There's been a lot of talk lately about our position on removable storage and removable batteries in smartphones. Most of the discussion has centered around what we've said in podcasts or alluded to in reviews, so we figured it's a good time to have the complete discussion in one central location.

Let's get through the basics first:

All else being equal, removable storage and user replaceable batteries aren't inherently bad things. In fact, they can offer major benefits to end users. 

The key phrase however is "all else being equal". This is where the tradeoff comes in. On the battery front, the tradeoff is very similar to what we saw happen in notebooks. The move away from removable batteries allows for better use of internal volume, which in turn increases the size of battery you can include at the same device size. There are potential build quality benefits here as well since the manufacturer doesn't need to deal with building a solid feeling removable door/back of some sort. That's not to say that unibody designs inherently feel better, it's just that they can be. The tradeoff for removable vs. integrated battery is one of battery capacity/battery life on a single charge. Would you rather have a longer lasting battery or a shorter one with the ability the swap out batteries? The bulk of the market seems to prefer the former, which is what we saw in notebooks as well (hence the transition away from removable batteries in notebooks). This isn't to say that some users don't prefer having a removable battery and are fine carrying multiple batteries, it's just that the trend has been away from that and a big part of the trend is set based on usage models observed by the manufacturers. Note that we also don't penalize manufacturers for choosing one way or another in our reviews.

The tradeoffs are simple with an internal battery, the OEM doesn't need to include a rigid support structure on the battery to prevent bending, and doesn't need to replicate complicated battery protection circuitry, and can play with alternative 3D structures (so called stacked batteries) for the battery and mainboard as well. Personally, I'd rather have something that lasts longer on a single charge and makes better use of internal volume as that offers the best form factor/battery life tradeoff (not to mention that I'm unlikely to carry a stack of charged batteries with me). It took a while for this to sink in, but Brian's recommendation to charge opportunistically finally clicked with me. I used to delay charging my smartphone battery until it dropped below a certain level and I absolutely needed to, but plugging in opportunistically is a change I've made lately that really makes a lot of sense to me now.

The argument against removable storage is a similar one. There's the question of where to put the microSD card slot, and if you stick it behind a removable door you do run into the same potential tradeoff vs. build quality and usable volume for things like an integrated battery. I suspect this is why it's so common to see microSD card slots used on devices that also have removable batteries - once you make the tradeoff, it makes sense to exploit it as much as possible.

There's more to discuss when it comes to microSD storage however. First there's the OS integration discussion. Google's official stance on this appears to be that multiple storage volumes that are user managed is confusing to the end user. It's important to note that this is an argument targeted at improving mainstream usage. Here Google (like Apple), is trying to avoid the whole C-drive vs. D-drive confusion that exists within the traditional PC market. In fact, if you pay attention, a lot of the decisions driving these new mobile platforms are motivated by a desire to correct "mistakes" or remove painpoints from the traditional PC user experience. There are of course software workarounds to combining multiple types of storage into a single volume, but you only have to look at the issues with SSD caching on the PC to see what doing so across performance boundaries can do to things. Apple and Google have all officially settled on a single storage device exposed as a single pool of storage, so anything above and beyond that requires 3rd party OEM intervention.

The physical impact as well as the lack of sanctioned OS support are what will keep microSD out of a lot of flagship devices. 

In the Android space, OEMs use microSD card slots as a way to differentiate - which is one of the things that makes Android so popular globally, the ability to target across usage models. The NAND inside your smarpthone/tablet and in your microSD card is built similarly, however internal NAND should be higher endurance/more reliable as any unexpected failures here will cause a device RMA, whereas microSD card failure is a much smaller exchange. The key word here is should, as I'm sure there are tradeoffs/cost optimizations made on this front as well. 

The performance discussion also can't be ignored. Remember that a single NAND die isn't particularly fast, it's the parallel access of multiple NAND die that gives us good performance. Here you're just going to be space limited in a microSD card. Internal NAND should also be better optimized for random IO performance (that should word again), although we've definitely seen a broad spectrum of implementation in Android smartphones (thankfully it is getting better). The best SoC vendors will actually integrate proper SSD/NAND controllers into their SoCs, which can provide a huge performance/endurance advantage over any external controller. Remember the early days of SSDs on the PC? The controllers that get stuffed into microSD cards, USB sticks, etc... are going to be even worse. If you're relying on microSD cards for storage, try to keep accesses to large block sequentials. Avoid filling the drive with small files and you should be ok.

I fully accept that large file, slow access storage can work on microSD cards. Things like movies or music that are streamed at a constant, and relatively low datarate are about the only things you'll want to stick on these devices (again presuming you have good backups elsewhere).

I feel like a lot of the demand for microSD support stems from the fact that internal storage capacity was viewed as a way to cost optimize the platform as well as drive margins up on upgrades. Until recently, IO performance measurement wasn't much of a thing in mobile. You'd see complaints about display, but OEMs are always looking for areas to save cost - if users aren't going to complain about the quality/size/speed of internal storage, why not sacrifice a bit there and placate by including a microSD card slot? Unfortunately the problem with that solution is the OEM is off the hook for providing the best internal storage option, and you end up with a device that just has mediocre storage across the board.

What we really need to see here are 32/64/128GB configurations, with a rational increase in price between steps. Remember high-end MLC NAND pricing is down below $0.80/GB, even if you assume a healthy margin for the OEM we're talking about ~$50 per 32GB upgrade for high-speed, high-endurance internal NAND. Sacrifice on margin a bit and the pricing can easily be $25 - $35 per 32GB upgrade.

Ultimately this is where the position comes from. MicroSD cards themselves represent a performance/endurance tradeoff, there is potentially a physical tradeoff (nerfing a unibody design, and once you go down that path you can also lose internal volume for battery use) and without Google's support we'll never see them used in flagship Nexus devices. There's nothing inherently wrong with the use of microSD as an external storage option, but by and large that ship has sailed. Manufacturers tend to make design decisions around what they believe will sell, and for many the requirement for removable storage just isn't high up on the list. Similar to our position on removable batteries, devices aren't penalized in our reviews for having/not-having a removable microSD card slot.

Once you start looking at it through the lens of a manufacturer trying to balance build quality, internal volume optimization and the need for external storage, it becomes a simpler decision to ditch the slot. Particularly on mobile devices where some sort of a cloud connection is implied, leveraging the network for mass storage makes sense. This brings up a separate discussion about mobile network operators and usage based billing, but the solution there is operator revolution.

I'm personally more interested in seeing the price of internal storage decrease, and the performance increase. We stand to gain a lot more from advocating that manufacturers move to higher capacities at lower price points and to start taking random IO performance more seriously.



View All Comments

  • zyky - Saturday, November 30, 2013 - link

    It's sad to see mainstream consumers limiting options for power users because they're willing to settle for these things. Just like 1366x768 laptops dominating the marketplace, these "good enough for watching movies" products are designed to a price only. These non-in-the-field replacable battery phones are not yielding any significant battery life advantage and in most phones, do not take up any more space with the battery than removable battery phones do. And even if they were able to squeeze in a 25% larger battery, that's still a far cry from the practically limitless supply one gets with replaceable batteries. More importantly, batteries wear out, and run-time shortens over time. Pretty soon that 125% battery is lasting 1/2 as long, and a $5 30second fix wont solve it. Not only do batteries wear out, but so does flash memory. Why would I want to worry about constantly rewriting to internal flash memory over and over and slowly killing the phone, when I could be saving files to easy-to-replace micro SD cards instead. The same micro SD cards that I can ready in many other devices and not have to rely on the phone even having power to access, or worry about losing access to important documents if other parts of the phone died.

    I don't buy items to throw in a land fill in 6 months, I'd rather buy quality products that will last me a lifetime. I don't want to "use it up, and replace it." And I'm sure I'm not alone in the willingness to pay extra for some insured longevity and durability.

    Then again, I'm also part of the minority that insists on a physical keyboard too, I may never be able to buy a new phone again the way things are going.

    With the current stance on phones w/o batteries or micro SD slots, the continual reinforcement that current SSD NAND wear is good enough, even with tri-level-cell packages, and even the most recent statement where they thought the WD Black^2 would have been better off as a caching hybrid drive rather than discrete segmented areas Anandtech has pretty much jumped the shark for enthusiasts and power users. Walled garden Apple and Microsoft sycophants can come here to see the latest gotta-gave gadget every month to replace their phone with a larger screen every month instead.
  • hrrmph - Sunday, December 1, 2013 - link

    Want Micro-SDXC and removable battery in a 4" class device?

    Unlocked Blackberry Z10 direct from the Blackberry USA store. Today only. $200.
  • nitram_tpr - Monday, December 2, 2013 - link

    I am currently using a Galaxy S2. The life of the original battery was pretty poor so I got the official extended battery and now I am more than happy with the life :) I have a 32gig SD card full of MP3s, books and magazines. I (originally) got this phone because of the options it afforded me.
    I also have a Transformer Prime tablet, it has served me well since I got it, I use it every day. One of the things I love about it is the fact it has so much expandable memory capabilities. I have 16gig in the tablet and 32 gig in the dock. I'm waiting for the new Nexus 10 to see if I will upgrade. If it doesn't come with a 128gig version then I'm gonna stick with the Prime. 64gig for my tablet is just about enough for me, I do like having the card options though. I have a large book / magazine library and I watch one or two movies / tv episodes on my daily commute by train. If I had a tablet with limited storage it would be extremely tiresome having to change files on a regular basis.
    Cloud storage is all well and good if you have access to a fast home broadband connection or can afford to have a 4G connection with a large allowance. I have neither, I live in a rural location and am lucky if I get 2meg download speeds on my ADSL and just about get a mobile signal so a device with expandable storage is essential for me.
  • Steven JW FCK - Monday, December 2, 2013 - link

    "Similar to our position on removable batteries, devices aren't penalized in our reviews for having/not-having a removable microSD card slot."

    Ok, I accept that, but you must accept that you aren't praising this feature as a benefit and a *USEFUL* feature to many. You (Anandtech) are taking a very clouded view upon what I see as a deal breaker in picking my next phone and shunning it as a token feature, that's not worth your time of day.

    You may well be more interested in seeing the price of internal storage decrease, but in the meantime, a lot of people are suffering from *INFLATION* and the *RISING COSTS OF LIVING,* so day dreaming about NAND memory prices all of a sudden falling is a fantasy you need to GET OVER. I mean Apple charge in the UK nearly £100 for 16GB memory, the most of any manufacturer, and they will do all they can to preserve these 1000%+ profit margins so long as you keep telling people they're worth it. If you want to pay £100 for 16GB of memory, you can, but I'll protest those extortionate costs and ridiculous mark up in my option NOT TO BUY THEIR PRODUCTS, thank you.
  • sayash - Tuesday, December 3, 2013 - link

    Nexus 5 review? Are you paid by apple to specifically delay it? Reply
  • julandorid - Tuesday, December 3, 2013 - link

    Hahaha. The phone is too good to be reviewed by Anand. Probably they cannot find any flaw to bitch around :D Reply
  • Arbie - Tuesday, December 3, 2013 - link

    I bought a Nokia 520 ($150 unlocked) BECAUSE it had micro-SD. So in one tiny device I have all the phone necessities, minor alarm / calculator etc apps, AND a personal entertainment system. I have several 32GB chips and can swap in movies, tv shows, a large music collection, audiobooks, and ebooks. It also has a snap-in battery, so I have the option of carrying a spare on long trips AND have no concern over when the original no longer takes a charge.

    --> Anandtech tells me that none of these things actually matter.

    The phone case is perfectly solid, and thin enough for me.

    --> Anandtech tells me that I should demand more in build quality and form factor.

    Go figure.
  • BoloMKXXVIII - Tuesday, December 3, 2013 - link

    I can only go by my own experience. I have owned 6 cell phones. I have had to replace the batteries in every one of them. I tend to keep my phones longer than most do, and the phones always seem to last an entire day for the first year or so, then they need to be charged part way through the day. I travel a lot also. Carrying a spare battery "just in case" is nice also. Fading batteries is not brand specific. I have owned Motorolas, HTCs, and a Samsung. I will consider buying a phone without a microSD card slot (if it has 128 GB of storage) but until they stop making cell phones without removable batteries I will always buy cell phones that have replacable batteries. Even if I have to go gray market "world" phones. Reply
  • bhima - Tuesday, December 3, 2013 - link

    I think the battery argument is flawed as well. It is true that you can have potentially better battery life in a fully integrated system, but I don't believe its necessarily that big of a deal to scrap removable batteries all-together. Take the Samsung Note 3... for having a ridiculously large, bright screen it gets pretty dang good battery life. Easily enough to get you through a full day. I don't believe having better overall battery performance than say the Note 3 is worth the trade-off of basically having to landfill your non-user replaceable phone in a few years just because it won't hold a charge anymore.

    Anandtech was ahead of the curve when they posited years ago that off-contract services would gain more traction and that would lead to people purchasing phones out-right instead of running a subsidized contract. I agree with that, and with that I believe people who buy their phones outright are LESS likely to want to replace them in 2 years, just like most people don't replace their computers every 2 years. Therefore, not having a removeable battery basically guarantees you will have to, even if you don't want to.
  • dynamited - Tuesday, December 3, 2013 - link

    Yup, that is it, no battery replacement and you're guaranteed disposable phones and how much quality goes into anything inherently disposable and obsoletable every two years? Batteries have a cycle rate, of which the percentage to full charge is less every time. Sorry physics.

    Someone else wrote here, "I really find this article disappointing. I feel as though the authors are so far into their viewpoint that they're incapable of evaluating the other side fairly." I feel the same way. Anand and company are so embedded with apple in their personal life choices they are incapable of an unbiased opinion. Too bad. BTW, where's the Nexus5 review?

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