reasonable xfs fs size for 30-100 TB?

reasonable xfs fs size for 30-100 TB?

[Ralf Gross]

Hi,

we are about to buy some large (at least for us) RAID arrays
(Overland/Xyratex 48x S-SATA). We'll start with ~30 TB and end with
~100 TB. The data will mainly be video data, each file with a size of
2 GB + some meta data. The RAID will be attached by Fibre Channel to
an Debian Etch server with kernel 2.6.18-amd64 and 6 GB RAM (xfsprogs
2.8.11-1).

My main concern is the amount of RAM I need for a fsck of the xfs fs.
Last time I search for the xfs requirements, I found the rule of
thumb: 2 GB RAM for 1 TB of disk storage + some RAM per x inodes.

Last year I deployed one server with a 4 TB xfs fs which is running
absolutely stable since then.

I don't want to creat _one_ big xfs fs, but I also don't want to end
up with 20-30 fs each with 4 TB of size. The question is, what is a
reasonable fs size with 4-6 GB of RAM? Will it be sufficient to add 15
GB of swap for a 10 TB fs? This will slow things certainly down, but
will it work?

Only few clients will access the data on this server. There will be 3
streams of data with ~17MB/s which the server should be able to
provide over GbE. Performance is not the primary goal. There will also
be a backup to tape (ok, _many_ tapes...).

Any thoughts or hints?

Ralf

Re: reasonable xfs fs size for 30-100 TB?

[James Braid]

Ralf Gross wrote:
> My main concern is the amount of RAM I need for a fsck of the xfs fs.
> Last time I search for the xfs requirements, I found the rule of
> thumb: 2 GB RAM for 1 TB of disk storage + some RAM per x inodes.

A real world example: we have a ~70TB filesystem, with ~70M inodes and 
xfs_repair uses about 13-15GB of memory IIRC (haven't run a repair in a 
while) using a recentish 2.8.x version.

Hope that helps.