On 2014/9/16 4:25, Brassow Jonathan wrote:
On Sep 14, 2014, at 9:24 PM, Romu Hu wrote:
Hi,
According to https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/6-Beta/html-single/6.6_Release_Notes/index.html#bh-storage, dm-cache and dm-era have been added into RHEL6.6 as technology preview, but I couldn't find any other documentation about using dm-cache and dm-era. I found the following utilities in
/usr/sbin/era_check
/usr/sbin/era_dump
/usr/sbin/era_invalidate
/usr/sbin/cache_check
/usr/sbin/cache_dump
/usr/sbin/cache_repair
/usr/sbin/cache_restore
I guess these utilities are related to dm-era and dm-cache, respectively. There are only manpages for the cache utilities. After reading the manpages I still have no clue how to use these technologies. I want to do a sanity check of these technologies on my SAN storage. Is it possible to try dm-cache and dm-era without a SSD? e.g. using ram to imitate a fast block device..
Any idea?
You can use cache to teir any block device over another. Layering faster, smaller drives over slower, larger ones is the point; but for testing non-performance things you can still do it. For the cache target, it would be a more inclusive test to go through LVM. The lvmcache.7 man page would help out with that. There is no dm-era support in LVM ATM.
brassow
Thanks, I have successfully set up LVM caching with dm-cache, works like
a charm. However, I still haven't any useful documentation about how to
set dm-era. Any idea?
Thanks
Romu
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