Black Candles are bearish lines in candlestick and candlevolume charts. They signify that the closing is lower than opening for that time period.
CHKDSK, short for Check Disk, is a utility that checks the integrity of the files and file structure of your hard disk. I'll walk you through it. I have disk problems and you said I should run CHKDSK. Great.
Simplest Test: The DD Test. This test measures the most basic single-threaded disk access: a large sequential write, followed by a large sequential read. It is relevant to database performance because it gives you a maximum speed for sequential scans for large tables. Real table scans are generally about 30% of this maximum. dd is a Unix command line utility which simply writes to a block device. We use it for this 3-step test.