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stec-inc / EnhanceIO

EnhanceIO Open Source for Linux
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adding cache in either wt or ro mode greatly reduces read performance #97

Closed andenix closed 9 years ago

andenix commented 9 years ago

When I add eio_cli create -d /dev/sda3 -s /dev/sdc -c my_first_enhanceio

where sdc is my SSD drive and sda3 my /home

My read speed drops by a factor of 10-15x I tried removing the cache while copying the file and read speed gets to normal.

Using 4.0.4 kernel on Debian 64

EhcnceIO compiled from git.

andenix commented 9 years ago

I didn't try wb mode because write speed of my SSD is low.

onlyjob commented 9 years ago

IMHO your problem is because all reads from cached device are also written to caching device. Therefore with cache attached you will not be able to read faster than your SSD can write. As far as I'm aware this is a typical problem with EnhanceIO, flashcache, bcache and dm-cache (but not with dm-writeboost because the latter is not focused on caching reads).

Besides on Debian it might be better (and easier) to use official package.

andenix commented 9 years ago

I never thanked you for the insights and probable ways of resolution. Thank you.

onlyjob commented 9 years ago

I'm glad if my information was useful to you. :)