how to improve qcow performance?

[Geraldo Netto]

Dear Friends,

I beg your pardon for such a newbie question
But I would like to better understand how to improve the qcow performance

I was checking the qemu-img and it seems that the following parameters
are the most relevant to optimise the performance, no?

  'cache' is the cache mode used to write the output disk image, the valid
    options are: 'none', 'writeback' (default, except for convert),
'writethrough',
    'directsync' and 'unsafe' (default for convert)

Should I infer that directsync means bypass all the stack and write
directly to the disk?

  'src_cache' is the cache mode used to read input disk images, the valid
    options are the same as for the 'cache' option

I didn`t follow where should I look to check the 'cache' options :`(

I guess that using smaller files is more performance due to the
reduced number of metadata to handle?
In any case, I saw the qemu-io command and I plan to stress test it


Thank you very much/Kind Regards,

Geraldo Netto
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