By installing an embedded hypervisor/OS on the SD card, you leave all the front-bay disks available for data storage. This is an useful logical and practical separation. Some servers have two RAID1-ed SD slots: if a single SD fails, the system continue to run from the mirror, leaving you the time to replace the failed SD. DDR4 Memory Standard DDR4 Overview. With DDR3 reaching its limits in a world that demands higher performance and increased bandwidth, a new generation of DDR SDRAM has arrived. DDR4 delivers higher performance, higher DIMM capacities, improved data integrity and lower power consumption.

• Purpose Of Memory Slots
• Memory Slot Bad
• Function Of Memory Slots
• Memory Slot Types

What is Micro SD Card?

SD stands for Secure Digital, which is a board developed by SanDisk and Toshiba Corp. The purpose of the SD Card is to improve the use of cards in mobile devices.
In 2001, SD card is mainly for digital cameras, mobile phones, laptops and game consoles from the beginning of development to popular. These memory cards are combined in a small size (32 x 24 x 2.1 mm) and good strength and have become a practical tool for storing different types of data, (from photos and videos to files and applications) in recent years.
In short, the microSD card is just a small external memory.

How does the SD card do?

In most cases, once the Micro SD Card is inserted in your phone, your phone automatically starts scanning the card, pulls out all the information MicroSD Card needs, and immediately stores information in the appropriate location. So that Micro SD Card will start working directly.
If you want to increase the memory of your phone and securely backed up data or pictures, the Micro SD Card is an ideal choice.
Whatever, you need to be careful when deleting your memory card. Ideally, you only need to delete the card when you change your phone. When your phone is actively accessing the memory card, but the connection is disconnected, normally, the card does not know how to handle it. So this may cause your picture can not open correctly, your app crashes. or even for a very sluggish phone, when the phone is completely turned off the SD card can be removed. But many phones have an “Uninstall SD Card” option in their settings, so you can switch them when you need .

As time goes on, more and more big capacity cards are coming out. Mobile cameras increase megapixel size and apps and games getting bigger and bigger. So you do really need a SD card you can get.

1.do some research about the capacity of MicroSD cards supported by your device

You may not know, but not all devices are compatible with SD cards of 128GB, as well as not all devices support different classes and versions of external memories on the market. So, Taking a look at the capacity is very important since you do not want to end up with a card that your device doesn’t support.

2.Buy branded products

Anyway, Brand stand for good quality and reasonable price, Such as,SanDisk, Samsung, Toshiba, Kingston and Toshiba and other famous brands. all of them will not hurt you to pay a little premium. You will reap the rewards. Some of them like SanDisk offer lifelong limited warranty and waterproof and shockproof features, which are very useful if you plan to use your memory card longer and do not want your data corrupted.

Hope these tips can help you to buy a good SD Card!

Further reading

Two card trick

Back in 2004 when the first EOS camera with dual card slots – the professional EOS-1D Mark II – was launched, media cards had a much smaller capacity than nowadays, so having the extra memory accessible without changing cards was important. But there are other benefits to having two card slots in your EOS camera than simply doubling your shooting capacity.

Nowadays, having two card slots in your camera is not so much about the capacity. After all, with cards readily available (and fairly affordable too) offering 128GB, and the current maximum standing at a huge 512GB (as at February 2019), running out of space mid-shoot is the least of our worries.

Instead, having access to two cards gives other options, such as in-camera back-up, the ability to record different file types to each card, and more.

So, how do you access these features?

Which cameras feature two media card slots?

DSLR: EOS-1D Mark II, 1D Mark II N, 1D Mark III, 1D Mark IV, 1Ds Mark II, 1Ds Mark III, 1D X, 1D X Mark II, 1D X Mark III 5D Mark III, 5D Mark IV, 5DS, 5DS R, 7D Mark II

MIRRORLESS: EOS R5, R6

Record func+card/folder sel.

On models such as the EOS-1D X, 1D X Mark II, 5D Mark III, 5DS, 5DS R, 5D Mark IV and 7D Mark II the options to record to the two different card slots has become a complex menu as there are different ways you can set up your camera to use them.

When you enter the SETUP menu – indicated by a wrench or spanner icon – and select Record func+card/folder sel. there are three options: Record func., Record/play and Select folder.

Here's what each option does.

1) Record func.

This function allows you to choose how the images are recorded onto the two cards. The default is standard. There are also options to switch cards, record to both cards or record different formats to each.

Where only one card is fitted in the camera, these settings are overridden.

Standard
This will record to and play back from the card that is set in the record/play menu setting (see 2 below). If there is only one card fitted it is that card; if two are fitted it can default to the first one inserted when the cards are put in if the camera is left on or one card has been removed.

It doesn't matter whether the camera is set to record RAW, JPEG or both – whatever file format the camera is set to record will be to that nominated card.

Auto switch card
(Not available on EOS-1D Mark II/N or 1Ds Mark II).
When this setting is active the camera will record and play back to the nominated card, so long as there is space on the card. If that card becomes full it will seamlessly switch to using the other card. In the days when the cards were a lot smaller this was useful; today with 64GB and 128GB cards available it is rare to fill the main card up.

Purpose Of Memory Slots

Rec. Separately
(Not available on EOS-1D Mark II/N or 1Ds Mark II)
This option is only relevant if you shoot more than one file format, i.e. if you are shooting both RAW and JPEG and have two cards fitted. This allows you to record the RAW files on one card and the JPEG files on the other.

To set which format records to each card, go to the Q screen, then select each card in turn, choosing the preferred file format. This is useful if, for example, you normally shoot JPEG, but like to have a RAW file just in case. One downside with this is that you have two cards to download if you intend to keep everything you shoot.

Rec. to multiple
This is the belt-and-braces approach. This option records whatever file formats you've selected to both cards, giving you two identical copies of each file, if you then download both cards. On the plus side, it gives reassurance if you're concerned that a card might fail. However, you need a good stock of media cards and time on your hands to manage the file duplication successfully.

2) Record/play

Selecting this menu item allows you to specify which is the main card where two cards are fitted. Exactly what options appear will depend what the first menu item – Record func. – (1 above) is set to.

If Record func. is set to Standard or Auto switch card, then you'll just have the option of the two cards. If set to Rec.separately or Rec. to multiple, then it gives the options of which card you want to play back from.

Memory Slot Bad

3) Select Folder

Here you can create your own folders in which to store your images on the media card, rather than allowing the camera to do this automatically. When you enter this menu item you will see a list of folders currently on the card. The active folder is highlighted and the camera will allocate the next folder in sequence. To select the folder you want to record to, highlight the folder and press set.

This makes sense if you download your images manually (e.g. with a card reader, by dragging them from the card to where you want them on the computer). If you let one of your programs download automatically this information often becomes hidden or lost altogether as most programs utilise date information for filing.

Shots remaining count

When Rec. separately or Rec. to multiple is set, the number of possible shots available will be from the card with the lower capacity. When either of the cards becomes full, 'Card full' wil be displayed and no further shooting is possible.

Function Of Memory Slots

To use up the capacity on the card which is not yet full, switch the recording method to Standard, select the relevant card and continue shooting.

Which camera accepts which card types?

Memory Slot Types