Comment 2 for bug 1336568

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Mitsuhiro Tanino (mitsuhiro-tanino) wrote :

There are two parameters related to cache.

(1) "write-cache off"
In default setting the write cache is enabled(write-cache on). Therefore I/O is issued via write-back mode
and the I/O is cached on dirty cache.

If we use "write-cache off", Write I/O is issued via write-through mode and the write I/O is not cached.
Read I/O is still cached even where we user this parameter. So read I/O can keep good performance.

(2) "--bsoflags direct"
When we use this parameter, both Read and Write I/O are issued without dirty cache and buffer cache.
Using this parameter, we can suppress increasing buffer cache via tgtd's I/O.

I think these parameters should be used case by case basis.