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Re: EXT3 with 2.2.20 - Is it stable enough for a production server th at is used 24X7?



On Sun, Nov 18, 2001 at 07:36:34PM +0100, Giulio Orsero wrote:
> 
> Is this number global or relative to each ext3 fs?

The number is global, but the limit is enforced on a per-filesystem.
Arguably I should have made the patch account for the number of pinned
transactions globally, but I didn't.  (I was in a hurry when I did the
patch since a paying customer were complaining and we needed a
solution quickly.  Customers can be such cry-babies sometimes.  :-)

> What would be a safe value for a system with 4MB journal and 4 or 8 ext3 fs,
> with say 64MB or 128MB system memory?

It's hard to say; it really depends on your workload and how many ext3
filesystems you have.

If you turn on the debugging sysctl, you'll be able to see when the
throttling is getting triggered.  So if you set it too high, then
you'll be able to see that it's not having any effect (also, under
extreme loads the system will start exhibit extreme memory pressure
symptoms).  So once you find that point, start dropping the limit
until the system seems to perform acceptably under high filesystem
write loads.

The "keep increasing the limit until the system wedges and then back
it off a quarter turn" probably wasn't the convenient answer you were
looking for; sorry!

							- Ted





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