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		<title>Data Domain: The new CAS on the block?</title>
		<description>Discuss Data Domain: The new CAS on the block?</description>
		<link>http://www.backupcentral.com/mr-backup-blog-mainmenu-47/13-mr-backup-blog/140-dd-cas.html</link>
		<lastBuildDate>Fri, 10 Feb 2012 11:15:53 +0000</lastBuildDate>
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			<title>Not if you\'re CAS</title>
			<link>http://www.backupcentral.com/mr-backup-blog-mainmenu-47/13-mr-backup-blog/140-dd-cas.html#comment-145</link>
			<description><![CDATA[If you're CAS, you're de-duping at the object level, not at the sub-object level. Period. It's where the name came from. Each object is given a single address (i.e. MD5 or SHA-1 hash) based on its content, and is therefore forever referenced using this address. Hence the name, Content Addressable Storage.]]></description>
			<dc:creator>cpreston</dc:creator>
			<pubDate>Thu, 04 Oct 2007 10:34:28 +0000</pubDate>
			<guid>http://www.backupcentral.com/mr-backup-blog-mainmenu-47/13-mr-backup-blog/140-dd-cas.html#comment-145</guid>
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			<title>grammar says:</title>
			<link>http://www.backupcentral.com/mr-backup-blog-mainmenu-47/13-mr-backup-blog/140-dd-cas.html#comment-144</link>
			<description><![CDATA[I agree that that EMC chose to make their API hard when they didn't need to, but the point of my question was that I had understood their (flimsy) technical justification for doing so was precisely that they were hashing at the block level, rather than the object level. Are they not? (Is anybody? I haven't followed the market because it's not something anybody I've worked for has needed.)]]></description>
			<dc:creator>grammar</dc:creator>
			<pubDate>Thu, 04 Oct 2007 09:10:31 +0000</pubDate>
			<guid>http://www.backupcentral.com/mr-backup-blog-mainmenu-47/13-mr-backup-blog/140-dd-cas.html#comment-144</guid>
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			<title>You were misled</title>
			<link>http://www.backupcentral.com/mr-backup-blog-mainmenu-47/13-mr-backup-blog/140-dd-cas.html#comment-140</link>
			<description><![CDATA[I'm not saying that that ALL CAS vendors bring to the table is file-level de-duplication. I'm just saying that their de-duplication is only on the object level. (An objectcan be a file, an email, etc. It's whatever the archiving vendor sends to them. ) They They do bring other things to the table. For example, your filesystem will not meet the WORM requirements of an archive system, allowing you to prove 7 years from now that the object/email/file you're presenting in court is indeed the object/email/file that was written 7 years ago. As to your comment on EMC waiting for the other vendors to catch up, I call BS. There were dozens of archiving and record management vendors around that already knew how to write to a filesystem. EMC could have created a filesystem interface, and all those vendors would have automatically been supported. But no. They created an API, and forced all these existing archiving vendors to program to that API if they wanted to be listed as supported apps on EMC's website. Then, after increased customer pressure, they added the filesystem API.]]></description>
			<dc:creator>cpreston</dc:creator>
			<pubDate>Wed, 03 Oct 2007 21:46:18 +0000</pubDate>
			<guid>http://www.backupcentral.com/mr-backup-blog-mainmenu-47/13-mr-backup-blog/140-dd-cas.html#comment-140</guid>
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		<item>
			<title>Wait wait wait</title>
			<link>http://www.backupcentral.com/mr-backup-blog-mainmenu-47/13-mr-backup-blog/140-dd-cas.html#comment-136</link>
			<description><![CDATA[You're telling me that people vending CAS actually think that they're selling me something worth my employer's dollars when they're hashing at the *file* level? First, that's absurd. I can present a file system that does that in Perl with minimal I/O overhead atop any FFS look-alike in a weekend hack. I'm not paying for that. Second, I don't believe that's actually what the serious vendors are doing. EMC, for example, started selling their CAS absent an actual FS for it, and waited for the OS vendors to catch up. As I understood it, they were hashing at least at the block level, if not doing so in finer grains. Was I misled?]]></description>
			<dc:creator>grammar</dc:creator>
			<pubDate>Wed, 03 Oct 2007 19:59:44 +0000</pubDate>
			<guid>http://www.backupcentral.com/mr-backup-blog-mainmenu-47/13-mr-backup-blog/140-dd-cas.html#comment-136</guid>
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