SSDs, backups and Maibox vs Maildir

maquinadigital

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Aug 10, 2006
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We're now using Mailbox on our servers (some legacy accounts we didn't migrate as POP3 got confused on conversion and a lot of clients complained of having the messages downloaded again).
This was almost mandatory as backups kept getting slower and slower and converting to mbox allowed for a lot of time saving on that.

Now we're starting to use SSDs and I'm considering going backup to maildir. Of course backups will get slower as we have hdd on the nas side but I'm hoping it will fall in between the current status and an optimal status.
I'm considering this in hope of SSD write reduction. I believe the mbox file rotation (in a 10MB file, if a message of 10KB is deleted, dovecot rewrites de entire file without the message) can take a toll on SSD TBW and using maildir will allow that writes saving, as maildir only deletes / writes what it needs and indexes (and mailbox also has indexes).

Does anyone has experience in this backup SSDs with maildir? Is it a lot slower than mbox? And what's your opinion on SSD usage on mailbox vs maildir? I have a point or am I being too picky?

Best regards
Daniel
 

cPJustinD

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Jan 12, 2021
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Hello maquinadigital! The mdbox format stores multiple messages in a file and uses a simpler indexing scheme. This format requires fewer files, reduces inode usage significantly, and decreases disk space usage. With that being said, running backups on an SSD with mdbox will likely be much faster than a server using maildir.

All in all, SSD with mdbox seems to be the better option than SSD with maildir.

I hope that this offers some clarity. Let us know if you have any other questions!
 

maquinadigital

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Aug 10, 2006
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Hello,

performance wise I also think it's better. My concern is the mdbox rotation when a message gets deleted. The 10MB file (10MB being an example) gets re-written even on a 2KB message delete. Not use if that will impact SSD durability.
thanks for your feedback
 

HostNoc

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Feb 20, 2020
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Hi
With maildir it could just delete the individual email file(s) but with mdbox you've got -many- messages saved in a single file.
The following settings in WHM >> Mailserver Configuration are relevant to the automatic deletion of emails in the Trash folders when using the mdbox format:

Auto Expunge Trash
Trash Expire Time
 

maquinadigital

Well-Known Member
Aug 10, 2006
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Hi
With maildir it could just delete the individual email file(s) but with mdbox you've got -many- messages saved in a single file.
The following settings in WHM >> Mailserver Configuration are relevant to the automatic deletion of emails in the Trash folders when using the mdbox format:

Auto Expunge Trash
Trash Expire Time
And that is my concern. When rotating, if a 1MB message inside a 10MB MDBOX file was deleted, a new 9MB file is written, thus, "consuming" the expected TBW of the SSD drive.
 

cPJustinD

Administrator
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Jan 12, 2021
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Hello again. I can certainly understand the need to reduce the writes to disk; however, I did check with a few colleagues on this, and they agree that mdbox would still be a better choice over maildir.

If you do encounter issues with this conversion, however, please open a support ticket so that we can take a closer look and offer further insight or guidance.

Let us know if you have any other questions!