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  1. #61
    Senior Member chill's Avatar
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    Brilliant - thanks Greg, just was I was looking for. Right now I'm half way through re-syncing my backup copy from my main copy, having reformatted the backup disk as ext4. Once that completes and I'm happy that it's a complete and correct backup, I plan to reformat my main disk as ext4 as well and re-sync that from the backup (I do also have another backup in case of blunders!). Hopefully this will be an end to the timezone ambiguity.

    Regarding the ext4 format, my main disk is an SSD, and I've read that it could be useful to turn off journaling to save wear on the memory. But given that the majority of the content on this disk is static (content only changes when I buy a new CD), is journaling going to be an issue? Are there still a lot of journaling disk writes when the content is only being read, not written? My backup disk (a conventional hard disk disk) seems to mount with -noatime by default, so I don't believe there should be any disk writes most of the time, but I don't know what extra is written by a journaling system.

  2. #62
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    Quote Originally Posted by chill View Post
    Maybe I should just use a disk format more suited to Linux. I started out with the intention of being as compatible as possible across different operating systems, but I'm not sure that's really necessary - I'll always have something that can read a Linux disk.
    "Compatible" is why I'm using FAT for my library. I do periodically mount it directly under macOS.

    I've never looked at exFAT. Google tells me that it does support recording the timezone offset together with "DOS time", and the 10ms granularity noted above. Not clear if all OS implementations support the timezone feature, though.

  3. #63
    Senior Member chill's Avatar
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    Thankyou. Compatibility used to be a major concern for me, when I had a Windows desktop at home, a Macbook for work and a Mac Mini running LMS. And Linux just scared me! The Windows desktop was retired years ago, that original Macbook now dual boots into MacOS and Ubuntu, and thanks to the ease of using pCP I've also retired the Mac Mini. I've never looked back. I'm starting to find my feet with Linux, and the thought of having 'Linux-only' drives no longer scares me.

    So now I have my master library on an ext4 SSD (with journaling switched off), my backup library on a separate ext4 hard disk, and my compressed mirror in a separate folder on that disk. That compressed mirror folder will act as the source for making a flash copy for mobile use, and I'm currently rsyncing it to a third partition on the mobile RPi's SD card, also formatted as ext4 without journaling. With a bit of luck, 'timezone hell' is now a thing of the past (no doubt to be replaced by 'permissions' hell).

    As an aside, given that my overnight cron job updates the backup copy from the master copy, and the compressed mirror from the backup copy, I should probably also keep an occasional off-site archive of the master copy, since any file errors/loss in the master copy will quickly propagate to the other copies.

  4. #64
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    Quote Originally Posted by chill View Post
    Regarding the ext4 format, my main disk is an SSD, and I've read that it could be useful to turn off journaling to save wear on the memory. But given that the majority of the content on this disk is static (content only changes when I buy a new CD), is journaling going to be an issue?
    I'd strongly advise against disabling the journal - the miniscule reduction of write accesses isn't worth the increased risk of data loss / corruption.
    Even older SSD models can write huge amounts of data before getting flaky (see here and here for some tests). Newer ones are usually even better.

    Are there still a lot of journaling disk writes when the content is only being read, not written? My backup disk (a conventional hard disk disk) seems to mount with -noatime by default, so I don't believe there should be any disk writes most of the time, but I don't know what extra is written by a journaling system.
    Nothing extra is written by a journaling system - the journal is only updated on writes, not reads.
    I'd suggest these mount options for ext4 on a SSD:
    Code:
    noatime,lazytime,discard
    to minimize writes / improve performance

  5. #65
    Senior Member chill's Avatar
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    Thanks Roland - Am I right that files that are only being read won't have any risk of being lost or corrupted anyway (at least, not in a way that a journal can help with)? So journaling will only guard against loss when files are being written, and for a disk with almost static content this is a very small risk?

    But your point about journaling adding only a small amount of writes is well taken, so I'll see if I can turn it back on.

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