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Re: qcow2 overlay performance
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From: |
Alberto Garcia |
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Subject: |
Re: qcow2 overlay performance |
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Date: |
Wed, 26 Aug 2020 20:00:26 +0200 |
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User-agent: |
Notmuch/0.18.2 (http://notmuchmail.org) Emacs/24.4.1 (i586-pc-linux-gnu) |
On Wed 26 Aug 2020 03:18:32 PM CEST, Kevin Wolf wrote:
>> My understanding is that writing 4K blocks requires a
>> read-modify-write because you must fetch a complete cluster from
>> deeper in the overlay chain before writing to the active
>> overlay. However, this does not explain the drop in performance when
>> writing 64K blocks.
Your understanding is correct. Apart from what Kevin wrote, I assume
that the write requests are always aligned to the cluster size, is that
right?
Berto