David Wein

In ASE 12.0 we introduced official file system device support via the device-level dsync flag. Since then, many a DBA has pondered "to dsync, or not to dsync?" This tends to be part of the larger question of file versus raw. Like just about anything related to performance, there is not really a yes or no answer that fits all cases. In this article I'll try to further your understanding of this and other device options. I like to have an understanding of what a flag/switch/etc., really does before making a decision on its use, so I'll start my discussion of device flags with an explanation as to what they really are. Before we talk about the various flags, let's take a look at file system i/o in general (generalizations and simplifications will be fine for this portion). A typical file system has a cache into which blocks are read and written. You can think of this v... (more)