On Tue 19 May 2015 10:07:49 AM Thomas Fjellstrom wrote: > On Tue 19 May 2015 10:51:59 AM you wrote: > > On 05/19/2015 10:32 AM, Thomas Fjellstrom wrote: > > > On Tue 19 May 2015 09:23:20 AM Phil Turmel wrote: > > >> Depends. In a properly functioning array that gets scrubbed > > >> occasionally, or sufficiently heavy use to read the entire contents > > >> occasionally, the UREs get rewritten by MD right away. Any UREs then > > >> only show up once. > > > > > > I have made sure that it's doing regular scrubs, and regular SMART > > > scans. > > > This time... > > > > Yes, and this drive was kicked out. Because it wouldn't be listening > > when MD tried to write over the error it found. > [snip] > > > I posted this link earlier, but it is particularly relevant: > > http://marc.info/?l=linux-raid&m=133665797115876&w=2 > > > > >> Interesting. I suspect that if you wipe that disk with noise, read it > > >> all back, and wipe it again, you'll have a handful of relocations. > > > > > > It looks like each one of the blocks in that display is 128KiB. Which i > > > think means those red blocks aren't very far apart. Maybe 80MiB apart? > > > Would it reallocate all of those? That'd be a lot of reallocated > > > sectors. > > > > Drives will only reallocate where a previous read failed (making it > > pending), then write and follow-up verification fails. In general, > > writes are unverified at the time of write (or your write performance > > would be dramatically slower than read). > > Right. I was just thinking about how you mentioned that I'd get a handful of > reallocations based on the latency shown in the image I posted. It's a lot > of sectors that seem to be affected by the latency spikes, so I assumed > (probably wrongly) that many of them may be reallocated afterwards. > > If this drive ends up not reallocating a single sector, or only a few, I may > just keep it around as a hot spare, though i feel that's not the best idea, > if it is degrading, then when it actually goes to use that disk it has a > higher chance of failing. Well here's something: [78447.747221] sd 0:0:15:0: [sdf] FAILED Result: hostbyte=DID_OK driverbyte=DRIVER_SENSE [78447.749092] sd 0:0:15:0: [sdf] Sense Key : Medium Error [current] [78447.751034] sd 0:0:15:0: [sdf] Add. Sense: Unrecovered read error [78447.752925] sd 0:0:15:0: [sdf] CDB: Read(16) 88 00 00 00 00 00 ef 7a 0f b0 00 00 00 08 00 00 [78447.754746] blk_update_request: critical medium error, dev sdf, sector 4017754032 [78447.756700] Buffer I/O error on dev sdf, logical block 502219254, async page read <many many more of the above> 5 Reallocated_Sector_Ct PO--CK 087 087 036 - 17232 187 Reported_Uncorrect -O--CK 001 001 000 - 8236 197 Current_Pending_Sector -O--C- 024 024 000 - 12584 198 Offline_Uncorrectable ----C- 024 024 000 - 12584 Badblocks is showing a bunch of errors now, and the above is what's in dmesg and smartctl. So I guess it was dead after all. > > >> You have it backwards. If you have WD Reds, they are correct out of > > >> the > > >> box. It's when you *don't* have ERC support, or you only have desktop > > >> ERC, that you need to take special action. > > > > > > I was under the impression you still had to enable ERC on boot. And I > > > /thought/ I read that you still want to adjust the timeouts, though not > > > the > > > same as for consumer drives. > > > > Desktop / consumer drives that support ERC typically ship with it > > disabled, so they behave just like drives that don't support it at all. > > > > So a boot script would enable ERC on drives where it can (and not > > > > already OK), and set long driver timeouts on the rest. > > > > Any drive that claims "raid" compatibility will have ERC enabled by > > default. Typically 7.0 seconds. WD Reds do. Enterprise drives do, and > > have better URE specs, too. > > Good to know. > > > >> If you have consumer grade drives in a raid array, and you don't have > > >> boot scripts or udev rules to deal with timeout mismatch, your *ss is > > >> hanging in the wind. The links in my last msg should help you out. > > > > > > There was some talk of ERC/TLER and md. I'll still have to find or write > > > a > > > script to properly set up timeouts and enable TLER on drives capable of > > > it > > > (that don't come with it enabled by default). > > > > Before I got everything onto proper drives, I just put what I needed > > into rc.local. > [snip] > > > Chris Murphy posted some udev rules that will likely work for you. I > > haven't tried them myself, though. > > > > https://www.marc.info/?l=linux-raid&m=142487508806844&w=3 > > Thanks :) > > > Phil > > -- > > To unsubscribe from this list: send the line "unsubscribe linux-raid" in > > the body of a message to majordomo@xxxxxxxxxxxxxxx > > More majordomo info at http://vger.kernel.org/majordomo-info.html -- Thomas Fjellstrom thomas@xxxxxxxxxxxxx -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
