xfs preallocation timeout

[Michael Monnerie]

Does /proc/sys/vm/dirty_expire_centisecs influence the maximum time XFS 
takes before the "in-memory but not on disk" preallocation actually 
starts writing to disk? If not, which parameter does influence how long 
files are grouped together in memory before writing them really to disk? 
The longer the better for performance, but more risk for data loss of 
course. 

I ask this because I want to know when copying files over the net to an 
XFS drive, how I can prevent fragmentation to occur. Example: If a 
packet of 1024 Bytes arrives every 1/100th second, it needs 0.64s to get 
64KB of data, 1.28s to get 128KB. If the prealloc timeout is one second, 
it's effectively not used in this case. So if you got a server where you 
know files arrive at a certain speed, fine tuning this prealloc timeout 
could help prevent fragmentation.

mfg zmi
-- 
// Michael Monnerie, Ing.BSc    -----      http://it-management.at
// Tel: 0660 / 415 65 31                      .network.your.ideas.
// PGP Key:         "curl -s http://zmi.at/zmi.asc | gpg --import"
// Fingerprint: AC19 F9D5 36ED CD8A EF38  500E CE14 91F7 1C12 09B4
// Keyserver: wwwkeys.eu.pgp.net                  Key-ID: 1C1209B4