If there's just a single failed bit in the sector, the data can be reconstructed from the CRC. So anyway, the low URE rate of your drives may in fact be due to premature SCSI resets of drives on your pool; after the reset, many times the drive can One of the purposes of SMART is to alert you to the existence of abundant UREs that represent bits that can no longer be written to disk when your sector remap See:http://forum.synology.com/wiki/index.ph ... navigate here
Also as somebody else has also mentioned. permalinkembedsaveparentgive gold[–]mercenary_sysadmin 1 point2 points3 points 1 year ago(5 children) I would rather base decisions on studies than personal anekdote, that's the reason for this topic. When it comes to reliability, enterprise grade disks are generally at least one order of magnitude more reliable than their nonenterprise counterparts. 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
Apparent mathematical reasoning: 1 URE per 10^14 bytes / 8 HDD per array = 1 URE per 12.5 TB read from the 8-drive array. Everyone who loves science is here! This breaks down if we mix RAID types or radically swing IOPS capabilities and such, but seems to have worked OK as a rule-of-thumb for the past several years for me.
Trevor is ignoring the economics. They could be a sector gone bad. I saw by far the most errors with WD Green and Seagate Barracuda drives, which I no longer use. Ure Definition The extra bits themselves take up space on the HDD, but allow higher recording densities to be employed without causing uncorrectable errors, resulting in much larger storage capacity. For example, a
As far as I know, the ZFS block checksum is a hash (sha256) which can detect corruption but has no ability to repair damaged blocks. What Happens If The Array Experiences A Ure During The Rebuild Process? Top roadkill401 Rookie Posts: 38 Joined: Sun Sep 11, 2011 11:27 pm Re: This BS called URE Quote Postby roadkill401 » Mon Jan 26, 2015 10:50 pm But here is where Part 4: Cosmic Acoustics Struggles with the Continuum – Part 7 Interview with a Physicist: David Hestenes Why Supersymmetry? What I'm not OK with is that people read these spec sheets and then claim RAID5 is dead and scare everybody with this.
Because it doesn't seem to reflect real-life in any way. Zfs Ure The data is eminently recoverable in such a case, and you'll generally see UREs from these drives -- assuming average sub-2k writes -- once your sector remap area is full. Enterprise SSD error rates are 10^17 bits or an error every 12.5PB. Every article about URE's starting with this one: http://www.zdnet.com/article/why-raid-5-stops-working-in-2009/ Scares you with the 12.5 TB number.
Increasing drive capacities and large RAID 5 instances have led to an increasing inability to successfully rebuild a RAID set after a drive failure and occurrence of an unrecoverable sector on There are better forms of erasure coding for long-term data reliability. Unrecoverable Read Error Ure Therefore, for consumer NAS builds I think it's perfectly reasonable to build RAID5 or RAIDZ arrays and sleep safe, as long as you don't put too many drives in a single Ure Hard Drive [email protected]:~# zpool iostat -v storage capacity operations bandwidth pool alloc free read write read write ------------------------------ ----- ----- ----- ----- ----- ----- storage 36.0T 50.8T 819 42 99.2M 3.22M raidz2 7.13T
permalinkembedsaveparentgive gold[–]SirMaster 0 points1 point2 points 1 year ago*(15 children) Assuming two vdevs in a pool, if one is half the size of the other it will receive only one-third of the writes. check over here I can imagine that it happens. I've often wondered if there wouldn't be a reliable way to simulate this behavior in software. p?lang=enu Post Reply Print view Search Advanced search 9 posts • Page 1 of 1 roadkill401 Rookie Posts: 38 Joined: Sun Sep 11, 2011 11:27 pm This BS called URE Quote Unrecoverable Read Error Nero
EDIT: I think I must clarify that I'm mainly interested in a risk perspective for the 'average home user' who wants to build their own NAS solution, not a mission-critical corporate When blocks of flash or sectors of a disk are permanently unreadable (one type of URE) then the sector is marked bad and a "spare" sector is mapped in. permalinkembedsaveparentgive gold[–]txgsync 0 points1 point2 points 1 year ago(1 child) as far as I am aware with disk failures ZFS has no more ability to recover data after drive failure than its equivalent his comment is here Hardened SSD error rates are 10^18 bits or an error every 125PB.
On the other hand, OpenZFS uses version 28 as the base, and if any new features are enabled the version number is bumped to "5000" with feature flags for specific features Raid 5 Ure Calculator When a disk in a RAID-5 array fails and is replaced, all the data on other drives in the array must be read to reconstruct the data from the failed drive. I stand corrected regarding the URE rating of those drives.I did a bit of searching - it is the Western Digital Se drives that have the atypical URE rating of <10
According to you, we are simply doomed by your calculation in reading any disks you are going to get a read error eventually and sooner than you really would hope for. Data in the hard drive array would be much, much safer for the same money. Scott Lowe talks about UREs and how you can avoid falling victim to this silent threat. Raid 10 Ure DSHR DSHR in ANWR My Projects LOCKSS (a trademark of Stanford University) CLOCKSS LOCKSS system has permission to collect, preserve, and serve this Archival Unit.
DSHR DSHR in ANWR My Projects LOCKSS (a trademark of Stanford University) CLOCKSS LOCKSS system has permission to collect, preserve, and serve this Archival Unit. i.e. Using just the URE statistic provided by drive manufacturers, drives in this RAID 5 array with a one URE in 10^14 rating have a roughly 38.1% chance of failing to successfully weblink It is simply gone.