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Everything I Know About SSDs

kcall.co.uk

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Re: Everything I Know About SSDs

#151

Post by mehrdadn »

wtallis wrote: post #150
mehrdadn wrote: post #135

Earlier quoted context omitted.

Low LBAs are outside rather than inside?? I had no idea.

It stands to reason. The low LBAs get filled first and used most. The outside of the disk is where the linear speed is fastest, and it's closest to where the heads park.

Yeah I understood that immediately after I read it, but it's not how typical optical discs work, and I'd just assumed they work the same way until now. Hadn't really thought about it before.

What I find a bit bizarre though that some defragmenters have an option to move files to the end of the drive. Wouldn't you want to move files to the beginning in that case?

Re: Everything I Know About SSDs

#152

Post by SlowRobotAhead »

wtallis wrote: post #99
SlowRobotAhead wrote: post #95

Earlier quoted context omitted.

PERC HP740 controllers in Dell servers iirc are hardware raid for the flex port U.2 and backplane pcie nvme drives.

Yes, that's one of the cards that use Broadcom/Avago/LSI "tri-mode" HBA chips (SAS3508 in this case). It comes with the somewhat awkward caveat of making your NVMe devices look to the host like they're SCSI drives, and constraining you to 8 lanes of PCIe uplink for however many drives you have behind the controller. Marvell has a more interesting NVMe RAID chip that is fairly transparent to the host, in that it makes…

So stay under 8 physical NVME and it should be fine?

Re: Everything I Know About SSDs

#153

Post by exikyut »

StavrosK wrote: post #129

Mirror: http://archive.is/K9SFI

archive.is links have not been working for me for a while now. I wasn't sure if something was wrong with the site or what, but seeing this link posted here convinced me to do a bit of digging.

I have news: 1.1.1.1, aka CloudFlare's DNS, resolves archive.is to 127.0.0.5.

Live proof: https://digwebinterface.com/?hostnames=archive.is&useresolve...

Archived proof: http://archive.is/utJfW

Of course the moment I changed 1.1.1.1 to 8.8.8.8 in resolv.conf I was able to access the site again.

Re: Everything I Know About SSDs

#154

Post by leesalminen »

exikyut wrote: post #153
StavrosK wrote: post #129

Mirror: http://archive.is/K9SFI

archive.is links have not been working for me for a while now. I wasn't sure if something was wrong with the site or what, but seeing this link posted here convinced me to do a bit of digging. I have news: 1.1.1.1, aka CloudFlare's DNS, resolves archive.is to 127.0.0.5. Live proof: https://digwebinterface.com/?hostnames=archive.is&useresolve... Archived proof: http://archive.is/utJfW Of course the moment I changed 1.…

1.1.1.1 has been acting up for me recently as well but haven’t had a chance to investigate. Glad to hear it’s not just me

Re: Everything I Know About SSDs

#155

Post by uj8efdkjfdshf »

exikyut wrote: post #153
StavrosK wrote: post #129

Mirror: http://archive.is/K9SFI

archive.is links have not been working for me for a while now. I wasn't sure if something was wrong with the site or what, but seeing this link posted here convinced me to do a bit of digging. I have news: 1.1.1.1, aka CloudFlare's DNS, resolves archive.is to 127.0.0.5. Live proof: https://digwebinterface.com/?hostnames=archive.is&useresolve... Archived proof: http://archive.is/utJfW Of course the moment I changed 1.…

It's over a disagreement between Cloudflare and the owner of Archive.is regarding the forwarding of EDNS metadata.

See here: https://news.ycombinator.com/item?id=19828317

Re: Everything I Know About SSDs

#156

Post by stavros »

exikyut wrote: post #153
StavrosK wrote: post #129

Mirror: http://archive.is/K9SFI

archive.is links have not been working for me for a while now. I wasn't sure if something was wrong with the site or what, but seeing this link posted here convinced me to do a bit of digging. I have news: 1.1.1.1, aka CloudFlare's DNS, resolves archive.is to 127.0.0.5. Live proof: https://digwebinterface.com/?hostnames=archive.is&useresolve... Archived proof: http://archive.is/utJfW Of course the moment I changed 1.…

Yes, there was some discussion a while ago here, CloudFlare says archive.is won't reply with the correct DNS to them and the author of archive.is says CloudFlare isn't passing the correct information to his server, and he refuses to change it.

I don't remember details, I'm afraid, but it is an unfortunate situation.

Re: Everything I Know About SSDs

#157

Post by [deleted] »

exikyut wrote: post #153
StavrosK wrote: post #129

Mirror: http://archive.is/K9SFI

archive.is links have not been working for me for a while now. I wasn't sure if something was wrong with the site or what, but seeing this link posted here convinced me to do a bit of digging. I have news: 1.1.1.1, aka CloudFlare's DNS, resolves archive.is to 127.0.0.5. Live proof: https://digwebinterface.com/?hostnames=archive.is&useresolve... Archived proof: http://archive.is/utJfW Of course the moment I changed 1.…

[deleted]

Re: Everything I Know About SSDs

#158

Post by corford »

exikyut wrote: post #153
StavrosK wrote: post #129

Mirror: http://archive.is/K9SFI

archive.is links have not been working for me for a while now. I wasn't sure if something was wrong with the site or what, but seeing this link posted here convinced me to do a bit of digging. I have news: 1.1.1.1, aka CloudFlare's DNS, resolves archive.is to 127.0.0.5. Live proof: https://digwebinterface.com/?hostnames=archive.is&useresolve... Archived proof: http://archive.is/utJfW Of course the moment I changed 1.…

Nice find. archive.is stopped working for me recently and I just assumed it had disappeared. Now I know its because I happened to change my router's resolver from 8.8.8.8 to 1.1.1.1.

Edit: Would be cool if archive.is implemented this comment https://news.ycombinator.com/item?id=19832572 (from previous HN discussion on this)

Re: Everything I Know About SSDs

#159

Post by namibj »

notacoward wrote: post #2

The part about filesystems is slightly incorrect. > The way the file system handles this is incompatible with the workings of NAND flash. That's true of most conventional filesystems, but log-structured filesystems are much more flash-friendly. That's why there has been a resurgence of interest in them, and also why a typical flash translation layer bears a striking resemblance to a log-structured FS. There are also…

I briefly searched for a source of (mostly) FTL-less microSD cards (I'd be fine with them doing wear leveling-related remapping of whole blocks, as long as it's power-loss-safe, but I don't want them to expend any effort on emulating 512/4k random write capability).

I didn't find anything but bunnie's blog entry[0] on hacking/re-flashing the firmware on the card's controller.

Due to how important it is to have a good FTL, and the pretty much native suitability of log-structured data formats, like those based on RocksDB or InfluxDB (both not unlikely for data handled and stored on RPi-like SBCs), it'd be much better for reliability and performance reasons to let these LSM engines deal with NAND flash's block erase/sector write/sector read behavior.

[0]: https://www.bunniestudios.com/blog/?p=3554

Re: Everything I Know About SSDs

#160

Post by wtallis »

SlowRobotAhead wrote: post #152
wtallis wrote: post #99

Earlier quoted context omitted.

Yes, that's one of the cards that use Broadcom/Avago/LSI "tri-mode" HBA chips (SAS3508 in this case). It comes with the somewhat awkward caveat of making your NVMe devices look to the host like they're SCSI drives, and constraining you to 8 lanes of PCIe uplink for however many drives you have behind the controller. Marvell has a more interesting NVMe RAID chip that is fairly transparent to the host, in that it makes…

So stay under 8 physical NVME and it should be fine?

A typical NVMe SSD has a four-lane PCIe link, or 2+2 for some enterprise drives operating in dual-port mode. So it usually only takes 2 or 3 drives to saturate an 8-lane bottleneck. Putting 8 NVMe SSDs behind a PCIe x8 controller would be a severe bottleneck for sequential transfers and usually also for random reads.
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