Another weekend without much ado. Our assimilator queue is low but not exactly pegged at zero. What's causing it to not run as fast as all the other backend processes? Not entirely sure, but we know of several things that happen from time to time which may be the problem (i.e. cause extra load on the science database), or at least aggravate the problem. But for now, it's not even close to a tragedy, so we're just keeping our eye on it.

I guess we did have a disk failure on thumper (the master science database server), or at least disk complaint. It didn't cause any downtime or data loss, but it's getting us to reconsider our current stance on software vs. hardware RAID. We've been sticking with software RAID due to ease of use and quickness of warning, but we're finding it sometimes doesn't behave the exact way we expect, or sometimes not the best way. So this event inspired some additional R&D on that front

I just rebooted the main web server, so that was offline for a couple minutes. No big deal - just some mounting issues that needed to be cleared out.

- Matt

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-- BOINC/SETI@home network/web/science/development person
-- "Any idiot can have a good idea. What is hard is to do it." - Jeanne-Claude

. . . Thanks for the Update Matt - Nice going Berkeley

@ Eric - Enjoy that Visit Sir!

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BOINC Wiki . . .

Science Status Page . . .

If thumper is one of your Linux box's, then I assume your using mdadm. Maybe posting to the linux-raid mailing list (if you haven't already done so) with whatever problems your having, They seem a pretty friendly bunch and you may even get help from the man himself (Neil Brown)

http://vger.kernel.org/vger-lists.html#linux-raid

Personally I'd stick to software RAID and work on fixing any issues you have. Been bitten by hardware RAID before, RAID controller died, hosting company didn't have any more of that kind that would read the ondisk format, had to restore from backup.

Got a couple of small software (mdadm) RAID 5 arrays in the office (466GB and 2.1TB).


Cheers and keep up the good work.

Andrew

While software raid is cheaper and easier to implement they are not safe and efficient as hardware based raids. Although somehow expensive they perform better, all the overhead to maintain checksums and recovery is done by the onboard processor, recovery from hardware failures are a lot less painful and some even allow to do some volume housekeeping on the fly (expansion, raid type migration, etc). In my experience the extra cost pays for itself on the first failure recovery.

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One other advantage of software RAID is that you aren't locked in to a particular vendor and can easily move your RAID array from one machine to another.

As for performance I'm not sure it's specifically true that hardware RAID outperfoms software RAID these days with the CPU power available. True, there may be areas where Linux's RAID implementation could be improved.

There is also the work from Intel to allow a lot of the work to be offloaded to Intel Xscale IOP I/O processors, see:
http://marc.info/?l=linux-raid&m=118434090621144&w=2

Andrew