RAID 5 and 10 on Adaptec 3805 – performance comparison
Last weekend I’ve been evaluating my work on qKAI and thus worked extensively with datasets of about 30 GB in MySQL, with DBPedia dumps. To speed up file read I’ve added my spare fourth Western Digital WD6400AAKS to Adaptec 3805 RAID and:
- done online RAID level migration from RAID 5 with three HDD to RAID 10 to four HDD,
in the hope writing performance will increas as suggested by this article - ran ATTO disk benchmark on the new array
- been unsatisfied, and (again) converted the RAID 10 to a four-drive RAID 5
- now been puzzled about Windows Server showing free areas strangely
and not letting me expand the primary partition the volume’s new size
Conversions took longer than I expected. From 3 HDD RAID 5 to 4 HDD RAID 10 about 72 hours, conversion priority was set to ‘medium’, though. And from 4 HDD RAID 10 to 4 HDD RAID 5 surprising 36 hours at priority ‘high’ – during latter I watched some videos, so take these numbers as rough approximation.
What upset me the most is, that the first conversion should take about ten to twelve hours. After that I’ve urgently wanted to work with database again. It took so long it turned out being counterproductive at that time. Were it not my clement supervisoress, I ran into serious trouble being behind schedule.
Performance of RAID 10 was high, but not that high I expected. RAID 10 is said to be faster in writes and, on Adaptec 3805, no slower in reading than equally equipped RAID 5. I’ve measured no difference. Indeed, even with 4 HDD RAID 5 I cannot measure anything beyond tolerance. (Conversion completed just an hour ago, so I can start deploying qKAI by tomorrow.)
Here are my ATTO disk benchmark results. There must be something I’ve done wrong. (Transfer length affects only measure duration.)
After having expanded RAID 5 by a fourth HDD I want to do this with Windows’ primary partition as well. Server 2008 supports online partition expansion (and shrinking, btw), but currently lets me only select the first free part – of two free parts. What the..? Why even is there a distinction, why does Windows not pool ‘em? A reboot helped, but by doing online expansion this was something what I wanted to avoid.
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