Time Machine : sda errors

[Nigel Jones]

I have a new 4TB WD 'my passport' drive attached to my RT-AC3200 via USB3.
I enabled Time Machine, and started a mac backup running.
All looks fine, but I happened to look at the router log and see frequency
Jan 28 21:06:38 kernel: end_request: I/O error, dev sda, sector 97241056
or similar
firmware is 3.0.0.4.382_50010

dmesg shows:
end_request: I/O error, dev sda, sector 99265440

end_request: I/O error, dev sda, sector 99265440

sd 0:0:0:0: [sda] Result: hostbyte=DID_OK driverbyte=DRIVER_SENSE

sd 0:0:0:0: [sda] Sense Key : Illegal Request [current]

sd 0:0:0:0: [sda] Add. Sense: Invalid command operation code

sd 0:0:0:0: [sda] CDB: Write same(16): 93 08 00 00 00 00 05 eb 61 a0 00 00 01 80 00 00

end_request: I/O error, dev sda, sector 99312032

end_request: I/O error, dev sda, sector 99312032

sd 0:0:0:0: [sda] Result: hostbyte=DID_OK driverbyte=DRIVER_SENSE

sd 0:0:0:0: [sda] Sense Key : Illegal Request [current]

sd 0:0:0:0: [sda] Add. Sense: Invalid command operation code

sd 0:0:0:0: [sda] CDB: Write same(16): 93 08 00 00 00 00 05 eb e4 a0 00 00 01 80 00 00

end_request: I/O error, dev sda, sector 99345568

end_request: I/O error, dev sda, sector 99345568

sd 0:0:0:0: [sda] Result: hostbyte=DID_OK driverbyte=DRIVER_SENSE

sd 0:0:0:0: [sda] Sense Key : Illegal Request [current]

sd 0:0:0:0: [sda] Add. Sense: Invalid command operation code

sd 0:0:0:0: [sda] CDB: Write same(16): 93 08 00 00 00 00 05 ec 46 20 00 00 01 00 00 00

end_request: I/O error, dev sda, sector 99370528

end_request: I/O error, dev sda, sector 99370528

 

[ColinTaylor]

I understand what the error says, but not the implication (I'm not an Apple person).

The router is sending a "Write same(16)" command to the storage device. The storage device is responding with "I don't support that".

Perhaps when the command fails the router falls back to a traditional sequential write operation. Who knows?

More information on write same is here.

Verify your data is safe by saving and restoring some large files, particularly those that contain large sequences of bytes that are all the same.

Something to do with sparse files perhaps?

 

[bbunge]

Format the drive with EXT3 or 4 or use a Mac format.

Sent from my P01M using Tapatalk

 

[Nigel Jones]

Thanks for the replies. I found a similar thread on the asus forums
From what I can see so far it looks somewhat cosmetic, or even a kernel bug, but it's intriguing to know if anyone else sees this with other drives, or perhaps it's Western Digital specific (in which case I may return the drive and change to seagate etc)

The point about formatting is an interesting one too. The drive is mostly going to be left connected to the asus (and if I get too many issues there would probably go to the raspberry pi next) rather than direct connect to mac, or windows. So rather than NTFS, ext4 could be an option. Being more native perhaps it is a better choice, though I'm not sure it would change this issue (but who knows, if as is mentioned it might relate to ntfs sparse files for example)

 

[bbunge]

Stick with the WD drive. Seagate has a much higher failure rate. I have run EXT3 USB2 drives in two Asus routers with good success. Granted, they were 1 TB drives. Asus does have a limit on the size of USB drive which may be 4 TB for your router. It is more related to router memory. Your router should allow you to format the drive to HFS which may be best for your Mac backup. I have used my drive to run time machine from my iMac but decided to go to a USB drive attached to the iMac.
You might also try your drive in the USB2 port.

Sent from my P01M using Tapatalk

 

[sfx2000]

If the drive is still from the factory with it's partition map - repartion the drive, and then format - EXT3 works well with AsusWRT, however, if using the drive on devices other than Linux, then consider NTFS.

4TB is close to the upper limits - this is mostly due to memory considerations, and TimeMachine can be extremely IO intensive when it starts to "trim" the sparse bundle over time...

Best options for TimeMachine using the drive local on the Mac, second would be OSX server (which is cheap these days), and there's always TimeCapsule - the 4th Gen (802.11n) are fairly cheap second hand on eBay/Craigslist and they work great - turn off the WiFi on them (or use them as an N900 class AP).