data loss after power failure

[Micha Silver]

shimi wrote:

>
>
> On Thu, Aug 13, 2009 at 9:59 AM, Micha Silver <micha at arava.co.il 
> <mailto:micha at arava.co.il>> wrote:
>
>     We suffered some annoying file and directory corruption on a
>     CentOS 5.3 64 bit server two days ago after a long power failure -
>     long enough to drain the UPS battery, with several short "spurts"
>     of power until it finally stabilized. Files appeared as
>     directories, directories turned into files, duplicated inodes, in
>     short, a mess. And most of the corruption was under /usr, i.e.
>     *not* files that were being written to when the power went off.
>     The file system is ext3 but the journaling didn't help - well
>     maybe it did, but not enough...
>
>
>     The machine is a Dell PE 840 with their PERC 5i controller and 4
>     SATA disks in a RAID 5 array. It has its own battery backup to
>     preserve the writeback cache in case of power failure (but again
>     the files that got "kevorked" were not being written...). And it's
>     relatively new ( < 2 yrs). Two identical machine attached to the
>     same UPS, but w/o RAID came thru the event with no problems. And
>     other, older servers with SCSI disks also showed no ill effects.
>
>     Does anyone have any ideas how to prevent this kind of thing in
>     the future? (short of adding lots of additional batteries)
>
>
> Sample the UPS unit for "how much battery time left do you have?"  and 
> initiate automatic shutdown when the number falls below the 5 minutes 
> threshold ?
>
Yes, that's probably best. Thanks. The disadvantage is that after the 
power comes back, someone has to physically go to power-up the servers.
> -- Shimi
>
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