It was quite surprising to me that that Chattel slavery existed in the Ottoman Empire. Here's the relevant section:
Quantitatively, the most important traffic in slave chattel and captive occurred with the Ottoman Empire. The Russian Empire interacted with Islamic regions where chattel slavery was common and regarded as the only legitimate form of coerced labour under Islamic law.
Muslim Tatars of the Crimea raided widely for Russian subjects as well as other eastern Slavs, Poles and Lithuanians, and they exported most of their captives to the Ottomans.
In 1529, half of all the slaves in the Ottoman Crimea were identified as coming from Ukraine and Muscovy; the other half were Circassians. From the 1 570s, about 20,000 slaves were sold annually in the port of Caffa on the Black Sea.•s Until the early seventeenth century,
Russians and above all Cossacks also sold captives to the Tarars or directly to the Ottomans.The Ottoman rules on slave trading distinguished between slaves who were brought from the Tatar and Circassian areas and chose from Onoman territories such as Azov and Taman. The tax on the latter was half of that on the former group.
Is any of this true?
It is true. Slavery in the Ottoman Empire is not as famous as slavery in the West but it certainly survived well into the 19th century and even in some forms into the 20th century, like the royal concubines. The main sources of slaves were the ones described above. Circassian slaves were particularly popular in the empire. There were also slaves from Africa, mainly from Sudan. Raids of the Tatars into Russian lands were also notorious, so that too is correct.
Slavery in the Ottoman Empire and among Muslims at large is less well-known than slavery in Europe and the Americas. Why? I do not know, maybe it has something to do with the politicisation, or maybe the Ottomans had fewer slaves than the West compared quantitatively, so it was less noticed, or maybe because the racial tension in the region is much less accentuated than it is in the US. Whatever it is, clearly nobody is quite as shocked to learn that there once existed slaves in Europe, but this happens at times with the Ottoman Empire.
You might check out the work of Ceyda Karamursel for learning more about slavery in the Ottoman Empire, especially about its manifestations in the 19th and 20th centuries.
Absolutely did piracy and slavery exist within the Ottoman Empire. Most notably were the Barbary coast, where many pirates sailed out to loot, enslave and ransack Christian settlements throughout the world. One notable example of this is the attack on Iceland 1627, where they enslaved most of population of a village and brought them to Algiers. As a part of my Masters degree, I wrote a paper on the book; ‘The Travels of Reverend Olafur Egilsson’ wherein the priest in question was captured in 1627 and brought to Algiers, where he was able to note down encounters with other slaves he met in Algiers, some of whom were from Eastern Europe. Not before the French captured Algiers and Tunis in 1830 did the piracy from the region slow down and the danish state continued up to this period to pay ransom for those captured by the “Turks”. Egilsson and his family were one of those that were bought back from slavery by the Danish crown.
I strongly suggest giving the mentioned book a read if interested more. Sorry for the short reply, hope it gave some insight!