Re: [zfs-discuss] [ZIL device brainstorm] intel x25-M G2 has ram cache?
--On 24 May 2010 23:41 -0400 rwali...@washdcmail.com wrote: 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%20 SSD%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): At the risk of this getting a little off-topic (but hey, we're all looking for ZFS ZIL's ;) We've had similar issues when looking at SSD's recently (lack of cache protection during power failure) - the above SSD's look interesting [finally someone's noted you need to protect the cache] - but from what I've read about the Intel X25-E performance - the Intel drive with write cache turned off appears to be as fast, if not faster than those drives anyway... I've tried contacting Intel to find out if it's true their enterprise SSD has no cache protection on it, and what the effect of turning the write cache off would have on both performance and write endurance, but not heard anything back yet. Picking apart the Intel benchmarks published - they always have the write-cache enabled, which probably speaks volumes... -Karl ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
Re: [zfs-discuss] [ZIL device brainstorm] intel x25-M G2 has ram cache?
On Tue, May 25, 2010 at 10:08:57AM +0100, Karl Pielorz wrote: --On 24 May 2010 23:41 -0400 rwali...@washdcmail.com wrote: 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%20 SSD%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): At the risk of this getting a little off-topic (but hey, we're all looking for ZFS ZIL's ;) We've had similar issues when looking at SSD's recently (lack of cache protection during power failure) - the above SSD's look interesting [finally someone's noted you need to protect the cache] - but from what I've read about the Intel X25-E performance - the Intel drive with write cache turned off appears to be as fast, if not faster than those drives anyway... I've tried contacting Intel to find out if it's true their enterprise SSD has no cache protection on it, and what the effect of turning the write cache off would have on both performance and write endurance, but not heard anything back yet. I guess the problem is not the cache by itself, but the fact that they ignore the CACHE FLUSH command.. and thus the non-battery-backed cache becomes a problem. -- Pasi Picking apart the Intel benchmarks published - they always have the write-cache enabled, which probably speaks volumes... -Karl ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
Re: [zfs-discuss] [ZIL device brainstorm] intel x25-M G2 has ram cache?
--On 25 May 2010 15:28 +0300 Pasi Kärkkäinen pa...@iki.fi wrote: I've tried contacting Intel to find out if it's true their enterprise SSD has no cache protection on it, and what the effect of turning the write cache off would have on both performance and write endurance, but not heard anything back yet. I guess the problem is not the cache by itself, but the fact that they ignore the CACHE FLUSH command.. and thus the non-battery-backed cache becomes a problem. The X25-E's do apparently honour the 'Disable Write Cache' command - without write cache, there is no cache to flush - all data is written to flash immediately - presumably before it's ACK'd to the host. I've seen a number of other sites do some testing with this - and found that it 'works' (i.e. with write-cache enabled, you get nasty data loss if the power is lost - with it disabled, it closes that window). But you obviously take quite a sizeable performance hit. We've got an X25-E here which we intend to test for ourselves (wisely ;) - to make sure that is the case... -Karl ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
Re: [zfs-discuss] [ZIL device brainstorm] intel x25-M G2 has ram cache?
On Tue, May 25, 2010 at 01:52:47PM +0100, Karl Pielorz wrote: --On 25 May 2010 15:28 +0300 Pasi Kärkkäinen pa...@iki.fi wrote: I've tried contacting Intel to find out if it's true their enterprise SSD has no cache protection on it, and what the effect of turning the write cache off would have on both performance and write endurance, but not heard anything back yet. I guess the problem is not the cache by itself, but the fact that they ignore the CACHE FLUSH command.. and thus the non-battery-backed cache becomes a problem. The X25-E's do apparently honour the 'Disable Write Cache' command - without write cache, there is no cache to flush - all data is written to flash immediately - presumably before it's ACK'd to the host. I've seen a number of other sites do some testing with this - and found that it 'works' (i.e. with write-cache enabled, you get nasty data loss if the power is lost - with it disabled, it closes that window). But you obviously take quite a sizeable performance hit. Yeah.. what I meant is: if you have write cache enabled, and the ssd drive honours 'CACHE FLUSH' command, then you should be safe.. Based on what I've understood the Intel SSDs ignore the CACHE FLUSH command, and thus it's not safe to run them with caches enabled.. We've got an X25-E here which we intend to test for ourselves (wisely ;) - to make sure that is the case... Please let us know how it goes :) -- Pasi ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
Re: [zfs-discuss] [ZIL device brainstorm] intel x25-M G2 has ram cache?
On Tue, May 25, 2010 at 2:08 AM, Karl Pielorz kpielorz_...@tdx.co.uk wrote: I've tried contacting Intel to find out if it's true their enterprise SSD has no cache protection on it, and what the effect of turning the write The E in X25-E does not mean enterprise. It means extreme. Like the EE series CPUs that Intel offers. -B -- Brandon High : bh...@freaks.com ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
Re: [zfs-discuss] [ZIL device brainstorm] intel x25-M G2 has ram cache?
--On 25 May 2010 11:15 -0700 Brandon High bh...@freaks.com wrote: On Tue, May 25, 2010 at 2:08 AM, Karl Pielorz kpielorz_...@tdx.co.uk wrote: I've tried contacting Intel to find out if it's true their enterprise SSD has no cache protection on it, and what the effect of turning the write The E in X25-E does not mean enterprise. It means extreme. Like the EE series CPUs that Intel offers. Yet most of their web site seems to aim it quite firmly at the 'Enterprise' market, Imagine replacing up to 50 high-RPM hard disk drives with one Intel® X25-E Extreme SATA Solid-State Drive in your servers or, Enterprise applications place a premium on performance, reliability, power consumption and space. If you don't mind a little data loss risk? :) I'll post back when we've had a chance to try one in the 'real world' for our applications - with and without caching, especially when the plug gets pulled :) Otherwise, at least on the surface the quest for the 'perfect' (performance, safety, price, size) ZIL continues... -Karl ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
Re: [zfs-discuss] [ZIL device brainstorm] intel x25-M G2 has ram cache?
On 5/23/2010 11:30 PM, Fred Liu wrote: Hi, I have hit the synchronous NFS writing wall just like many people do. There also have lots of discussion about the solutions here. I want to post all of my exploring fighting done recently to discuss and share: 1): using the normal SATA-SSDs(intel/ocz) as ZIL device. For intel just EOLed 50nm SSDs product line and the spec of the x25-M G2(34nm) 160G is getting more decent, I used this one. I get good performance boost compared with no slog. I also manually did unplugging power server times, the outcome seems good -- I got no data corruption. But there is always potential risk -- does it have built-in ram cache? We get no clear answer from intel. 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). 2): using PCIE-SSD(i.e. fusionio's ioDrive). For the universal standard of PCIE-SSD is still on the way, the responding driver under solaris become apparent. And also the cost is very high. Yes, you do have to find those with Solaris drivers. Fortunately, pretty much all the manufacturers recognize the big market that ZFS/Solaris has for these devices, so most already have Solaris drivers, and the rest are almost universally working to produce them. 3): using PCIE-DRAM-with(out)-SSD(i.e. marvell's write acceleration module (WAM), ddrdrive X1, curtisssd's HyperCache. It has the higest spec but the same driver and high cost issue. Yup. 4): using SATA--DRAM-with(out)-SSD(i.e acard's 9010, curtisssd's HyperHD). No driver issue and price is in the middle. I also tried acard 9010, the result is good enough. Frankly, these are about the best available solution, without breaking the bank. The bad news is that they're not quite read-for-prime-time yet in terms of support and packaging. So it seems we have to wait awhile to get a really ideal ZIL device solution. If intel/ocz can confirm no ram cache, that will be good news. Thanks. Fred Nope, ALL SSDs use DRAM caches for their controllers. So far, I'm only aware that the Zeus stuff (plus a couple of industrial/military-only products) have battery backup for their controllers. Idiots - it's like $0.50 in parts, and a one-time $10,000 in engineer design/qa time to put the damned thing on, and they could charge a 25% premium and we'd pay it. Frankly, I'm really surprised that there's no solution, given that the *amount* of NVRAM needed for ZIL (or similar usage) is really quite small. a dozen GB is more than sufficient, and really, most systems do fine with just a couple of GB (3-4 or so). Producing a small, DRAM-based device in a 3.5 HD form-factor with built-in battery shouldn't be hard, and I'm kinda flabberghasted nobody is doing it. Well, at least in the sub-$1000 category. I mean, it's 2 SODIMMs, a AAA-NiCad battery, a PCI-E-DDR2 memory controller, a PCI-E to SATA6Gbps controller, and that's it. -- Erik Trimble Java System Support Mailstop: usca22-123 Phone: x17195 Santa Clara, CA ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
Re: [zfs-discuss] [ZIL device brainstorm] intel x25-M G2 has ram cache?
From: Erik Trimble [mailto:erik.trim...@oracle.com] Sent: 星期一, 五月 24, 2010 16:28 To: Fred Liu Cc: ZFS Discussions Subject: Re: [zfs-discuss] [ZIL device brainstorm] intel x25-M G2 has ram cache? On 5/23/2010 11:30 PM, Fred Liu wrote: Hi, I have hit the synchronous NFS writing wall just like many people do. There also have lots of discussion about the solutions here. I want to post all of my exploring fighting done recently to discuss and share: 1): using the normal SATA-SSDs(intel/ocz) as ZIL device. For intel just EOLed 50nm SSDs product line and the spec of the x25-M G2(34nm) 160G is getting more decent, I used this one. I get good performance boost compared with no slog. I also manually did unplugging power server times, the outcome seems good -- I got no data corruption. But there is always potential risk �C does it have built-in ram cache? We get no clear answer from intel. 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). [Fred]: Yes. It is correct. I totally agree. 2): using PCIE-SSD(i.e. fusionio’s ioDrive). For the universal standard of PCIE-SSD is still on the way, the responding driver under solaris become apparent. And also the cost is very high. Yes, you do have to find those with Solaris drivers. Fortunately, pretty much all the manufacturers recognize the big market that ZFS/Solaris has for these devices, so most already have Solaris drivers, and the rest are almost universally working to produce them. [Fred]: Yes. Hope we can see the very first standard soon just like USB… 3): using PCIE-DRAM-with(out)-SSD(i.e. marvell’s write acceleration module (WAM), ddrdrive X1, curtisssd’s HyperCache. It has the higest spec but the same driver and high cost issue. Yup. 4): using SATA--DRAM-with(out)-SSD(i.e acard’s 9010, curtisssd’s HyperHD). No driver issue and price is in the middle. I also tried acard 9010, the result is good enough. Frankly, these are about the best available solution, without breaking the bank. The bad news is that they're not quite read-for-prime-time yet in terms of support and packaging. [Fred]: Agree. So it seems we have to wait awhile to get a really ideal ZIL device solution. If intel/ocz can confirm no ram cache, that will be good news. Thanks. Fred Nope, ALL SSDs use DRAM caches for their controllers. So far, I'm only aware that the Zeus stuff (plus a couple of industrial/military-only products) have battery backup for their controllers. Idiots - it's like $0.50 in parts, and a one-time $10,000 in engineer design/qa time to put the damned thing on, and they could charge a 25% premium and we'd pay it. Frankly, I'm really surprised that there's no solution, given that the *amount* of NVRAM needed for ZIL (or similar usage) is really quite small. a dozen GB is more than sufficient, and really, most systems do fine with just a couple of GB (3-4 or so). Producing a small, DRAM-based device in a 3.5 HD form-factor with built-in battery shouldn't be hard, and I'm kinda flabberghasted nobody is doing it. Well, at least in the sub-$1000 category. I mean, it's 2 SODIMMs, a AAA-NiCad battery, a PCI-E-DDR2 memory controller, a PCI-E to SATA6Gbps controller, and that's it. [Fred]: Agree. I am struggling so hard to procure that kind of device, but it is so hard to find for an individual. -- Erik Trimble Java System Support Mailstop: usca22-123 Phone: x17195 Santa Clara, CA ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
Re: [zfs-discuss] [ZIL device brainstorm] intel x25-M G2 has ram cache?
Erik Trimble wrote: Frankly, I'm really surprised that there's no solution, given that the *amount* of NVRAM needed for ZIL (or similar usage) is really quite small. a dozen GB is more than sufficient, and really, most systems do fine with just a couple of GB (3-4 or so). Producing a small, DRAM-based device in a 3.5" HD form-factor with built-in battery shouldn't be hard, and I'm kinda flabberghasted nobody is doing it. Well, at least in the sub-$1000 category. I mean, it's 2 SODIMMs, a AAA-NiCad battery, a PCI-E-DDR2 memory controller, a PCI-E to SATA6Gbps controller, and that's it. It's a bit of a wonky design. The DRAM could do something of the order 1,000,000 IOPS, and is then throttled back to a tiny fraction of that by the SATA bottleneck. Disk interfaces like SATA/SAS really weren't designed for this type of use. What you probably want is a motherboard which has a small area of main memory protected by battery, and a ramdisk driver which knows how to use it. Then you'd get the 1,000,000 IOPS. No idea if anyone makes such a thing. You are correct that ZFS gets an enormous benefit from even tiny amounts if NV ZIL. Trouble is that no other operating systems or filesystems work this well with such relatively tiny amounts of NV storage, so such a hardware solution is very ZFS-specific. -- Andrew Gabriel | Solaris Systems Architect Email: andrew.gabr...@oracle.com Mobile: +44 7720 598213 Oracle Pre-Sales Guillemont Park | Minley Road | Camberley | GU17 9QG | United Kingdom ORACLE Corporation UK Ltd is a company incorporated in England Wales | Company Reg. No. 1782505 | Reg. office: Oracle Parkway, Thames Valley Park, Reading RG6 1RA Oracle is committed to developing practices and products that help protect the environment ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
Re: [zfs-discuss] [ZIL device brainstorm] intel x25-M G2 has ram cache?
What you probably want is a motherboard which has a small area of main memory protected by battery, and a ramdisk driver which knows how to use it. Then you'd get the 1,000,000 IOPS. No idea if anyone makes such a thing. You are correct that ZFS gets an enormous benefit from even tiny amounts if NV ZIL. Trouble is that no other operating systems or filesystems work this well with such relatively tiny amounts of NV storage, so such a hardware solution is very ZFS-specific. No comment on how good or otherwise it is, but I just came across this: http://www.ddrdrive.com/ Which appears to be looking to provide something for OpenSolaris... (And some other minority interest OS called Windows). Julian -- Julian King Computer Officer, University of Cambridge, Unix Support ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
Re: [zfs-discuss] [ZIL device brainstorm] intel x25-M G2 has ram cache?
Yeah, If plus the ability to backup the data to the BIOS/EPROM on the motherboard, that should be the utmost solution…. From: Andrew Gabriel [mailto:andrew.gabr...@oracle.com] Sent: 星期一, 五月 24, 2010 18:37 To: Erik Trimble Cc: Fred Liu; ZFS Discussions Subject: Re: [zfs-discuss] [ZIL device brainstorm] intel x25-M G2 has ram cache? Erik Trimble wrote: Frankly, I'm really surprised that there's no solution, given that the *amount* of NVRAM needed for ZIL (or similar usage) is really quite small. a dozen GB is more than sufficient, and really, most systems do fine with just a couple of GB (3-4 or so). Producing a small, DRAM-based device in a 3.5 HD form-factor with built-in battery shouldn't be hard, and I'm kinda flabberghasted nobody is doing it. Well, at least in the sub-$1000 category. I mean, it's 2 SODIMMs, a AAA-NiCad battery, a PCI-E-DDR2 memory controller, a PCI-E to SATA6Gbps controller, and that's it. It's a bit of a wonky design. The DRAM could do something of the order 1,000,000 IOPS, and is then throttled back to a tiny fraction of that by the SATA bottleneck. Disk interfaces like SATA/SAS really weren't designed for this type of use. What you probably want is a motherboard which has a small area of main memory protected by battery, and a ramdisk driver which knows how to use it. Then you'd get the 1,000,000 IOPS. No idea if anyone makes such a thing. You are correct that ZFS gets an enormous benefit from even tiny amounts if NV ZIL. Trouble is that no other operating systems or filesystems work this well with such relatively tiny amounts of NV storage, so such a hardware solution is very ZFS-specific. -- http://www.oracle.com[cid:image001.gif@01CAFB70.D80EADB0]http://www.oracle.com/http://www.oracle.comAndrew Gabriel | Solaris Systems Architect Email: andrew.gabr...@oracle.commailto:andrew.gabr...@oracle.com Mobile: +44 7720 598213tel:+44%207720%20598213 Oracle Pre-Sales Guillemont Park | Minley Road | Camberley | GU17 9QG | United Kingdom ORACLE Corporation UK Ltd is a company incorporated in England Wales | Company Reg. No. 1782505 | Reg. office: Oracle Parkway, Thames Valley Park, Reading RG6 1RA [cid:image002.gif@01CAFB70.D80EADB0]http://www.oracle.com/commitmentOracle is committed to developing practices and products that help protect the environment inline: image001.gifinline: image002.gif___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
Re: [zfs-discuss] [ZIL device brainstorm] intel x25-M G2 has ram cache?
Yes. I mentioned this in my thread. And also I contacted Chris, ;-) -Original Message- From: zfs-discuss-boun...@opensolaris.org [mailto:zfs-discuss-boun...@opensolaris.org] On Behalf Of J.P. King Sent: 星期一, 五月 24, 2010 18:41 To: Andrew Gabriel Cc: ZFS Discussions Subject: Re: [zfs-discuss] [ZIL device brainstorm] intel x25-M G2 has ram cache? What you probably want is a motherboard which has a small area of main memory protected by battery, and a ramdisk driver which knows how to use it. Then you'd get the 1,000,000 IOPS. No idea if anyone makes such a thing. You are correct that ZFS gets an enormous benefit from even tiny amounts if NV ZIL. Trouble is that no other operating systems or filesystems work this well with such relatively tiny amounts of NV storage, so such a hardware solution is very ZFS-specific. No comment on how good or otherwise it is, but I just came across this: http://www.ddrdrive.com/ Which appears to be looking to provide something for OpenSolaris... (And some other minority interest OS called Windows). Julian -- Julian King Computer Officer, University of Cambridge, Unix Support ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
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
Re: [zfs-discuss] [ZIL device brainstorm] intel x25-M G2 has ram cache?
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
