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Bootable Linux USB stick: Difference between revisions
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== Hardware considerations == | == Hardware considerations == | ||
Cheap USB sticks can hold a lot of data, but when it comes to writing small files (which happens when used as the operating system disk), they are either slow from the beginning, or their write performance quickly degrades as soon as free space becomes low for the first time. We have been using [https://crystalmark.info/software/CrystalDiskMark/index-e.html CrystalDiskMark] (Windows) for characterizing USB media: as a rule of thumb, the "Random write 4k blocks" disciplines should | Cheap USB sticks can hold a lot of data, but when it comes to writing small files (which happens when used as the operating system disk), they are either slow from the beginning, or their write performance quickly degrades as soon as free space becomes low for the first time. We have been using [https://crystalmark.info/software/CrystalDiskMark/index-e.html CrystalDiskMark] (Windows) for characterizing USB media: as a rule of thumb, the "Random write 4k blocks" disciplines should at least 1 MB/s, and for sequential writes the numbers should >50 MB/s. However, CrystalDiskMark does not capture the effect of degrading write performance, which can only be mitigated by TRIMming the media - a feature that few USB sticks support (see below). | ||
The following is about performance and durability of the USB media. If you don't know what TRIM is and how it relates to flash media, read [https://en.wikipedia.org/wiki/Trim_(computing) this]. | The following is about performance and durability of the USB media. If you don't know what TRIM is and how it relates to flash media, read [https://en.wikipedia.org/wiki/Trim_(computing) this]. | ||
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=== types of USB media === | === types of USB media === | ||
The suitability of the media makes a notable difference, in particular when the operating system | The suitability of the media makes a notable difference, in particular when the operating system or CCP4 is upgraded, or when e.g. a new Phenix version is installed. | ||
* very good: USB sticks that support TRIM. The ones known to us are the Sandisk Extreme USB sticks bought before 2017 (e.g. the SDCZ80-032G 32GB model for ~22€ or 64GB for ~40€; unfortunately, these are no longer available or very costly). These sticks are very fast (CrystalDiskMark scores >10MB/s for random 4K writes). The successor are the differently-named current (2018) Sandisk Extreme Pro USB sticks, but only 128 and 256 GB models exist, and they are expensive. | * very good: USB sticks that support TRIM. The ones known to us are the Sandisk Extreme USB sticks bought before 2017 (e.g. the SDCZ80-032G 32GB model for ~22€ or 64GB for ~40€; unfortunately, these are no longer available or very costly). These sticks are very fast (CrystalDiskMark scores >10MB/s for random 4K writes). The successor are the differently-named current (2018) Sandisk Extreme Pro USB sticks, but only 128 and 256 GB models exist, and they are expensive. | ||
* good: we have verified that a USB3 adapter with (micro)SD card (separate items) is suitable. USB3 adapters are cheap (around 5€ at Amazon, like https://www.amazon.de/EX1-Kartenleser-Micro-Karte-Adapter/dp/B06XX3T219; cheaper at Ebay). microSD cards usually come with a SD adapter, and can be TRIMmed (but only in a SD slot; see below!). microSD cards ideally should be in the [https://en.wikipedia.org/wiki/Secure_Digital#Speed_class_rating Class 1 (A1) application performance class] since this is what is defined as requirement for use as extended operating system disk in Android smartphones. In practice, cheaper non-A1 microSD cards also seem to work well, but may be slower and may require more often TRIMming. The price/performance ratio of the microSD/USB3 combination is very good. | * good: we have verified that a USB3 adapter with (micro)SD card (separate items) is suitable. USB3 adapters are cheap (around 5€ at Amazon, like https://www.amazon.de/EX1-Kartenleser-Micro-Karte-Adapter/dp/B06XX3T219; cheaper at Ebay). microSD cards usually come with a SD adapter, and can be TRIMmed (but only in a SD slot; see below!). microSD cards ideally should be in the [https://en.wikipedia.org/wiki/Secure_Digital#Speed_class_rating Class 1 (A1) application performance class] since this is what is defined as requirement for use as extended operating system disk in Android smartphones. 64GB A1 microSD cards cost around 25€. In practice, slightly cheaper non-A1 microSD cards also seem to work well, but may be slower and may require more often TRIMming. The price/performance ratio of the microSD/USB3 combination is very good. | ||
* acceptable: USB sticks that do not support TRIM but are fast and high quality, e.g. Sandisk Extreme Go or Sandisk Ultra bought 2017 and later. However, their write performance may degrade with time (or rather, with the number of writes to a partition), and not much can be done about that. | * acceptable: USB sticks that do not support TRIM but are fast and high quality, e.g. Sandisk Extreme Go or Sandisk Ultra bought 2017 and later. However, their write performance may degrade with time (or rather, with the number of writes to a partition), and not much can be done about that. | ||
* inacceptable: tiny sticks like Sandisk Ultra Fit become hot, degrade fast and are unreliable. Cheap sticks are too slow. | * inacceptable: tiny sticks like Sandisk Ultra Fit become hot, degrade fast and are unreliable. Cheap sticks are usually just too slow. | ||
The drawback of the "good" solution above is: from time to time (e.g. once every week), a knowledgeable person should | The drawback of the "good" solution above is: from time to time (e.g. once every week), a knowledgeable person should | ||