5 ms·

Synology became so bad, they measure disk space in percent, and thresholds cannot be configured to lower than 5%. This may have been okay when volume sizes were

Synology became so bad, they measure disk space in percent, and thresholds cannot be configured to lower than 5%. This may have been okay when volume sizes were in gigabytes, but now with multi-TB drives, 5% is a lot of space. The result of that is NAS in permanent alarm state because less than 5% space is free. And this makes it less likely for the user to notice when an actual alarm happens because they are desensitised to warnings. I submitted this to them at least four times, and they reply that this is fine, it’s already decided to be like that, so we will not change it. Another stupid thing is that notifications about low disk space are sent to you via email and push until it’s about 30 GB free. Then free space goes below 30 GB and reaches zero, yet notifications are not sent anymore. My multiple reports about this issue always responded along the lines of “it’s already done like that, so we will not change it”. Most modern, especially software companies, choose not to fix relatively small but critical problems, yet they actively employ sometimes hundreds of customer support yes-people whose job seems to be defusing customer complaints. Nothing is ever fixed anymore.

pixelesque 1y ago
Not defending them in any way, but I know with my Infrant (then Netgear unfortunately, who last year killed the products) ReadyNASs which also used mdadm to configure BTRFS with RAID5 in a similar way to Synology and QNAP, the recommendation was that you don't want your BTRFS filesystem to run low on space, because then it runs out of metadata space, and if it does that it becomes read-only, and can become unstable. Basically, the recommendation was to always have 5% free space, so this isn't just Synology saying this.
- pixelesque 1y ago
  Actually, reading the BTRFS docs, they recommend keeping 5-10% free space: https://archive.kernel.org/oldwiki/btrfs.wiki.kernel.org/index.php/SysadminGuide.html#Balancing https://archive.kernel.org/oldwiki/btrfs.wiki.kernel.org/ind...
  - MrDrMcCoy 1y ago
    Yup. After having dealt with that, I err on the side of caution and don't even let it merge small files into inodes for space savings. I still love btrfs for the CoW, snapshots, and compression, but you really gotta give that metadata a wide berth.
- magicalhippo 1y ago
  ZFS has a similar limitation. It tries to mitigate this by reserving some space for metadata, to be used in emergencies, but apparently it's possible to exhaust it and get your filesystem into a read-only state. There was some talk about increasing the reservations to prevent this but can't recall if changes were made.
- izacus 1y ago
  The recommendation of 5% free space comes from arrays in sizes of 100s of GB, not tens of TB. This is the same kind of issue that Linux root filesystems had - a % based limitation made sense when disks were small, but now they don't make a lot of sense anymore when they restrict usage of hundreds of GB (which are not actually needed by the filesystem to operate).
kbolino 1y ago
I think preventing alarm fatigue is a very good reason to fix issues. But 5% free is very low. You may want to use every single byte you feel you paid for, but allocation algorithms really break down when free space gets so low. Remember that there's not just a solid chunk of that 5% sitting around at the end of the space. That's added up over all the holes across the volume. At 20-25% free, you should already be looking at whether to get more disks and/or deciding what stuff you don't actually need to store on this volume. So a hard alarm at 5% is not unreasonable, though there should also be a way to set a soft alarm before then.
- sitkack 1y ago
  [flagged]
- kimixa 1y ago
  Also Synology use btrfs, a copy-on-write filesystem - that means there are operations that you might not expect that require allocation of new blocks - like any write, even if overwriting an existing file's data. And "unexpected" failure paths like that are often poorly tested in apps.
- leptons 1y ago
  No matter how many TB of online HD storage I have, hard disks are just a temporary buffer for my tape drives.
  - worthless-trash 1y ago
    This is an area that i'm quickly growing into, what are you curently using and what should I stay away from ?
    - leptons 1y ago
      I got a used internal LTO5 tape drive on eBay for about $150, and then an HBA card to connect it to for about $25 or $30. I bought some LTO5 tapes, and typically I pay about $3.50/TB on eBay for new/used tapes. Many sellers charge far more for tapes, but occasionally I find a good deal. Most tapes are not used very much and have lots of life left in them (they have a chip inside the tape that tracks usage). Then I scored another 3 used LTO5 tape drives on eBay for about $100, they all worked. I mainly use 1 tape drive. I have it running on an Intel i5 system with an 8-drive RAID10 array (cheap used drives, with a $50 9260-8i hardware RAID card), which acts as my "offsite" backup out in my detached garage - it's off most of the time (cold storage?) unless I'm running a backup. I can loose up to 2 drives without losing any data, and it's been running really well for years. I have 3 of these RAID setups in 3 different systems, they work great with the cheapest used drives from Amazon. I'm not looking for high performance, I just need redundancy. I've had to replace maybe 3 drives across all 3 systems due to failure over the last 7 years. On Windows the tape drive with LTFS was not working well, I think due to Windows Defender trying to test the files as it was writing them, causing a lot of "shoeshining" of the tape, but I think Windows Defender can be disabled. But I bought tape backup software from https://www.iperiusbackup.com https://www.iperiusbackup.com - it just works and makes backups simple to set up and run. I always verify the backup. If something is really important I'll back up to at least 2 tapes. Some really important stuff I will generate parity files (win WinPar) and put those on tape too. Non-encrypted the drive runs at the full 140MB/s, but with encryption it runs at about 60MB/s, because I guess the tape drive is doing the encryption. I love it, it has changed my data-hoarding life. At $3.50/TB and 140MB/s and 1.5TB per tape, it can't be beat by DVD-R or hard drives for backup. Used LTO5 is really in a sweet spot right now on eBay, but LTO6 is looking good too recently (2.5TB/tape). LTO6 drives can read LTO5 tapes, so there's a pretty easy upgrade path. I also love that there is a physical write-protect switch on the tapes, which hard drives don't have. If you plug in a hard drive to an infected system, that hard drive could easily be compromised if you don't know your system is infected.

pixelesque 1y ago

Not defending them in any way, but I know with my Infrant (then Netgear unfortunately, who last year killed the products) ReadyNASs which also used mdadm to configure BTRFS with RAID5 in a similar way to Synology and QNAP, the recommendation was that you don't want your BTRFS filesystem to run low on space, because then it runs out of metadata space, and if it does that it becomes read-only, and can become unstable. Basically, the recommendation was to always have 5% free space, so this isn't just Synology saying this.

pixelesque 1y ago
Actually, reading the BTRFS docs, they recommend keeping 5-10% free space: https://archive.kernel.org/oldwiki/btrfs.wiki.kernel.org/index.php/SysadminGuide.html#Balancing https://archive.kernel.org/oldwiki/btrfs.wiki.kernel.org/ind...
- MrDrMcCoy 1y ago
  Yup. After having dealt with that, I err on the side of caution and don't even let it merge small files into inodes for space savings. I still love btrfs for the CoW, snapshots, and compression, but you really gotta give that metadata a wide berth.
magicalhippo 1y ago
ZFS has a similar limitation. It tries to mitigate this by reserving some space for metadata, to be used in emergencies, but apparently it's possible to exhaust it and get your filesystem into a read-only state. There was some talk about increasing the reservations to prevent this but can't recall if changes were made.
izacus 1y ago
The recommendation of 5% free space comes from arrays in sizes of 100s of GB, not tens of TB. This is the same kind of issue that Linux root filesystems had - a % based limitation made sense when disks were small, but now they don't make a lot of sense anymore when they restrict usage of hundreds of GB (which are not actually needed by the filesystem to operate).

kbolino 1y ago

I think preventing alarm fatigue is a very good reason to fix issues. But 5% free is very low. You may want to use every single byte you feel you paid for, but allocation algorithms really break down when free space gets so low. Remember that there's not just a solid chunk of that 5% sitting around at the end of the space. That's added up over all the holes across the volume. At 20-25% free, you should already be looking at whether to get more disks and/or deciding what stuff you don't actually need to store on this volume. So a hard alarm at 5% is not unreasonable, though there should also be a way to set a soft alarm before then.

sitkack 1y ago
[flagged]
kimixa 1y ago
Also Synology use btrfs, a copy-on-write filesystem - that means there are operations that you might not expect that require allocation of new blocks - like any write, even if overwriting an existing file's data. And "unexpected" failure paths like that are often poorly tested in apps.
leptons 1y ago
No matter how many TB of online HD storage I have, hard disks are just a temporary buffer for my tape drives.
- worthless-trash 1y ago
  This is an area that i'm quickly growing into, what are you curently using and what should I stay away from ?
  - leptons 1y ago
    I got a used internal LTO5 tape drive on eBay for about $150, and then an HBA card to connect it to for about $25 or $30. I bought some LTO5 tapes, and typically I pay about $3.50/TB on eBay for new/used tapes. Many sellers charge far more for tapes, but occasionally I find a good deal. Most tapes are not used very much and have lots of life left in them (they have a chip inside the tape that tracks usage). Then I scored another 3 used LTO5 tape drives on eBay for about $100, they all worked. I mainly use 1 tape drive. I have it running on an Intel i5 system with an 8-drive RAID10 array (cheap used drives, with a $50 9260-8i hardware RAID card), which acts as my "offsite" backup out in my detached garage - it's off most of the time (cold storage?) unless I'm running a backup. I can loose up to 2 drives without losing any data, and it's been running really well for years. I have 3 of these RAID setups in 3 different systems, they work great with the cheapest used drives from Amazon. I'm not looking for high performance, I just need redundancy. I've had to replace maybe 3 drives across all 3 systems due to failure over the last 7 years. On Windows the tape drive with LTFS was not working well, I think due to Windows Defender trying to test the files as it was writing them, causing a lot of "shoeshining" of the tape, but I think Windows Defender can be disabled. But I bought tape backup software from https://www.iperiusbackup.com https://www.iperiusbackup.com - it just works and makes backups simple to set up and run. I always verify the backup. If something is really important I'll back up to at least 2 tapes. Some really important stuff I will generate parity files (win WinPar) and put those on tape too. Non-encrypted the drive runs at the full 140MB/s, but with encryption it runs at about 60MB/s, because I guess the tape drive is doing the encryption. I love it, it has changed my data-hoarding life. At $3.50/TB and 140MB/s and 1.5TB per tape, it can't be beat by DVD-R or hard drives for backup. Used LTO5 is really in a sweet spot right now on eBay, but LTO6 is looking good too recently (2.5TB/tape). LTO6 drives can read LTO5 tapes, so there's a pretty easy upgrade path. I also love that there is a physical write-protect switch on the tapes, which hard drives don't have. If you plug in a hard drive to an infected system, that hard drive could easily be compromised if you don't know your system is infected.