Al, Thank you very much for your comprehensive response. I am currently in the process of trying to Disable Write Cache. I have managed to do it via the Adaptec Software but for some reason windows still states that it is enabled.
I go into System manager - Devices - Hard Disks - Properties. In the properties I select Disk Properties and there is a tick next to Write Cache Enabled. I remove the tick and save and then go back in and the tick is still there. Any ideas? If you need more info I will supply what ever is needed. Rodney -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Mulnick, Al Sent: Wednesday, 3 November 2004 1:12 AM To: [EMAIL PROTECTED] Subject: RE: [ActiveDir] Write Cache Enabled http://www.webopedia.com/TERM/d/disk_cache.html is a reference for what it is. Disk cache is a very dangerous thing when it comes to JET DB technology. The reason is that if the disk device loses power, or corrupts before it can commit to media, then you lose that bit of data likely corrupting the db. If the db is not so far gone that it can't replicate, your problems get worse. You should see SAN implementations of DC's and the conversations it generates ;) On-disk caching is a way for vendors to squeeze a little more speed out of the platters. Consider two 15K scsi drives. One provides 10us write commit time (for example) while the other provides 2us write commit time. The difference? Cache. If you can commit to cache vs. the platter, it's much much faster as you buffer the writes until the platter is in an optimal position to write to media. Great for applications that are random r/w types with heavy or equal write signatures i.e. file and print applications or presentation applications. JET db technology can be very disk IO intensive. That's because it's a two-phase commit database technology; a good one too. But as you scale the database you tend to have more disk activity as more and more transactions take place. Microsoft has gotten quite good at figuring out what works and what doesn't and one thing they've learned is when to use JET DB technology; a typical JET db deployment is likely to be more read-intensive than it is write intensive. A good application for JET technology is something that has at least a 2.5 or 3:1 read/write signature. The more read-intensive, the more likely that JET technology will be a good fit. Sound like an application you're familiar with? LDAP is a read-intensive application by design and great read response is required to scale it successfully. Active Directory would be an example of a LDAP database that needs great read performance with some write performance. Some implementations of LDAP have adapted other db technology, such as DB2, Oracle, etc. to house their LDAP data stores. Microsoft chose their JET (JET Blue if I recall correctly, but don't quote me)engine. Since JET DB applications tend to be very read-intensive, the risk/reward of disk cache is not in your favor. Your better bet is to give the application the amount of spindles required to gain the IOPS needed to satisfy the performance needs of your application. In the case of Active Directory, separate the IO types to gain better performance (sequential IO on one set of dedicated spindles being your biggest performance booster) etc. Don't be fooled by the use of battery backup technology. It's not worth it and it usually comes on the array controllers only not on the disk device itself. The array controller battery backup is intended to protect against power failures when data is in the array cache, which of course is there to provide better performance. But the cache is considered flushed when the controller receives a successful commit response from the disk device. The disk device will send a positive response when you write to it's cache. It's at that point that you tend to be vulnerable to problems (i.e. corruption) for very little performance gain. Turn off the disk caching and you'll barely notice a difference if you've laid out your disk appropriately for your implementation. But you'll greatly reduce your risk. Microsoft knows what they're doing when they suggest you turn it off, trust me on that. al -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Rodney Gardiner Sent: Monday, November 01, 2004 6:46 PM To: [EMAIL PROTECTED] Subject: [ActiveDir] Write Cache Enabled I keep getting an error on one of our DC's stating that Write Disk Cache is enabled and if there is a system failure data corruption may occur. I have informed that this should not be enabled on a DC. I checked out Tech Net on the various errors I receive in the Event Viewer and it states generally the error can be ignored and that there is a hotfix that you must call Microsoft for to stop the error appearing. http://support.microsoft.com/default.aspx?scid=kb;en-us;830051 I was also informed that taking off the option for Write Disk Cache would have a big impact on the system performance. I understand it would have an impact but did not think it would be as big as I am being told. I was just after clarification as to whether it should be enabled on a DC or not. Any help would be appreciated. It is an SCSI Controller with Adaptec System SCSI Disk Device. It is the disk device that has Write Cache Enabled on it under its properties. Rodney -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of [EMAIL PROTECTED] Sent: Tuesday, 2 November 2004 10:16 AM To: [EMAIL PROTECTED] Subject: RE: [ActiveDir] locked out Rodney, this is a free download from ms under account management tools. Search under MS, you will find it. +---------------------------------------------------------------------+ Regards, Sandy Wu LADOTD IT. Tech. Support Office: (225) 379-1625 Hrs:6:30AM-3:00PM Central Time Email:[EMAIL PROTECTED] +---------------------------------------------------------------------+ Rodney Gardiner <rodney.gardiner@ vls.com.au> To Sent by: [EMAIL PROTECTED] [EMAIL PROTECTED] cc ail.activedir.org Subject RE: [ActiveDir] locked out 11/01/2004 04:16 PM Please respond to [EMAIL PROTECTED] tivedir.org Just curious as to where this lockedoutstatus.exe is kept? Rodney _____ From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Randy White Sent: Tuesday, 2 November 2004 7:31 AM To: [EMAIL PROTECTED] Subject: RE: [ActiveDir] locked out This is probably caused by a virus. Use lockedoutstatus.exe to find out what where the lock outs are originating. Then check the event log of that DC to find out the perpetrating computer. _____ From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of [EMAIL PROTECTED] Sent: Monday, November 01, 2004 2:29 PM To: [EMAIL PROTECTED] Subject: [ActiveDir] locked out All gurus, Wonder if any of you have experienced this before. Suddently over the weekend, all domain accounts ( i mean all ) are locked out except the domain admin accounts. What could have caused this problem ? The only clue that I had is this is the week to change the summer time back but we had this done every year, had never had this issue before. Could this be a worm of some sort of virus. Looking into our security log it did not show me nything out of norm ( faild security , locked out has been turned on) Any suggestions will be appreciated. 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