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Abood Nasr
Abood Nasr

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Slow I/O simulation in linux

  1. Create place to store our data. 
dd if=/dev/zero of=/tmp/delayed-block bs=1G count=1
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OUTPUT

1+0 records in
1+0 records out
1073741824 bytes (1,1 GB, 1,0 GiB) copied, 5,24011 s, 205 MB/s
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  1. Create a loop device 
losetup --find --show /tmp/delayed-block
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OUTPUT

/dev/loop5
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  1. Create a delayed mapper using dm-delay 
echo "0 `blockdev --getsz /dev/loop0` delay /dev/loop5 0 <milliseconds> | dmsetup create delayed-device"
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  1. Format and mount the delayed device to folder 
mkfs.ext4 /dev/mapper/delayed-device
mkdir ~/delayed-folder
mount -o sync /dev/mapper/delayed-device ~/delayed-folder
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we must select sync option to prevent kernel enhancements.

Top comments (1)

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fatuglynoobtroll profile image
NoobPhat •

The dmsetup mapper command didn't work for me; guessing the pipe messes it up. Here is my version:
sudo dmsetup create delayed-device --table "0 $(sudo blockdev --getsz /dev/loop1) delay /dev/loop1 0 100"