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Tux12Fun Apprentice
Joined: 16 Aug 2007 Posts: 156
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Posted: Wed Aug 15, 2012 12:14 pm Post subject: [solved] Playing with mdadm |
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Hello,
I build the following setup, only for playing, but i haven't expected that this would be so slow.
Does anybody know how its so slow.
Setup:
DISK1 (USB - HDD)
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= f1, f2, f3, f4, f5, f6, f7, f8, f9, f10 =
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DISK2 (USB - HDD)
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= f11, f12, f13, f14, f15, f16, f17, f18, f19, f20 =
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Every File (f1-f20) is bound to one loop device (loop1-20)
now i build my raid (only for space/none security) like this. (Files have different size so i use linear)
mdadm --build --auto=part --verbose /dev/md0 --level linear -c 2048 -n 20 /dev/loop1 /dev/loop11 /dev/loop2 /dev/loop12 /dev/loop3 /dev/loop13 ...
Now I expected to write with the throughput of at least one disk (26mb/s) but if i write with dd i get only 6mb/s. Writing to a loop device is working with about 23mb/s
Last edited by Tux12Fun on Wed Aug 15, 2012 11:26 pm; edited 1 time in total |
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eccerr0r Watchman
Joined: 01 Jul 2004 Posts: 9645 Location: almost Mile High in the USA
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Posted: Wed Aug 15, 2012 4:08 pm Post subject: |
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What are you trying to do here?
There are multiple layers of filesystem munging translation here, that's one possible reason; also the possibility of fragmentation hurts this... _________________ Intel Core i7 2700K/Radeon R7 250/24GB DDR3/256GB SSD
What am I supposed watching? |
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NeddySeagoon Administrator
Joined: 05 Jul 2003 Posts: 54096 Location: 56N 3W
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Posted: Wed Aug 15, 2012 4:55 pm Post subject: |
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Tux12Fun,
... and all this fun on USB, where there is no DMA for HDDs.
If you want to play with mdadm on USB, use real partitions and non journalling filesystems. _________________ Regards,
NeddySeagoon
Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail. |
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