(LONG) Delay when writing to ext4 LVM after boot

[Ken Bass]

(I previously asked this question in the LVM list, and they suggested I ask
here.)

I have a large LV, about 6.5T, consisting of 4 physical drives of various
sizes. The LV is formatted as ext4. There is no raid  involved (hardware of
software).

After I first boot, if I try to write a large file (>~ 80M) to this LV, the
write hangs for about 1minute or more, then continues on at full speed and
finishes successfully. Writes of small files don't show this delay. After
that first write and delay, all subsequent writes to other large files
proceed at full speed.

I am currently running Fedora 17 64bit  (kernel 3.8.4-102.fc17.x86_64) but
have noticed this also in previous systems (both 64 and 32bit). With
smaller file systems ( < 1T ), there was a delay, but it was small, and it
increased significantly as I increased the LV size.

I have run e2fsck with the -D option (before attempting a write), which
made no difference. Also, fwiw,  I am mounting this with the default
options. I've tried other options that were suggested to tweak ext4, but,
again, no effect. This LV is also not my system (root) partition - that is
on a separate physical drive.

Any ideas? Suggestions?

(I will gladly supply additional info as requested.)

TIA

ken
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