1 TB portable HD doesn't stop reading an writing if formatted with ext4
 

Has this ever happened to you?

I've bought a 1 TB portable HD which I pretend to use for backups.

I've partitioned it GPT, and I wanted to format a big partition (about 900 GB) with ext4, but when I mount it, the led which indicates that the drive is working doesn't stop; it keeps blinking all the time.

This doesn't happen if I format the same partition with ext2 or ext3. I'd like to preserve this HD in good working condition as much as possible. I'm afraid this constant reading-writing behavior could damage it.

What is happening?. Could I tune the ext4 filesystem in any way to prevent this?. Or Should I better format the HD with ext2 or ext3?.

Thanks in advance for any help.

I also have a 1 TB portable HD which I have formated into 4 250 GB partitions. It is a Iomega Prestige Desktop Hard Drive model 34919. I use this drive for backups and it is disconnected and turned off most of the time. When I leave the hard drive turned on and plugged in but unmounted the read/write light sometimes blinks continuously. I don't know why it blinks and I have used this drive for over a year with no problems. Whenever it starts blinking I unplug it and turn it off.

I bought this drive on Amazon and read the reviews before I bought it. One of the reviewers described this type of behavior on his external hard drive but he could find no problems created by the drive's occasional self generated activity.

"I'm afraid this constant reading-writing behavior could damage it."

I agree. That's why I always turn it off when not in use. Have you had any problems with the drive other than being perplexed by its behavior?

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Steve Stites

No, no more problems, but I have not used it seriously, still. I've just partitioned, made the filesystem and mounted it (to discover the led blinking continuously).

If I'm going to use it for backups, I'd like to be sure that it will work right, for as long as possible. My plan was to rsync my /home every 20 minutes, via a shell script in crontab. Then this drive would only have to work a little, every 20 minutes.

If we both have this problem with ext4, ...could it be a bug?. I wonder if the developers are aware of this.

If no one can suggest some tuning options to make the filesystem work... properly (?), I think I'll just use ext2 or ext3. Maybe I can sacrifice performance for durability, in this case.

"If we both have this problem with ext4, ...could it be a bug?. I wonder if the developers are aware of this."

I can get the problem by powering up the drive and never connecting it to my USB port. The problem on my drive is intermittent. Intermittents are characteristic of hardware rather than software. So I think it is probably a hardware problem. I only run the drive about 10 minutes a day so turning it off the rest of the time works. Sometimes I forget to power it off after doing a backup and sometime during the next hour I will notice the read-write light flickering. I sometimes notice the flickering when I power the drive up and don't get around to doing the backup for a while.

I never thought to try ext2 and ext3. The way that ext4 handles dirty cache buffers is different than the way ext3 handles them so conceivable there could be a problem in ext4 writes that does not exist in ext3. Before you reach that conclusion you should run ext3 for a lengthy period and see if a hardware intermittent shows up.

Another test would be to format the partition as ext4 and mount it as ext3. ext4 has enough backward compatibility that you can run ext4 as ext3 and it just runs slower. See if the problem shows up under these conditions.

The best test is to power up the drive and do not connect it to your computer. Let it run for a while and see if the problem occurs like it does on my drive under this test.

Obviously power off when not in use is not a solution in your case. If you want to fix the problem I suggest you contact the manufacturer first and see what they say. If they say it is software then try the ext4 people.

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Steve Stites

lazy_itable_init
 

Thanks for your answers jailbait, I think I've found it:

By default, an ext4 filesystem is created with the lazy_itable_init option enabled (more info in the man page). What does this mean?.

The inode table is not initialized when the filesystem is created (which speeds up filesystem creation), but the kernel will have to initialize the filesystem in the background when it will be first mounted.

I guess that while the bigger the filesystem, this reading-writing behavior will last for longer, and if it is in a backup USB drive like mine, it will be more noticeable than my system's HD current read-write operations.

As a reference, in a 855 GiB ext4 filesystem it stopped in less than 2 hours.

I still wonder what happens if you umount the filesystem before it ends up initializing the inode table for the first time.

I hope I've been helpful to any readers, if so, add to my reputation :D

I'll mark this thread as solved as soon as I find a way to edit the tittle, I promise.