We have a couple of DataDomain 580s here. If you look in the archives you will find my comments on the rate of compression we are getting and my impressions. As far as the "putting all your eggs in one basket" scenario, that always is the worst case scenario. In our situation, we have been using the DD for about 18 months and have had no loss of data. The systems are constantly running a "verification" that soak up all the free cycles to double-check that what it thinks is on disk is on disk. It seems to run all the time, but doesn't seem to interfere with the in-line compression going on or impact the speed of the backups in the middle of the night.
We have done 1 code upgrade and 1 hardware upgrade in the last 18 months that caused us to have to take downtime on the DD. Our first OS upgrade was done just a couple of months ago as they released a new version that was supposed to improve the speed of the systems anywhere from 50% to 100%. (I guess someone decided to take the extra "sleep" statements out of the code ;-}). We just took down the TSM servers for safety and then ran the command to upgrade. They predicted up to 2 hours, but it actually took about 25 minutes. As for the improvements, I can see the CPU having a much lower utilization rate than it did before, but I have not really precent-ified the improvements. Ben -----Original Message----- From: ADSM: Dist Stor Manager [mailto:ads...@vm.marist.edu] On Behalf Of Richard Rhodes Sent: Thursday, June 25, 2009 9:04 AM To: ADSM-L@VM.MARIST.EDU Subject: Re: [ADSM-L] Dedupe > I a dedup appliance, that is exactly what you don't have. The dedup > process guarantees that only one copy is kept of each unique block of > that data. If a given block of data is lost due to corruption or > failure of the media, then potentially all of the copies of a certain > file that contains that block of data will be lost. The people who are > designing these products, therefore, build their products to mitigate > this potential loss by: This is exactly what scares me about dedup - the unit of recovery. For our current (and foreseeable future) tape systems, the unit of loss and recover is a TAPE. With a VTL/dedup it's a much larger unit which is hard to define, but could be up to the entire appliance. A software bug could potentially take out not only a local appliance, but a replication target. When DataDomain was here a few weeks ago, I asked them if they have ever had a data loss event. They quickly replied "NO". I wish I knew whether to believe them - vendors do NOT like to acknowledge crashed systems. Another question I asked - Why would I EVERY have to take your system down? Their reply what that it takes about 2hr to perform a microcode load. Other than that, it should never have to come down. That then leads to a discussion of frequence of code releases and how quickly one must upgrade. (I don't remember their answer) There is a part of me that strongly wishes we had a VTL/dedup system, but another part is very happy to be sitting out this round with all the vendor consolidation and product changes. ( Note: I am a FIRM BELIEVER in the worse case scenario! ) Rick ----------------------------------------- The information contained in this message is intended only for the personal and confidential use of the recipient(s) named above. If the reader of this message is not the intended recipient or an agent responsible for delivering it to the intended recipient, you are hereby notified that you have received this document in error and that any review, dissemination, distribution, or copying of this message is strictly prohibited. If you have received this communication in error, please notify us immediately, and delete the original message.
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