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Massimo B.
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 Posted: Sun Mar 31, 2024 5:22 pm Post subject: Discard over USB |
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Hello,
this is the discussion thread about https://wiki.gentoo.org/wiki/Discard_over_USB ...
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Massimo B.
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Joined: 09 Feb 2005
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Location: PB, Germany
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| Posted: Sun Mar 31, 2024 5:54 pm Post subject: |
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From this wiki I learned, that trim via USB bridges is not trivial.
I'm using btrfs on LUKS on all my devices that are HDDs, SATA SSDs and NVMe SSDs.
I came to investigate trim and discard further as sometimes by BTRFS is blocking all IO right after booting:
https://lore.kernel.org/linux-btrfs/238dc2b36f27838baf02425b364705c58fcc5de5.camel@gmx.net
The mount option discard maybe envolved in this issue so I disabled that on all devices...
What happens if an USB bridge does not support trim? Someday the SSD can't write anymore without moving to another controler to get the trim done?
I have a Ugreen SSD M.2 NVMe enclosure with USB 3.1 Gen2. Following the Wiki it first looks like supporting trim but then it fails:
| Code: | # lsusb.py |grep Ugreen
4-6 0bda:9210 00 1IF [USB 3.20, 5000 Mbps, 896mA] (Ugreen Ugreen Storage Device 0129380014F4)
# lsusb |grep 9210
Bus 004 Device 004: ID 0bda:9210 Realtek Semiconductor Corp. RTL9210 M.2 NVME Adapter
# eix -Ic usbutils
[I] sys-apps/usbutils (017@19.01.2024): USB enumeration utilities |
| Code: | # find /sys/ -name provisioning_mode -exec grep -H . {} + | sort
/sys/devices/pci0000:00/0000:00:14.0/usb2/2-14/2-14:1.0/host6/target6:0:0/6:0:0:0/scsi_disk/6:0:0:0/provisioning_mode:full
/sys/devices/pci0000:00/0000:00:14.0/usb2/2-14/2-14:1.0/host6/target6:0:0/6:0:0:1/scsi_disk/6:0:0:1/provisioning_mode:full
/sys/devices/pci0000:00/0000:00:14.0/usb2/2-14/2-14:1.0/host6/target6:0:0/6:0:0:2/scsi_disk/6:0:0:2/provisioning_mode:full
/sys/devices/pci0000:00/0000:00:14.0/usb2/2-14/2-14:1.0/host6/target6:0:0/6:0:0:3/scsi_disk/6:0:0:3/provisioning_mode:full
/sys/devices/pci0000:00/0000:00:14.0/usb2/2-14/2-14:1.0/host6/target6:0:0/6:0:0:4/scsi_disk/6:0:0:4/provisioning_mode:full
/sys/devices/pci0000:00/0000:00:14.0/usb2/2-7/2-7:1.0/host7/target7:0:0/7:0:0:0/scsi_disk/7:0:0:0/provisioning_mode:full
/sys/devices/pci0000:00/0000:00:14.0/usb4/4-6/4-6:1.0/host5/target5:0:0/5:0:0:0/scsi_disk/5:0:0:0/provisioning_mode:unmap
/sys/devices/pci0000:00/0000:00:1f.2/ata1/host0/target0:0:0/0:0:0:0/scsi_disk/0:0:0:0/provisioning_mode:writesame_16
/sys/devices/pci0000:00/0000:00:1f.2/ata2/host1/target1:0:0/1:0:0:0/scsi_disk/1:0:0:0/provisioning_mode:full
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I guess this is my device:
| Code: | # find /sys/ -name provisioning_mode -exec grep -H . {} + | sort |grep 4-6
/sys/devices/pci0000:00/0000:00:14.0/usb4/4-6/4-6:1.0/host5/target5:0:0/5:0:0:0/scsi_disk/5:0:0:0/provisioning_mode:unmap |
| Code: | # fdisk -l /dev/sdh
Disk /dev/sdh: 3,64 TiB, 4000787030016 bytes, 7814037168 sectors
Disk model: SN850X 4000GB
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 33553920 bytes
Disklabel type: gpt
Disk identifier: ...
Device Start End Sectors Size Type
/dev/sdh1 2048 73727 71680 35M EFI System
/dev/sdh2 73728 598015 524288 256M Linux filesystem
/dev/sdh3 598016 7814035455 7813437440 3,6T Linux filesystem |
| Code: | # sg_vpd -p bl /dev/sdh
Block limits VPD page (SBC):
Write same non-zero (WSNZ): 0
Maximum compare and write length: 0 blocks [Command not implemented]
Optimal transfer length granularity: 1 blocks
Maximum transfer length: 65535 blocks
Optimal transfer length: 65535 blocks
Maximum prefetch transfer length: 0 blocks [ignored]
Maximum unmap LBA count: 20971520
Maximum unmap block descriptor count: 1
Optimal unmap granularity: 1 blocks
Unmap granularity alignment valid: false
Unmap granularity alignment: 0 [invalid]
Maximum write same length: 0 blocks [not reported]
Maximum atomic transfer length: 0 blocks [not reported]
Atomic alignment: 0 [unaligned atomic writes permitted]
Atomic transfer length granularity: 0 [no granularity requirement
Maximum atomic transfer length with atomic boundary: 0 blocks [not reported]
Maximum atomic boundary size: 0 blocks [can only write atomic 1 block]
# sg_vpd -p bl /dev/sdh |grep "Maximum unmap LBA"
Maximum unmap LBA count: 20971520 |
Up to here, it looks like trim might be supported.
Unmap was already set because I ran the steps already before this post. Anyway, setting again:
| Code: | # echo unmap > /sys/devices/pci0000:00/0000:00:14.0/usb4/4-6/4-6:1.0/host5/target5:0:0/5:0:0:0/scsi_disk/5:0:0:0/provisioning_mode
# echo '20971520*512' | bc
10737418240
# echo $(echo '20971520*512' | bc) > /sys/block/sdh/queue/discard_max_bytes
-bash: echo: write error: Invalid argument
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... and failing here. What can I do? What does this mean?
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NeddySeagoon
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| Posted: Sun Mar 31, 2024 6:13 pm Post subject: |
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Massimo B.
So far so good.
Is using | Code: | | echo 10737418240 > /sys/block/sdh/queue/discard_max_bytes |
any help?
If trim cannot be enabled, the drive will do some clean up, when a write is commanded. It will have to do an erase first.
Trim allows the drive to do the clean up in advance of the write that would force it, thus avoiding the slow erase cycle slowing writes.
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NeddySeagoon
Computer users fall into two groups:-
those that do backups
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Massimo B.
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Joined: 09 Feb 2005
Posts: 1773
Location: PB, Germany
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| Posted: Sun Mar 31, 2024 6:19 pm Post subject: |
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Does that mean, if trim is not supported, that the device is getting slower when getting more bytes written over time, or that every write is just always slower on this USB bridge?
That echo is failing as mentioned above:
| Code: | # echo 10737418240 > /sys/block/sdh/queue/discard_max_bytes
-bash: echo: write error: Invalid argument |
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NeddySeagoon
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| Posted: Sun Mar 31, 2024 6:29 pm Post subject: |
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Massimo B.
What does | Code: | | cat /sys/block/sdh/queue/discard_max_hw_bytes |
tell?
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NeddySeagoon
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Massimo B.
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Joined: 09 Feb 2005
Posts: 1773
Location: PB, Germany
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| Posted: Tue Apr 02, 2024 6:40 am Post subject: |
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| Code: | # echo 10737418240 > /sys/block/sdh/queue/discard_max_bytes
-bash: echo: write error: Invalid argument
# cat /sys/block/sdh/queue/discard_max_bytes
4294966784 |
Does that discard_max_bytes need to know anything about the partitioning and the LUKS device, or does it only see the block device? Why is that set size smaller than expected?
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