geom stripe perfomance question
Oles Hnatkevych
don_oles at able.com.ua
Sat Nov 4 20:29:02 UTC 2006
Hello all!
I wonder why geom stripe works much worse than the separate disks that
constitute stripe.
I have a stripe from two disks. Disks are on separate ATA channels.
root# gstripe list
Geom name: bigdata
State: UP
Status: Total=2, Online=2
Type: AUTOMATIC
Stripesize: 262144
ID: 4233231544
Providers:
1. Name: stripe/bigdata
Mediasize: 500118323200 (466G)
Sectorsize: 512
Mode: r1w1e1
Consumers:
1. Name: ad1
Mediasize: 250059350016 (233G)
Sectorsize: 512
Mode: r1w1e2
Number: 0
2. Name: ad2
Mediasize: 250059350016 (233G)
Sectorsize: 512
Mode: r1w1e2
Number: 1
Now let's read one of them and stripe.
root# dd if=/dev/ad1 of=/dev/null bs=1m count=1000
1000+0 records in
1000+0 records out
1048576000 bytes transferred in 14.579483 secs (71921343 bytes/sec)
root# dd if=/dev/stripe/bigdata of=/dev/null bs=1m count=1000
1000+0 records in
1000+0 records out
1048576000 bytes transferred in 15.882796 secs (66019610 bytes/sec)
What I would expect is doubling the speed of transfer, not
slowing down. Am I wrong? Or is geom_stripe inefficient?
I am running 6.2-PRERELEASE on Celeron 800.
--
Oles Hnatkevych mailto:don_oles at able.com.ua
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