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Is there is are some way to setup local replication of the one disk to the another ( Ubuntu ) in the such way that all read operations will be involve only first disk ? Such configuration will be very usefull for AWS SSD instances. In this case SSD instance storage ( which is non-persistent disk and will be erased after instance stopped ) can be replicated to the EBS disk. When using such configuration data intensive services ( like MySQL or MongoDB ) can be configured to use SSD disk and in the same time we can ensure that data will be permanently stored in the EBS.

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You can try to create md device in RAID1 mode where the read operations are issued to the faster device preferably

mdadm --create --verbose /dev/md0 --level=mirror --raid-devices=2 --write-mostly /dev/sdb1 /dev/sdc1

where the device /dev/sdb is slower for reading (e.g. SATA drive) while the /dev/sdc is performing better (e.g. SSD drive). The configuration above means the drive /dev/sdc will be avoided for reading.

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What you are looking for is called bcache: http://bcache.evilpiepirate.org/

It writes and reads from the faster device, while periodically writing to the slower one

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this might help you: dd if=/dev/sda of=/dev/sdb

dd command can copy disk in raw format. It will copy partition table and bootloader and all partitions within this disk.

if=/dev/sda : Input disk (source)

of=/dev/sdb : Output disk (destination)

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  • You should at least tell him what does that do
    – miniBill
    Feb 15, 2014 at 23:06

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