> -----Original Message----- > From: Erik Trimble [mailto:erik.trim...@oracle.com] > Sent: 星期四, 七月 01, 2010 11:45 > To: Fred Liu > Cc: Bob Friesenhahn; 'OpenSolaris ZFS discuss' > Subject: Re: [zfs-discuss] OCZ Vertex 2 Pro performance numbers > > On 6/30/2010 7:17 PM, Fred Liu wrote: > > See. Thanks. > > Does it have the hardware functionality to detect the power outage > and do force cache flush when the cache is enabled? > > Any more detailed info about the capacity (farad) of this supercap > and how long one discharge will be? > > > > Thanks. > > > > Fred > > > > > > I don't think it matters the actual size of the supercap. As Bob said, > it only needs to be sized to be big enough to allow all on-board DRAM > to > be flushed out to Flash. How big that should be is easily determined by > the manufacturer, and they'd be grossly negligent if it wasn't at least > that size. Any capacity beyond that needed to do a single full flush is > excess, so I would hazard a guess that the supercap is "just big enough, > and no more". That is, just enough to power the SSD for the partial > second or so it takes to flush to flash. I don't think we need to worry > how big that actually is.
Understand and agree. It is sort of picky to ask this without manufacturer's help ;-) > > Answering your second question first - my reading of the info is that > it > will force a cache flush (if the cache is enabled) upon loss of power > under any circumstance. That is, it will flush the cache in both a > controlled power-down (regardless of whether the OS says to do so) and > in an immediate power loss. All this is in the SSD's firmware. That is exactly what I expect. Little bit broadly speaking, it is sort of ambiguous in aspect of cache flush in all the HDDs. Is it OS-controlled or firmware-controlled or both? At least in this case, I have got what I expect. But what about for all(generic) the HDDs? Thanks. Fred > > -Erik > > > > -----Original Message----- > > From: Bob Friesenhahn [mailto:bfrie...@simple.dallas.tx.us] > > Sent: 星期四, 七月 01, 2010 10:01 > > To: Fred Liu > > Cc: 'OpenSolaris ZFS discuss' > > Subject: Re: [zfs-discuss] OCZ Vertex 2 Pro performance numbers > > > > On Wed, 30 Jun 2010, Fred Liu wrote: > > > > > >> Any duration limit on the supercap? How long can it sustain the data? > >> > > A supercap on a SSD drive only needs to sustain the data until it has > > been saved (perhaps 10 milliseconds). It is different than a RAID > > array battery. > > > > Bob > > > > > -- > Erik Trimble > Java System Support > Mailstop: usca22-123 > Phone: x17195 > Santa Clara, CA > Timezone: US/Pacific (GMT-0800) > _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
