Date: Wed, 6 Apr 2022 23:19:22 +0200
From: Jan Bramkamp <crest@rlwinm.de>
To: performance@freebsd.org
Subject: Re: {* 05.00 *}Re: Desperate with 870 QVO and ZFS
Message-ID: <d5e51e47-d24a-27bd-ac56-295bfa798de7@rlwinm.de>
In-Reply-To: <d8eec440-aff5-e2c7-35d5-04ac96939213@sentex.net>
References: <4e98275152e23141eae40dbe7ba5571f@ramattack.net> <665236B1-8F61-4B0E-BD9B-7B501B8BD617@ultra-secure.de> <0ef282aee34b441f1991334e2edbcaec@ramattack.net> <28e11d7ec0ac5dbea45f9f271fc28f06@ramattack.net> <ca3f86f2-94a1-be94-ad55-7bd1c9bc50ab@grosbein.net> <7aa95cb4bf1fd38b3fce93bc26826042@ramattack.net> <alpine.GSO.2.20.2204061513180.9475@scrappy.simplesystems.org> <d8eec440-aff5-e2c7-35d5-04ac96939213@sentex.net>
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On 06.04.22 22:43, mike tancsa wrote:
> On 4/6/2022 4:18 PM, Bob Friesenhahn wrote:
>> On Wed, 6 Apr 2022, egoitz@ramattack.net wrote:
>>>>
>>>> WE DON'T USE COMPRESSION AS IT'S NOT SET BY DEFAULT. SOME PEOPLE
>>>> SAY YOU SHOULD HAVE IT ENABLED.... BUT.... JUST FOR AVOID HAVING
>>>> SOME DATA COMPRESSED SOME OTHER NOT (IN CASE YOU ENABLE AND LATER
>>>> DISABLE) AND FINALLY FOR AVOID ACCESSING TO INFORMATION WITH
>>>> DIFFERENT CPU COSTS OF HANDLING... WE HAVE NOT TOUCHED COMPRESSION....
>>
>> There seems to be a problem with your caps-lock key.
>>
>> Since it seems that you said that you are using maildir for your mail
>> server, it is likely very useful if you do enable even rather mild
>> compression (e.g. lz4) since this will reduce the write work-load and
>> even short files will be stored more efficiently.
>>
> FYI, a couple of our big zfs mailspools sees a 1.24x and 1.23x
> compress ratio with lz4. We use Maildir format as well. They are not
> RELENG_13 so not sure how zstd would fair.
I've found that Dovecot's mdbox format compresses a lot better than
Maildir (or sdbox), because it stores multiple messages per file
resulting in files large enough to contain enough exploitable reduncancy
to compress down to the next smaller blocksize. In a corporate or
education environment where users tend to send the same medium to large
attachments multiple times to multiple recipients on the same server
Dovecot's single instance storage is a game changer. It reduced my IMAP
storage requirements by a *factor* of 4.7 which allowed me to get rid of
spinning disks for the mail servers instead of playing losing games with
hybrid storage. Dovecot also supports zlib compression in the
application instead of punting it to the file system. I don't know if
Cyrus IMAP offers similar features, but if it does I would recommend
evaluating them instead of compressing or deduplicating at the file
system level.
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<div class="moz-cite-prefix">On 06.04.22 22:43, mike tancsa wrote:<br>
</div>
<blockquote type="cite"
cite="mid:d8eec440-aff5-e2c7-35d5-04ac96939213@sentex.net">On
4/6/2022 4:18 PM, Bob Friesenhahn wrote:
<br>
<blockquote type="cite">On Wed, 6 Apr 2022, <a class="moz-txt-link-abbreviated" href="mailto:egoitz@ramattack.net">egoitz@ramattack.net</a>
wrote:
<br>
<blockquote type="cite">
<blockquote type="cite">
<br>
WE DON'T USE COMPRESSION AS IT'S NOT SET BY DEFAULT. SOME
PEOPLE SAY YOU SHOULD HAVE IT ENABLED.... BUT.... JUST FOR
AVOID HAVING SOME DATA COMPRESSED SOME OTHER NOT (IN CASE
YOU ENABLE AND LATER DISABLE) AND FINALLY FOR AVOID
ACCESSING TO INFORMATION WITH DIFFERENT CPU COSTS OF
HANDLING... WE HAVE NOT TOUCHED COMPRESSION....
<br>
</blockquote>
</blockquote>
<br>
There seems to be a problem with your caps-lock key.
<br>
<br>
Since it seems that you said that you are using maildir for your
mail server, it is likely very useful if you do enable even
rather mild compression (e.g. lz4) since this will reduce the
write work-load and even short files will be stored more
efficiently.
<br>
<br>
</blockquote>
FYI, a couple of our big zfs mailspools sees a 1.24x and 1.23x
compress ratio with lz4. We use Maildir format as well. They are
not RELENG_13 so not sure how zstd would fair.
<br>
</blockquote>
I've found that Dovecot's mdbox format compresses a lot better than
Maildir (or sdbox), because it stores multiple messages per file
resulting in files large enough to contain enough exploitable
reduncancy to compress down to the next smaller blocksize. In a
corporate or education environment where users tend to send the same
medium to large attachments multiple times to multiple recipients on
the same server Dovecot's single instance storage is a game changer.
It reduced my IMAP storage requirements by a <b>factor</b> of 4.7
which allowed me to get rid of spinning disks for the mail servers
instead of playing losing games with hybrid storage. Dovecot also
supports zlib compression in the application instead of punting it
to the file system. I don't know if Cyrus IMAP offers similar
features, but if it does I would recommend evaluating them instead
of compressing or deduplicating at the file system level.<br>
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