Editing SD card (section)

== Performance ratings ==
{| class="wikitable" style="float:right; text-align:center;"
|+Comparison of Application Performance Class ratings<ref>{{Cite web |date=2020-12-11 |title=Application Performance Class {{!}} SD Association |url=https://www.sdcard.org/developers/sd-standard-overview/application-performance-class/ |access-date=2025-01-07 |website=www.sdcard.org |language=en-US |archive-date=3 November 2021 |archive-url=https://web.archive.org/web/20211103014547/https://www.sdcard.org/developers/sd-standard-overview/application-performance-class/ |url-status=live }}</ref>
|-
! rowspan="2" | Rating
! colspan="2" | Minimum random [[IOPS]]
! rowspan="2" | Minimum sustained<br>sequential writing
|- 
! Read
! Write
|- 
| style="background:white" | {{Nowrap|Class 1 (A1)}}<br />[[File:SD App Performance 1.svg|x20px]]
| 1,500
| 500
| rowspan="2" |{{Nowrap|10 MB/s}}
|-
| style="background:white" | {{Nowrap|Class 2 (A2)}}<br />[[File:SD App Performance 2.svg|x20px]]
| 4,000
| 2,000
|}

'''Application Performance Class''' ratings were developed to address the increasing demand for SD memory cards capable of supporting both application storage and execution in mobile and embedded systems, while also supporting general-purpose data storage such as photos, videos, music, and documents. This need became more prominent with the growing use of SD cards for storing apps and application data, particularly following the introduction of Android's [[Adoptable Storage]] feature, which allows SD cards to function as internal (non-removable) storage.<ref>{{Cite web |title=Adoptable storage |url=https://source.android.com/docs/core/storage/adoptable |access-date=2025-04-12 |website=Android Open Source Project |language=en |archive-date=12 April 2025 |archive-url=https://web.archive.org/web/20250412032605/https://source.android.com/docs/core/storage/adoptable |url-status=live }}</ref>

Class A1, as defined in the SD Specification 5.1, requires a minimum of 1,500 input/output operations per second (IOPS) for reading and 500 IOPS for writing, using 4&nbsp;kB data blocks. Class A2, introduced in the SD Specification 6.0, raises these thresholds to 4,000 read and 2,000 write IOPS. A2 cards also depend on host driver support for features such as command queuing and write caching to achieve their specified performance; without this support, they operate at or above A1-level performance. Both A1 and A2 classes additionally require a minimum sustained sequential write speed of 10&nbsp;MB/s.<ref>"{{cite web |date=November 2016 |title=Application Performance Class: The new class of performance for applications on SD memory cards (SD 5.1) |url=https://www.sdcard.org/downloads/pls/latest_whitepapers/Application_Peformance_Class_White_Paper.pdf |url-status=live |archive-url=https://web.archive.org/web/20161123202004/https://www.sdcard.org/downloads/pls/latest_whitepapers/Application_Peformance_Class_White_Paper.pdf |archive-date=2016-11-23 |access-date=2024-09-11 |website=sdcard.org}}</ref>