file system?

jason andrade jason at dstc.edu.au
Wed Dec 4 06:28:00 CST 2002


On Wed, 4 Dec 2002, Basil Hussain wrote:

> I am soon considering setting up an external RAID array to be attached to
> one of my PowerEdge servers. The RAID array is an external one with it's own
> hardware RAID controller, attached via U160 SCSI. It is likely that this
> array will be at least 1.4 terabytes, possibly up to 2.2 terabytes. I plan
> to run Redhat 8.0 on this server.

You are a brave admin.  We salute you (and unfortunately, will probably laugh
behind your back if it all falls over with much muttering of "we told you so" :-)

I am still conservative and would recommend you consider RH 7.3 (or perhaps
RH 2.1 AS might be a better fit, especially if you also purchase "enterprise"
support to go with that).


> * Would a single multi-TB file system using ext3 be pushing things a bit?

i have seen people demonstrating 1Tbyte ext3 filesystems - i'm sure there are
larger ones out there.  we are also looking at arrays in the 2Tb range but
plan to break it up into 500G chunks for various reasons.  we have a 550G
ext3 filesystem now and so far it has performed well.

a good alternative to ext3 might be XFS instead (though i don't personally
recommend it unless you know what you're doing..) or perhaps reiserfs.

> * The data stored would be organised in a directory hierarchy only one level
> deep. How would ext3 cope with, say, 4000-5000 directories off the file
> system's root?

no issues with that.

> * How much space is lost due to journaling? Basically, given a gigabyte of
> disk, what is the available formatted space?

very little in comparison to the available space.  journal sizes don't
grow (from what i understand) in direct proportion to increased disk.

> If anyone could offer some advice, anecdotes, etc. on running *large* file
> systems using ext3, I would be most grateful.

do you _have_ to have a single filesystem ?  how are you backing it up ?
can everything be down when you need to fsck it and it takes 1-2 hours
to do so ?


regards,

-jason




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