Top Document: comp.arch.storage FAQ 2/2 Previous Document: [3.1] Unitree {Brief} Next Document: [3.2] National Storage Lab {Brief} See reader questions & answers on this topic! - Help others by sharing your knowledge From: Hierarchical Storage Management (Note: this evaluation is old, and should be taken with a grain of salt. rdv, 3/96) (6/93) We just bought both last year. We bought an Epoch I with the 20 GB EO and 327 GB worm. We will be upgrading it to an Epoch II soon. We also bought Unitree from Titan to run on a Silicon Graphics server and hook up to the STK 3480 silo. We hope to add more silos eventually. Unitree is licensed based on storage capacity while Epoch is not. There may be an exception to this - STK just began reselling Epoch as the front end for their silos and I'm not sure how they handle licensing. My office mate and I (I handle Epoch, he handles Unitree) have enjoyed comparing the merits/demerits of each over the last year. Comparison in our case is slightly slanted due to the fact that the Epoch has optical disk while the Unitree system has 3480 tape - so some observations have more to do with media advantages/disadvantages. Unitree + Allows large files - can span volumes + Allows you to enlarge the cache easily, allows very large cache +- Unitree has replaced several UNIX utilities with their own (FTP, NFS and the file system). This allows certain features to work but is generally slower and disallows access to the archive when you are on the server itself - unless you NFS mount! + Allows deleted files to be saved for a specified time + Allows multiple copies of files to be kept + Data is copied to archive soon after creation + Unitree runs on several different platforms - Does not allow access to data until it is completely reloaded - Behaves poorly with small files (due to necessary overhead) - Unitree is licensed to several vendors, so versions differ - NFS access is so slow that we recommend it not be used for file transfer - only for ls and du, etc. Use FTP. - The Silicon Graphics version is still new and has some problems Epoch + Allows access to the data as soon as part of it is loaded + Company seems serious about reputation and support + The Epoch II is based on a SUN system, with few modifications + Data is copied to archive only when the cache space is needed + All native UNIX transfer methods work - NFS, FTP and RCP + Add on products greatly simplify backup and extend archiving features to other systems. - Deleted files are gone forever - Currently only available on SUN. This will change. - Cannot span volumes yet - limiting file size - Has the SUN limitation of 2 Gb per filesystem. This would be a bigger problem if you used it for a 3480 silo. {Note 2GB of Magnetic Disk limit, not the entire HSM store} - Behaves poorly with small files (due to necessary overhead) - Since inodes are kept on magnetic cache, you must take into account the maximum number of files you will ever need. - Since inodes are always on disk, certain disk operations can take forever since all inodes must be examined. - Enlarging a magnetic disk filesystem which has associated archive media requires you to offload all data and then reload it. If anyone has found another way, I would like to hear about it. {Others did offer some easier work-arounds} In all fairness to Titan, they have been addressing any problems and it has been improving. Epoch too plans to address some of their shortcomings. We are looking forward to growing with both products. The likelihood that the various flavors of Unitree will standardize depends on what happens with Discos. My guess is that some features/enhancements will be filtered back to the base product released by Discos. Bye... (bodoh@dgg.cr.usgs.gov, 152.61.192.66, Tom Bodoh, USGS/EROS Data Center, Sioux Falls, SD) User Contributions:Top Document: comp.arch.storage FAQ 2/2 Previous Document: [3.1] Unitree {Brief} Next Document: [3.2] National Storage Lab {Brief} Part1 - Part2 - Single Page [ Usenet FAQs | Web FAQs | Documents | RFC Index ] Send corrections/additions to the FAQ Maintainer: rdv@alumni.caltech.edu (Rodney D. Van Meter)
Last Update March 27 2014 @ 02:11 PM
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