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0 pointskstrauser1y ago0 comments

You absolutely, positively, 100% need it on anything that carries data you care about. I personally consider it a hard requirement for a NAS. I don't want to lose data just because a cosmic ray flipped a bit somewhere.

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Dylan168071y ago

There's a lot of places the file can get corrupted on its way to your drive. The memory of the NAS itself is only one of those. If you want any certainty you need to verify it after writing, so ECC RAM is not enough. And once you do set up that verification, you don't need the ECC RAM anymore.

ClumsyPilot1y ago

I am not sure this is correct - there could be an error not only in the data, but also in instructions - but flip could cause data to be written to an incorrect location of the hard disk.

Dylan168071y ago

Possible, but I bet the risk of writing/losing the wrong sector based on that kind of RAM bit flip is a lot less than the other sources of writing/losing the wrong sector.

rullopat1y ago

Can you tell us HOW to setup a NAS so that it doesn't need ECC RAM?

Dylan168071y ago

That differs based on the program you're using to put files onto the NAS.

But I'll note the even with ECC you need to double check things in case there was corruption on the drive wires or in many other places. With the right filesystem you can find some of those locally during a scrub, but double checking end-to-end isn't much harder.

PhilipRoman1y ago

Storing error correcting codes/checksums/signatures and sending them along the data seems like a more cost effective solution. Without those you need to ensure that every single link in the chain supports ECC (and all the hardware works perfectly)

ECC may still be needed for the actual processing, but I don't see a point on having it on a NAS (especially considering you need to send the data over a network to read or write it)

kevinkeller1y ago

> I don't want to lose data just because a cosmic ray flipped a bit somewhere.

If you have disks set up in RAID 1 or RAID 6, would you still lose data though?

extesy1y ago

Absolutely. Imagine you are saving a text file to NAS with a super-secret password to your Bitcoin wallet, for example "password". While it was in memory before it reached disk, one bit was flipped and the file contents became "pastword" which OS happily saved on your RAID. And now you've lost your Bitcoins forever.

benlivengood1y ago

In raid1 all you need is a bit flip in RAM between writing to disks to cause a permanent error (one disk gets the flipped bit, the other does not).

Raid6 will repair single bit errors, assuming a bit wasn't flipped before/during the erasure code calculation when writing the data.

ttyprintk1y ago

Consider all the RAM along a network transmission. Maybe you’re using authenticated encryption, maybe your transfer has an internal or out of band checksum. Maybe not.

j / k navigate · click thread line to collapse

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Dylan168071y ago

ClumsyPilot1y ago

I am not sure this is correct - there could be an error not only in the data, but also in instructions - but flip could cause data to be written to an incorrect location of the hard disk.

Dylan168071y ago

Possible, but I bet the risk of writing/losing the wrong sector based on that kind of RAM bit flip is a lot less than the other sources of writing/losing the wrong sector.

rullopat1y ago

Can you tell us HOW to setup a NAS so that it doesn't need ECC RAM?

Dylan168071y ago

That differs based on the program you're using to put files onto the NAS.

PhilipRoman1y ago

ECC may still be needed for the actual processing, but I don't see a point on having it on a NAS (especially considering you need to send the data over a network to read or write it)

kevinkeller1y ago

> I don't want to lose data just because a cosmic ray flipped a bit somewhere.

If you have disks set up in RAID 1 or RAID 6, would you still lose data though?

extesy1y ago

benlivengood1y ago

In raid1 all you need is a bit flip in RAM between writing to disks to cause a permanent error (one disk gets the flipped bit, the other does not).

Raid6 will repair single bit errors, assuming a bit wasn't flipped before/during the erasure code calculation when writing the data.

ttyprintk1y ago

Consider all the RAM along a network transmission. Maybe you’re using authenticated encryption, maybe your transfer has an internal or out of band checksum. Maybe not.

j / k navigate · click thread line to collapse