Hopfgeist

joined 1 year ago
[–] Hopfgeist@feddit.de 1 points 7 months ago (1 children)

Then why do you think manufacturers still list these failure rates (to be sure, it is marked as a limit, not an actual rate)? I'm not being sarcastic or facetious, but genuinely curious. Do you know for certain that it doesn't happen regularly? During a scrub, these are the kinds of errors that are quietly corrected (althouhg the scrub log would list them), as they are during normal operation (also logged).

My theory is that they are being cautious and/or perhaps don't have any high-confidence data that is more recent.

[–] Hopfgeist@feddit.de 0 points 7 months ago

Bit error rates have barely improved since then. So the probability of an error whenr reading a substantial fraction of a disk is now higher than it was in 2013.

But as others have pointed out. RAID is not, and never was, a substitute for a backup. Its purpose is to increase availability. And if that is critical to your enterprise, these things need to be taken into account, and it may turn out that raidz1 with 8 TB disks is fine for your application, or it may not. For private use, I wouldn't fret. but make frequent backups.

This article was not about total disk failure, but about the much more insidious undetected bit error.

[–] Hopfgeist@feddit.de 1 points 7 months ago (3 children)

Let's do the math:

The error-reate of modern hard disks is usually on the order of one undetectable error per 1E15 bits read, see for example the data sheet for the Seagate Exos 7E10. An 8 TB disk contains 6.4E13 (usable) bits, so when reading the whole disk you have roughly a 1 in 16 chance of an unrecoverable read error. Which is ok with zfs if all disks are working. The error-correction will detect and correct it. But during a resilver it can be a big problem.

[–] Hopfgeist@feddit.de 2 points 9 months ago

I also use this, and it works great. Another downside is that when using the free service, others can just use subdomains of your registered domains. You can always deny it, but you have to do it manually. With the premium subscriptions you can prevent that automatically for a number of domains, depending on how much you pay.

[–] Hopfgeist@feddit.de 1 points 10 months ago

To add, unlike "traditional" RAID, ZFS is also a volume manager and can have an arbitrary number of dynamic "partitions" sharing the same storage pool (literally called a "pool" in zfs). It also uses checksumming to determine if data has been corrupted. On redundant setups it will then quietly repair the corrupted parts with the redundant information while reading.

[–] Hopfgeist@feddit.de 1 points 11 months ago

ebay is very international, and is also by far the greatest site for second-hand stuff in most European countries. I normally buy my used drives there.

[–] Hopfgeist@feddit.de 11 points 11 months ago (1 children)

mixing drive models is certainly not going to do any harm

It may, performance-wise, but usually not enough to matter for a small self-hosting servers.

[–] Hopfgeist@feddit.de 1 points 11 months ago* (last edited 11 months ago)

Sure, SCSI disks will show their defective list ("primary defects", as delivered by the factory, and grown defects, accumulated during use), and they all have a couple hundred primary defects. But I don't see why that would affect the reported geometry, given that it is fictional, anway. And all disks have enough spare tracks to accommodate for the defects, and offer the specified full number of total sectors, even for long list of grown defects. Incidentally, all the 4TB disks are still "perfect" in that they have no grown defects.

And yes, ever since LBA, nobody has used sectors and cylinders for anything.

[–] Hopfgeist@feddit.de 7 points 11 months ago* (last edited 11 months ago) (1 children)

I'm not touching that post again. But a small rant about typesetting in lemmy: It seems there is no way whatsoever to put angle brackets in a "code" section. In an overzealous attempt to prevent HTML injection, everything in angle brackets is just removed when posting (although it remains there in preview). In normal text, you can use "<", but not inside "code" segments, where it will be retained verbatim.

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submitted 11 months ago* (last edited 11 months ago) by Hopfgeist@feddit.de to c/selfhosted@lemmy.world
 

I know that for decades now, hard disks don't really reveal their actual internal geometry (which is complicated anyway, since inner cylinders may have fewer sectors than outer cylinders, etc.), and present fictional geometries to satisfy legacy software, but I found it weird anyway.

I have a ZFS raidz2 NAS which originally consisted of 8x2 TB SAS disks and is now in the process of being live-upgraded to 8x4 TB (change disks one by one, resilver, change, resilver, etc ...)

I now have four of the disks replaced, and in NetBSD they all report different geometries. They all report the exact same number of total blocks, so it's not actually an issue, but still strange.

sd0 at scsibus0 target 0 lun 0: <SEAGATE, ST4000NM0023, GE11> disk fixed

sd0: 3726 GB, 330809 cyl, 10 head, 2362 sec, 512 bytes/sect x 7814037168 sectors

sd1 at scsibus0 target 1 lun 0: <SEAGATE, ST4000NM0023, GE11> disk fixed

sd1: 3726 GB, 348145 cyl, 10 head, 2244 sec, 512 bytes/sect x 7814037168 sectors

sd3 at scsibus0 target 3 lun 0: <IBM-B040, ST4000NM0023, BC5P> disk fixed

sd3: 3726 GB, 342419 cyl, 10 head, 2282 sec, 512 bytes/sect x 7814037168 sectors

sd7 at scsibus0 target 7 lun 0: <IBM-B040, ST4000NM0023, BC5P> disk fixed

sd7: 3726 GB, 341874 cyl, 10 head, 2285 sec, 512 bytes/sect x 7814037168 sectors

Two of them are IBM-branded (although they are in fact all Seagate Constellation ES.3), so I might expect slight differences, but even those with the same branding and the same revision present different geometries.

Anyway, probably just a curiosity, it will be interesting to find what the remaining four disks will show.

I might add that the older 2 TB disks (Seagate Constalleation ES, IBM-branded) all show the exact same geometry:

sd2 at scsibus0 target 2 lun 0: <IBM-ESXS, ST32000444SS, BC2D> disk fixed

sd2: 1863 GB, 249000 cyl, 8 head, 1961 sec, 512 bytes/sect x 3907029168 sectors

sd4 at scsibus0 target 4 lun 0: <IBM-ESXS, ST32000444SS, BC2D> disk fixed

sd4: 1863 GB, 249000 cyl, 8 head, 1961 sec, 512 bytes/sect x 3907029168 sectors

sd5 at scsibus0 target 5 lun 0: <IBM-ESXS, ST32000444SS, BC2D> disk fixed

sd5: 1863 GB, 249000 cyl, 8 head, 1961 sec, 512 bytes/sect x 3907029168 sectors

sd6 at scsibus0 target 6 lun 0: <IBM-ESXS, ST32000444SS, BC2D> disk fixed

sd6: 1863 GB, 249000 cyl, 8 head, 1961 sec, 512 bytes/sect x 3907029168 sectors

[–] Hopfgeist@feddit.de 2 points 1 year ago* (last edited 1 year ago)

If you're as paranoid as me about data integrity, SAS drives on a host adapter card in "Initiator Target" (IT) mode with write-cache on the disks disabled is the safest. It will degrade performance when writing many small files concurrently, but not as badly as with SATA drives (that's for spinning disks, of course, not SSD). With a good error-correcting redundant system such as ZFS you can probably get away with enabled write cache in most cases. Until you can't.

[–] Hopfgeist@feddit.de 9 points 1 year ago

RAID is generally a good thing but don’t get complacent, follow the 3-2-1 method

To expand on that: Redundant drive setup and backups serve completely different purposes. The only overlap is in case of a single disk failure, where RAID (or similar) may save the data.

Redundancy is all about reducing downtime in case of single hardware failures. Backups not only protect you from data loss in case of multiple simultaneous failures, but also from accidental deletion. Failures that require restoration of data almost always involve downtime. In short: You always need backups (unless it's strictly a local cache, and easily recreatable), but if you want high availability, redundancy may help.

3-2-1-rule for backups, in case you're unfamiliar: 3 copies of important data, on 2 different media, with 1 off-site.

[–] Hopfgeist@feddit.de 17 points 1 year ago

That's a very narrow-minded view. I thought the same thing when the iPad was new. But I changed my mind.

Sitting on the sofa and watching movies or reading news is a good application, a laptop is too clunky for that, and a phone screen is too small.

Also use as an air-navigation device (not only) light aircraft, and replacement for paper charts in airline operations. There are many legitimate uses where tablets are exactly what you want. If it's not for you, fine.

 

I have two Dell T320 servers, which work great. But I'd like to have some more CPU power, so think about upgrading to the T420. It is almost the same, except that on the T420 main board, which seems to be otherwise the identical PCB, the second CPU socket is actually installed. (In the T320 it's just empty soldering points.) My question is: Is the air baffle the same, or do I need a new one if I swap out the main board? I am aware that I will need a second CPU heatsink.

Thanks.

 

Für alle Piloten, Fluglotsen, Bodenpersonal und alle, die sonst mit Fliegerei zu tun haben oder sich dafür interessieren.

Es ist weniger gedacht für Passagiere oder Planespotter, also nicht in erster Linie eine Foto-Community, obwohl Bilder von ungewöhnlichen Luftfahrzeugen auch gern gesehen sind, wenn es dazu etwas zu sagen gibt.

Es wendet sich eher an die, die selbst fliegen oder das Fliegen ermöglichen.

Sonst: Fragen zu Verfahren, Lufträumen, Prüfungen, Lieblingsflugzeuge, lohnenswerte Flugplätze, ...

r/flying ist zwar wieder offen, aber das war sehr US-zentrisch.

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