On Jun 12, 2008, at 3:21 PM, Kirk Strauser wrote:
Does gstripe read an entire stripe at a time? If so, why do that
instead of
just reading a few requested blocks? If not, then is there any
advantage
to large stripes?
Apparently it won't read anything larger than your stripe size which
defaults to a miserable 4k.
Doesn't appear the driver collects multiple pending reads and merges
them into one transaction. Don't know if ATA/SATA allows that or not,
believe it was called "scatter/gather" in SCSI.
Built a gstripe volume a while back and played with various stripe
sizes trying to maximize KB/t as shown in "systat -v" during massive
file read/writes. A stripe size of 131072 (128k bytes) was the best I
could get at about 43 KB/t. About 25 MB/sec each on two drives that
are capable of 4x that on a Mac Pro (about 55 MB/sec single drive on
inner tracks to 100 MB/sec on outer, reading with md5).
Anyway, throughput was terrible with the default 4k stripe.
If there is a tuning knob that I have missed, would appreciate being
told what.
IIRC vinum's default stripe was about 87.5kB and "systat -v" reported
transactions of that size.
--
David Kelly N4HHE, [EMAIL PROTECTED]
========================================================================
Whom computers would destroy, they must first drive mad.
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