Non Recoverable Error Rate
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is the best choice, ever [1]. There are cases where RAID0 is mathematically proven more reliable than RAID5 [2]. RAID5 should never unrecoverable read error rate be used for anything where you value keeping your data. I am not
Unrecoverable Read Error Ure
exaggerating when I say that very often, your data is safer on a single hard drive than it is on a raid 5 ure calculator RAID5 array. Please let that sink in.The problem is that once a drive fails, during the rebuild, if any of the surviving drives experience an unrecoverable read error (URE), the entire array will fail. what happens if the array experiences a ure during the rebuild process? On consumer-grade SATA drives that have a URE rate of 1 in 10^14, that means if the data on the surviving drives totals 12TB, the probability of the array failing rebuild is close to 100%. Enterprise SAS drives are typically rated 1 URE in 10^15, so you improve your chances ten-fold. Still an avoidable risk.RAID6 suffers from the same fundamental flaw as RAID5, but the probability of complete array
Why Not To Use Raid 5
failure is pushed back one level, making RAID6 with enterprise SAS drives possibly acceptable in some cases, for now (until hard drive capacities get larger).I no longer use parity RAID. Always RAID10 [3]. If a customer insists on RAID5, I tell them they can hire someone else, and I am prepared to walk away.I haven't even touched on the ridiculous cases where it takes RAID5 arrays weeks or months to rebuild, while an entire company limps inefficiently along. When productivity suffers company-wide, the decision makers wish they had paid the tiny price for a few extra disks to do RAID10.In the article, he has 12x 4TB drives. Once two drives failed, assuming he is using enterprise drives (Dell calls them "near-line SAS", just an enterprise SATA), there is a 33% chance the entire array fails if he tries to rebuild. If the drives are plain SATA, there is almost no chance the array completes a rebuild.[1] http://www.smbitjournal.com/2012/11/choosing-a-raid-level-by...[2] http://www.smbitjournal.com/2012/05/when-no-redundancy-is-mo...[3] http://www.smbitjournal.com/2012/11/one-big-raid-10-a-new-st... Twirrim 770 days ago Note that the 10^14 figure is only what the HDD mfgs publish, and it has been the same for something like a decade. It's a nice, safe, conservative figure that seems impressively high to IT Directors and accountants, and yet it'
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Raid 6 Ure
"non Recoverable Error Rate" Specification Started by mattsaccount, February 28, 2004 3 posts in this topic mattsaccount 0 Member Member 0 32 posts Posted February 28, 2004 · Report post Hello, I apologize if this has been asked before. https://news.ycombinator.com/item?id=8306499 To what, precisely, is this specification referring? Some manufacturers claim "< 1 bit in 10^15". 10^15 bits is 116415 gigabytes if my math is right. Surely hard drives make more mistakes than this? Is this related to MTBF, in that they test, say, 1000 hard disks when they are new, and observe the total number of errors after reading/writing this many bits? Share this post Link to post Share on other sites blakerwry 0 StorageReview Patron Patron 0 http://forums.storagereview.com/index.php?/topic/14254-non-recoverable-error-rate-specification/ 4840 posts Location:Kansas City USA Posted February 28, 2004 · Report post A non-recoverable error is when a hard drive cannot reliably read a sector AND cannot determine the correct value through ECC or retries. The non-recoverable error rate is the rate at which these errors occur during normal operation. This would probably result in your file system marking this section of the disk as a bad block. If the sector is written to and cannot be written to successfully then that sector will be remapped. Obviously if your file system marked the sector(or block rather) as bad it will not be written to until you reformat. Share this post Link to post Share on other sites blakerwry 0 StorageReview Patron Patron 0 4840 posts Location:Kansas City USA Posted February 28, 2004 · Report post hmm.. that would be neat to have an "odometer" to tell how much data really does get read on the average hard drive. Share this post Link to post Share on other sites Create an account or sign in to comment You need to be a member in order to leave a comment Create an account Sign up for a new account in our community. It's easy! Register a new account Sign in Already have an account? Sign in here. Sign In Now Sign in to follow this Followers 0 Go To Topic Listing Hard Disk Drives (HDD) All Activit
»reddit.comzfscommentsWant to join? Log in or sign up in seconds.|Englishlimit my search to /r/zfsuse the following search parameters to narrow your results:subreddit:subredditfind submissions in "subreddit"author:usernamefind submissions by "username"site:example.comfind https://www.reddit.com/r/zfs/comments/3gpkm9/statistics_on_realworld_unrecoverable_read_error/ submissions from "example.com"url:textsearch for "text" in urlselftext:textsearch for "text" in self post contentsself:yes (or self:no)include https://forums.freenas.org/index.php?threads/10-15-wd-red-pro.23261/ (or exclude) self postsnsfw:yes (or nsfw:no)include (or exclude) results marked as NSFWe.g. subreddit:aww site:imgur.com dogsee error rate the search faq for details.advanced search: by author, subreddit...this post was submitted on 12 Aug 20153 points (72% upvoted)shortlink: remember mereset passwordloginSubmit a new linkSubmit a new text postzfssubscribeunsubscribe1,539 readers~3 users here nowcreated by bbatsella community unrecoverable read error for 6 yearsmessage the moderatorsMODERATORSbbatsellerimar77about moderation team »discussions in /r/zfs<>X9 points · 21 comments Necessity of ZIL and L2ARC for all flash ZFS pool?6 points · 11 comments Does "zpool create" create a filesystem? Is it special somehow?4 points · 5 comments "Manually" (from script) take daily snapshot for a single dataset using Sanoid?4 points · 19 comments Interesting design - High Availability Storage On Dell PowerEdge and HP ProLiant0 points · 43 comments combine zfs pools using mhddfs or aufs?9 points · 2 comments OpenZFS Developer Summit 2016 Videos Now Online3 points Review/testing of beadm/zfs_facts/zpool_facts Ansible modules needed3 points · 7 comments Is ther
Points: 6 are the new Western Digital WD4001FFSX the only or Red Pro the only one with the non-recoverable read error rate better than the others at < 10^15 bits? for what I read the disks with the < 10^14 bits the 100% considered to be sure to find an non-recoverable read error rate if for 10 TB (0.01 PB), so for instance you can't have a 4TB - 10 disk raidZ-2 because it would be totally useless, even a raidZ-3 for example, if 10 disk of 4TB it would be a total of 40 TB raw storage (29 of usable storage) so when the 10 TB mark is read is almost a 100% chance of encountering a hard disk error, the failed cause the raid to rebuild and we can then expect another disk failure because all of the remaining 9 drives will have to be need read (36 TB) ,hitting another 10 TB of data, and another hard disk error, now for the RaidZ-2 there is non protecction (2 failure disk), rebuilding and reading the another 8 disk (32 TB) it sure will hit again the 10 TB mark, therefore the second rebuild is very likely to fail. I don't remember the exact page, but the title was SAS vs. SATA from enterprisestorageforum.com ¿It's all this true? ¿What do you think guys from this new WD Red Pro HDD? I am not an expert so I seek advice from more experienced in this forum Thanks and kind regards to all EDIT. found the page SAS VS SATA Last edited: Sep 3, 2014 ALFA, Sep 3, 2014 #1 cyberjock Moderator Moderator Joined: Mar 25, 2012 Messages: 19,103 Thanks Received: 1,640 Trophy Points: 161 This is statistics and engineering notations for things, so you do need to keep things on context. Yes, if you have a 10TB pool the statistics show that you are almost 100% likely to hit a URE. But, those engineering numbers are nothing more than a bunch of secret magic and they are also "rated" values. That is, your drive might be 10^30 or 10^16. As long as the drive isn't having UREs at a rate that is higher than 10^15 then everything is considered 'acceptable'. To be honest, thos