Those are cabling errors.
The fact that you 'see' this in the SMART output is normal; post the SMART output here to get relevant replies. The raw value is the place to look at. If it is above 0, then you had cable errors in the past.
It does not mean you still have cabling errors, though. Only if the value keeps increasing, this will be the case. So keep an eye on the raw value and make a copy of your SMART output periodically.
CRC error is showing interference somewhere, could be cable, power supply, nearby florescent lights, static electricity....
is it a major issue?
Take a look at this. What is the source of the problem?
How are all the numbers the exact same for each category?
https://www.dropbox.com/s/unvp9vmdknl88sl/SMART errors on USB drive.png?dl=0
BTW Sorry not trying to hijack your thread.
now it is but in the past it weasnt
CRC counter never goes back down, only increments up AFAIK. Most likely you have to update your program's drive database. Gotta be a software error. Or its the OS or BIOS doing power saving stuff to the USB link. Either way the drive looks perfectly fine.
Well, depends on the case, but if you see 'current pending sectors', 'realocation events', 'offline uncorrectable' rise from 0 then expect instability. Overall, if you repair the connection and perform a full drive scan and then shutdown the computer then it should clear the 'media related' errors back to 0, because it'll have an opportunity (during the full scan) for a 'second look' and if the sector is good and the error was interface related.
In your case I would say it could be either. Start by getting something like HDD guardian - it sits in your tray and monitors changes in SMART params. Set it to report UDMA CRC and you're set.
Remove excess /unneeded USB devices to free power in the hub for the time being.
If that doesn't help, change the USB cable.
patrickdk, i think that is not really correct.
In my experience:
ECC corrected means ECC error correction was necessary to read the sector properly (i.e. without bits being flipped/corrupted). Not all reads require ECC, but many reads do since harddrives with high data density have long passed the point of being able to do their job without ECC. ECC is mandatory today. Unlike DRAM memory for example which can do without and ECC is just a plus to increase reliability to levels enterprise users feel comfortable with.
Current Pending Sector are sectors where after applying ECC the data is still no good. If there was more ECC correcting bits available, the data might be reconstructed properly, but with the ECC ability available, it is not enough and the entire sector is rejected. The ATA standard prohibits the drive from returning data to the host which is known to be corrupt. So the drive will return an I/O error instead after it gives up sector recovery. But it will not forfeit the ability to recover the data - meaning it will not do anything like overwrite or replace that sector - unless either 1) the data is successfully read (rare) or 2) the data is overwritten by the host. Upon 2) the disk will try to read the sector again. If it reads back normal, the sector stays in use and is NOT swapped with a reserve sector (sector reallocation). Only if after overwriting the sector still cannot be read, it counts as physically damaged and will be replaced by the drive - i.e. swapped for a reserve sector.
In the case that the sector is reallocated, the Reallocated Sector Count is increased. But in about 90% of bad sectors today, they are only unreadable due to limited ECC available - known as uBER bad sectors. This is specified by the drive as uncorrectable Bit-Error Rate (uBER) and most consumer drives get 10^-14 which means up to 1 bad sector per day at 100% duty cycle, or once per 4-6 months with light consumer usage. This concerns healthy sectors - not sectors with physical damage. The drive is basically designed to cause unreadable sectors. Enterprise drives get up to 10^-16 uBER specification, meaning this problem is up to 100 times less, causing a factor 100 less bad sectors. Again, this concerns bad sectors that are NOT physically damaged. And uBER can fluctuate wildly with specific drives - it is only roughly valid for very large groups of disks.
Offline Uncorrectable is the same as Current Pending Sector but is not updated immediately (online) but instead of updated only periodically (offline). This can reveal evidence where upon overwriting unreadable sectors all evidence ine SMART had disappeared. The Current Pending Sector is reset back to 0, but when no sectors are swapped for reserve sectors, Reallocated Sector Count also stays at 0. Only the Offline Uncorrectable can betray that there were actually bad sectors in the recent past. I personally think SMART should be extended with a counter that never is reset, but counts the total number of unreadable sectors, much like UDMA CRC Error Count works for cabling errors. The raw value for this attributed is never reset either, but just stays at its value if no further cabling errors occur.
Well i have 32GiB RAM at three of my NAS systems which use ZFS. This means memory bitflips will be detected in the form of disk corruption. Not one checksum error has arisen in the many years of service (4-5 years i think). So ECC for RAM is nice but in many circumstances you can do without.
If you say more than one bitflip per day i really would like to see a source on that. Because if that is true, then virtually all systems would become unusable/unstable and ZFS would generate tons of checksum errors 'daily' which is simply not true. I do know RAM bitflips are dependent on the duty cycle though. Many consumer-grade systems have very low duty cycle (1-2%) while heavily used servers can push beyond 50%.
ok nm i see what is being talked about now...sorry i got lost on who was referring to wahtI failed to see what I said was wrong.
ECC error, it read the disk fine, with small amount of corruption.
If the read was worse, could be alignment issue or worse, the disk was not read fine, it is having major issues.
This description is pretty much accurate, but concerns Current Pending Sector instead. Also, it will apply to the first unsuccessful read attempt - often having triggered recovery. But the recovery can be interrupted by a RESET command.offline uncorrectable, is a sector it has had to retry reading many many times, and is too damaged for ECC to fix it.
This appears to suggest that all 'Current Pending Sectors' are physically damaged and will be swapped for a reserve sector when overwritten. This, however, is not true. In fact, about 90% of pending sectors are without physical damage and will NOT be swapped for a reserve sector when overwritten. It will simply keep being used, because the sector itself is not damaged or anything. It just had bit errors that exceeded the ECC correcting capability. And upon overwriting/refreshing the sector, it will read back normal without exceeding the ECC capability.current pending sectors, is an offline uncorrectable that has been marked as damaged beyond repair and recovery attempts, and is waiting for a write for it to be reallocated.
Current pending sectors, WILL get reallocated when written to.
However some drives will not immediately remap such sectors when written; instead the drive will first attempt to write to the problem sector and if the write operation is successful then the sector will be marked good (in this case, the "Reallocation Event Count" (0xC4) will not be increased).
They generally are true for all recent consumer-grade drives by a simple function of mathematics. Consumer-grade drives get specified uBER 10^-14. For lower capacities and duty cycles, this results in very few bad secors due to insufficient ECC correcting capability, but with todays drives with very high data density and high throughput, the same 10^-14 specification results in up to one bad sector per day (100% duty cycle), on average, when testing many samples over a long period of time. These bad sectors are not due to physical damage, but simply because of insufficient ECC correcting capability.Little of that is necessarily true. It may be true for some drives from some manufacturers, but it is not true for all drives from all manufacturers. Statements like "90% of pending sectors are without physical damage" are not useful, since if they are correct at all, they are only correct for certain drives from certain manufacturers under certain conditions.
Possibly, but i have not had one confirmed case where this was the case. Current Pending Sector, Reallocated Sector Count and UDMA CRC Error Count all seem to behave equal on all drives i ever saw the SMART output for, in all my years of experience.One of the problems with SMART attributes is that they are not well-defined, and can vary a lot between manufacturers. When you get into the sorts of specifics that you are mentioning, you are going to be incorrect for some -- and probably many -- drives.
What i understand of 198 (Offline Uncorrectable) is that it is the same as Current Pending Sectors - which often get detected by host reads, not by SMART tests - but that this SMART attribute gets collected/updated offline, and not online like Current Pending Sector (197).Note that attribute 198 is not necessarily ONLY uncorrectable sectors detected during off-line SMART testing. Some manufacturers include in attribute 198 uncorrectable sectors detected during off-line SMART testing, during SMART self-test, or during drive operation, or some combination.
Are you sure this is correct? Because in my experience there is no difference in how drives handle Current Pending Sector.Attribute 197 also can vary between drives. More specifically, the way the count gets decremented varies. The way the count increments is fairly consistent among drives (it gets incremented when there is an uncorrectable read error, UNC). As for decrementing it, that can happen if the drive tries to read a previously UNC and successfully reads it -- in that case the drive will usually reallocate the sector and write the newly read value to the remapped sector. However, some drives may try to rewrite the same sector that was previously UNC. Another way it can be decremented is if there is a write request to the sector, then the drive will possibly reallocate the sector. But it may also try to write the previously UNC sector, and if the write succeeds, then it will not reallocate the sector but just use the old sector and decrement the pending count.
There is, they are included in the SMART 'flags' which indicate what those attributes do.And there is no such distinction as "offline" and "online" SMART attributes
SMART Attributes Data Structure revision number: 10 Vendor Specific SMART Attributes with Thresholds: ID# ATTRIBUTE_NAME FLAGS VALUE WORST THRESH FAIL RAW_VALUE 197 Current_Pending_Sector -O--C- 100 100 000 - 0 198 Offline_Uncorrectable ----C- 100 100 000 - 0 ||||||_ K auto-keep |||||__ C event count ||||___ R error rate |||____ S speed/performance ||_____ O updated online |______ P prefailure warning
The O flag here describes the attributes as being updated on-the-fly or Online, while without O flag it would be offline like Offline Uncorrectable in the example above (Toshiba drive).