Barriers and journaling filesystems [LWN.net]

Barriers and journaling filesystems

Posted May 21, 2008 20:15 UTC (Wed) by evgeny (subscriber, #774)
In reply to: Barriers and journaling filesystems by raven667
Parent article: Barriers and journaling filesystems

> it would be I think most effective if drives had their own battery backed write-back cache

This would be as controversial as using battery modules for some RAID controllers. Many folks
don't like this idea - if we talk reliability, a UPS is a must. Then an extra battery could
only be a source of extra trouble.

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Barriers and journaling filesystems

Posted May 21, 2008 22:28 UTC (Wed) by iabervon (subscriber, #722) [Link]

Having a UPS is great until the cat turns it off or the battery ages to the point where power
fluctuations cause it to reset or somebody turns off the computer's power switch or the power
supply burns out. Even if the outside power situation is well-protected, there's value to
having the drive store enough power to finish with its buffers and spin down carefully and
such.

Barriers and journaling filesystems

Posted May 22, 2008 18:42 UTC (Thu) by amikins (subscriber, #451) [Link]

> Having a UPS is great until the cat turns it off

I'm NOT the only one that's been plagued by this? I've since learned to make cat-proof covers
for my UPS buttons...

Barriers and journaling filesystems

Posted May 22, 2008 20:03 UTC (Thu) by v13 (subscriber, #42355) [Link]

Why would anyone not like the battery backed cache?

Have you ever considered the effects of not having to do a disk write 
when doing synchronous disk operations? Journals and databases perform a 
*lot* faster on BB controllers. (based on my experience).

Consider no having to do any safety-related writes to disk for safety. 
Even barriers have zero overhead.