From mboxrd@z Thu Jan 1 00:00:00 1970 From: Yuriy Umanets Date: Tue, 19 Feb 2008 14:02:02 +0200 Subject: [Lustre-devel] storing SOM epoch in EA In-Reply-To: <47BABB01.8060402@sun.com> References: <47BAA607.1000600@sun.com> <47BAAF3F.6030301@sun.com> <200802191359.47379.vitaly@sun.com> <47BAB962.8010901@sun.com> <47BABB01.8060402@sun.com> Message-ID: <47BAC53A.2030106@sun.com> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: lustre-devel@lists.lustre.org Alex Zhuravlev wrote: > Yuriy Umanets wrote: > >> EA is separate block is evil. It makes things slow. >> > > we have fast EAs (stored in inode, this is why we make them large) for years. > Well, people used horses for ages but this did not stop them from building cars :) Guys, I gave you idea, not worse than using EAs. I will not insist it is great. If you can't estimate its value yourself, well, let it be. We have such a nice thing as IAM and you keep talking about EAs... Seriously, IMHO what is bad about EAs: 1. You need to control their size, you need to bother; 2. Large-fast inodes make create/lookup slow. You need to load this thing to memory after all. I think this is complement to additional seeks caused by IAM; 3. Storing epoch in EA makes you use this chain to access epoch: fid->inode->epoch (in EA), IAM makes it shorter: fid->epoch (in IAM); 4. Large inodes consume more RAM; 5. There others... but they are less related to technical downsides/advantages so I will omit them. Thanks. -- umka