Hi
I appeal to any geeks, and in particular tecnicians at VSL to help me, please.
I am using RAID arrays to both speed up and secure my Vienna Library. All this on a Mac. (Please no platform flaming here). I'm not planning to go SSD as yet - although my question would still apply in that case too.
Now, for some time I have been formatting and managing my RAIDS using the highly respected SoftRAID 4.0 utility and drivers. The great thing about SR is that it has the capability to READ from a mirror, across all members of the RAID at once. Unlike the Apple software RAID, that will only read from the primary disk of a Mirror RAID. The advantage of this should be clear: you get Stripe equivalent read speeds, but Mirror security. In some situations the read will outperform a stripe. SR has many other advantages I won't go into here (email notification of drive failures is one example).
However, in some real world tests, I have found that a SR formatted mirror RAID with 3 members is taking longer to load up a large project than a sinlge no raided disk. WTF I'm thinking.
After speaking with SoftRaid technical support, it appears that under normal circumstances, the SR driver is multithreaded, and transparent to the OS. So a multithreaded application should in theory benefit from the multi-disk mirror read strategy of SR. But, there are situatiions were the SR driver will only use 1 thread (and heance 1 disk) and a notable example of this is disk speed test utilities, as they operate on a deeper level thatn the OS in order to control their test conditions (thereby bypassing SR in effect). No multithreaded disk speed test applications seem to exist at this time for OSX.
My questions is, does VEPro use OS level disk reading, multithreaded, or does it use deeper methods to read, possibly inadvertently bypassing all the advantages of a multidisk mirror read? Does VEPro load "everything at once" or does it plod through instrument by instrument?
And, does VEPRo do writing to disk as part of the load process? If so, this would possibly explain the anomaly - as obviously a mirror can only ever write to disk at the same speed as the slowest drive in the array.
I would especially welcome some input on this form VSL technicians, although any real world experiences really count for the most useful knowledge. And does any one else out there use SoftRAID 4?
Many thanks
Ben
