Yeah. It is also not so easy to capture the possible data loss during. There is no reliable way to figure it out.
Thanks. Fred. -----Original Message----- From: rwali...@washdcmail.com [mailto:rwali...@washdcmail.com] Sent: 星期二, 五月 25, 2010 11:42 To: Erik Trimble Cc: Fred Liu; ZFS Discussions Subject: Re: [zfs-discuss] [ZIL device brainstorm] intel x25-M G2 has ram cache? On May 24, 2010, at 4:28 AM, Erik Trimble wrote: > yes, both the X25-M (both G1 and G2) plus the X25-E have a DRAM buffer on the > controller, and neither has a supercapacitor (or other battery) to back it > up, so there is the potential for data loss (but /not/ data corruption) in a > power-loss scenario. > > Sadly, we're pretty much at the point where no current retail-available SSD > has battery backup for it's on-controller DRAM cache (and, they /all/ use > DRAM caches). I haven't seen where anyone has tested this, but the MemoRight SSD (sold by RocketDisk in the US) seems to claim all the right things: http://www.rocketdisk.com/vProduct.aspx?ID=1 pdf specs: http://www.rocketdisk.com/Local/Files/Product-PdfDataSheet-1_MemoRight%20SSD%20GT%20Specification.pdf They claim to support the cache flush command, and with respect to DRAM cache backup they say (p. 14/section 3.9 in that pdf): > The MemoRight’s NSSD have an on-drive backup power system. It saves energy > when the power supply is applied to drive. When power-off occurring, the > saved energy will be released to keep the drive working for a while. The > saved energy ensures the data in the cache can be flushed to the nonvolatile > flash media, which prevents the data loss to happen. > It will take about 5 seconds to save enough energy for discharge at lease 1 > second. The write cache will be disabled automatically before the backup > power system saved enough energy. Which certainly sounds like an on-board capacitor to flush the cache and that the cache is disabled while charging the capacitor. But I can't see where anyone has tested this on ZFS. --Ware _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
