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Understanding Memory Cards

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Re: Understanding Memory Cards

#21

Post by Marsymars »

3xblah wrote: post #18
verall wrote: post #4

This is an extremely verbose article, but for most people I would highlight the most important things (for SD cards at least): Buy a real brand: people have there own opinions on this, but to me this means Sandisk, Samsung or Verbatim. Had a bad experience with Lexar once but as always ymmv. Buy from a real retailer: this means B&H or Adorama or a not-shady brick and mortar store. Amazon will happily ship you counter…

https://kb.sandisk.com/app/warranty I tried a couple of FAT32 formatted 16GB SanDisk microSD that have a "Lifetime" warranty in an OpenWRT-based router that has a microSD card slot. I managed put them both into unrecoverable "read-only" mode by letting some daemon write to them unconditionally. They were purchased from a large electronics retailer not Amazon. I normally do not use SD cards or USB sticks for non-inter…

That's a good conclusion. You can buy cards that are actually specced for high-endurance workloads, they're usually marketed as either for video capture or industrial applications.

Re: Understanding Memory Cards

#22

Post by duskwuff »

ungzd wrote: post #20

Is there any real difference between SD, SDHC and SDXC, aside "SD uses FAT, SDHC uses FAT32, SDXC uses ExFat"? These cards does not have filesystem controller on it, it's not "FTP over wire", it's block-based storage device. If I format ancient SD from early 2000s with exFat, will it become SDXC? From Wikipedia (marked with "Citation needed"): > The SDHC format, announced in January 2006, brought improvements such as…

SD and SDHC differ in some material ways. SD uses byte-level addressing and is limited to a size of 2 GB. (The spec could theoretically support 4 GB, but is limited by spec to half that, possibly as a hedge against implementation errors.) SDHC uses sector-level addressing, lifting that limit to a theoretical 2 TB.

SDHC and SDXC are identical at a protocol level.

Re: Understanding Memory Cards

#23

Post by gambiting »

Jolter wrote: post #13
goblin89 wrote: post #9

Earlier quoted context omitted.

I haven’t had too many issues ordering from Amazon, but I go through much effort making sure seller is reputable every time and listing was not swapped. Both Adorama and B&H sell on Amazon too, but for photo/video gear I would go to B&H direct.

Amazon will swap in fakes no matter what seller you're using, as long as they're using Amazon's fullfillment services. Search this site, there is like one article a month about it.

Please please please clarify that it's exclusively the problem of Amazon US. As far as I'm aware no other Amazon branch does this.

Re: Understanding Memory Cards

#24

Post by maverick2007 »

jagger27 wrote: post #16
dkdklk wrote: post #12

Earlier quoted context omitted.

Buying from Amazon? You’re likely getting fakes. Genuine SanDisk memory cards are top notch. Sure every brand will have lemons, but if you’re seeing consistently bad “SanDisk” cards.. you are pretty certainly not getting genuine product. Find a reputable supplier (which is absolutely not Amazon)

The general advice for buying off Amazon it to make sure that it's actually coming from Amazon.com, not CheapMemoryAmerica1999.

From what I understand, Amazon comingles their own inventory with third party sellers so although the cards they buy might be legit, you're not necessarily guaranteed to get what they bought vs what CheapMemoryAmerica1999 contributed even if you buy the ones from Amazon

Re: Understanding Memory Cards

#26

Post by opencl »

Const-me wrote: post #7

I wonder which of them, if any, contain a controller chip that does wear leveling? All PC SSDs have them, even very small ones like M.2 2230.

Sandisk released a whitepaper on their SD wear leveling in 2003, not sure if it's changed significantly since then or not: https://web.archive.org/web/20150326122100/http://ugweb.cs.u...

With modern TLC flash any card without wear leveling would fail pretty quickly.

Wear leveling is actually a major problem for applications where power might be suddenly cut, because if it happens while the wear leveling is running then the block allocation table can be corrupted which leaves the whole card unreadable. It's a pretty common complaint among i.e. raspberry pi users who tend to unplug them without shutting down.

Re: Understanding Memory Cards

#27

Post by brudgers »

Const-me wrote: post #7

I wonder which of them, if any, contain a controller chip that does wear leveling? All PC SSDs have them, even very small ones like M.2 2230.

Because I can regularly find 64GB cards at reputable sellers for about $10, I no longer format cards. I shoot until they are full (backing up as I go). When a card is full, I "file" it. Basically, I've started treating memory cards as "digital film". I know they are likely to degrade over the years, but formatting guarantees "degradation" right now in the present. [1] Compared to film, SD cards are cheap. Not zero cost, but @ 40 RAW images per GB, it's only a fraction of a penny per shot. With .jpg it's a fraction of a fraction of a penny.

[1]: It also opens the door for accidental formats.

Re: Understanding Memory Cards

#29

Post by xenadu02 »

ungzd wrote: post #20

Is there any real difference between SD, SDHC and SDXC, aside "SD uses FAT, SDHC uses FAT32, SDXC uses ExFat"? These cards does not have filesystem controller on it, it's not "FTP over wire", it's block-based storage device. If I format ancient SD from early 2000s with exFat, will it become SDXC? From Wikipedia (marked with "Citation needed"): > The SDHC format, announced in January 2006, brought improvements such as…

In theory they support SPI. If you actually try to use it you'll find not only is it dog slow but half the cards out there aren't tested for it anymore and don't work at all or are very flaky.

I would not recommend using SPI mode.

Re: Understanding Memory Cards

#30

Post by jagger27 »

maverick2007 wrote: post #24
jagger27 wrote: post #16

Earlier quoted context omitted.

The general advice for buying off Amazon it to make sure that it's actually coming from Amazon.com, not CheapMemoryAmerica1999.

From what I understand, Amazon comingles their own inventory with third party sellers so although the cards they buy might be legit, you're not necessarily guaranteed to get what they bought vs what CheapMemoryAmerica1999 contributed even if you buy the ones from Amazon

I read that as well. But Amazon does have a good return policy with respect to that, and if you read recent reviews it seems like the problem is mostly over.
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