On 2014-09-08, Valeri Galtsev galtsev@kicp.uchicago.edu wrote:
Then you too manage to stick with reliable drives! Performance... well, I have array verify scheduled to start 23:00 on Saturday... also, on newer controllers you can choose policy with highest priority for IO and lowest for rebuild etc. I'm kind of sceptical about extra wear to mechanical drives added by RAID check: my drives are always spinning full speed (no spin down crap, thank you), and heads are not touching the platters... So, I'm not certain there is extra wear. The only wear apart from bearings I know about is when arm hits the stopper which only happens when you power off the drive, which not the case here too. What do I miss?
I learned the "reliable drive" lesson the hard way, when I accidentally ordered, and then unwisely decided to use, crappy drives. Fortunately no data was ever lost, but the drives made a lot of extra work for me.
You may be 100% correct about wear. I have no actual evidence that extra verifies causes more wear than normal use.
For my largest arrays, even if I started at 23:00 on Saturday, it would still be going through much of Sunday. Plus I have other disk operations that occur overnight. The performance loss isn't terrible during a verify, but I have noticed it enough that I prefer to avoid it happening so frequently.
I've heard quite a few horror stories from people who never did a scrub of their arrays. But I haven't heard any from people who did scrubs less frequently than weekly. Has anyone? I'm genuinely curious; if there's a justification for weekly scrubs that's stronger than my fairly weak justifications for monthly, I'd switch back.
--keith