From: | mudfoot(at)rawbw(dot)com |
---|---|
To: | pgsql-performance(at)postgresql(dot)org |
Subject: | Re: Battery Backed Cache for RAID |
Date: | 2005-09-14 21:58:28 |
Message-ID: | 1126735108.43289d040898d@webmail.rawbw.com |
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Thread: | |
Lists: | pgsql-performance |
Bear in mind you will lose data if the raid controller itself fails (or the
cache memory module). Many solutions have mirrored cache for this reason. But
that's more $$, depending on the risks you want to take.
Quoting Arjen van der Meijden <acmmailing(at)tweakers(dot)net>:
> On 14-9-2005 22:03, Alvaro Herrera wrote:
> > On Wed, Sep 14, 2005 at 11:28:43AM -0700, Jeffrey W. Baker wrote:
> >
> >>On Wed, 2005-09-14 at 11:25 -0700, Peter Darley wrote:
> >>
> >>Actually the cache will just hold its contents while the power is out.
> >>When the power is restored, the RAID controller will complete the writes
> >>to disk. If the battery does not last through the outage, the data is
> >>lost.
> >
> >
> > Just curious: how long are the batteries supposed to last?
>
> For the LSI-Logic MegaRaid 320-2e its about 72 hours for the standard
> 128MB version. Their SATA2-solution offers 32 and 72 hour-options. So I
> assume its "in the order of days" for most RAID controllers.
>
> Best regards,
>
> Arjen van der Meijden
>
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