This is good idea but I think there are other aspects to take into account: - in case of RAID array failure you should have a copy pool to restore. You can make file copypool but you cannot send disks off-site so easy. And how to perform reclamation of off-site disks! So complete avoidance of tapes will be hard. - price of the library itself is high but later price on cartridges is not. Tape storage is still cheaper. LTO cartridge will hold 100GB uncompressed data, with compression is more. Two 73 GB disks or one 180 GB for the same capacity would weight over $1000. - you forget to take into account the electricity (V * A = W, W * h = $). If you have to hold the backups for a month or a quarter calculate the power consumption too. It is approx. 0.5W/GB so for 4 TB you will have more than 2kW only from disk. And if you have to keep 2 or 5 year archives ... - if disk extension is easy for you, tape is easier. Add new disk, (re)build RAID array, define raw volume or filesystem, define TSM pool/volume vs. checkin as scratch. And occasionally hot-swap bays will be short - new enclosure to be delivered, cabling, maybe new adapter and even someday new cabinet, etc. - think about growth rate of data being backed up. Disk pool does not have overflow location. For a small shop this might be very good solution. However data tends to grow very fast. Calculate "what-if" scenario for buying library now and if you buy it after a year or two. For sure you will be forced to do it.
Zlatko Krastev IT Consultant "Rooij, FC de" <[EMAIL PROTECTED]>@VM.MARIST.EDU> on 11.01.2002 09:04:45 Please respond to "ADSM: Dist Stor Manager" <[EMAIL PROTECTED]> Sent by: "ADSM: Dist Stor Manager" <[EMAIL PROTECTED]> To: [EMAIL PROTECTED] cc: Subject: TSM, extending backup storage Question: I think about a huge diskpool without migration to tape. Is there a limitation on the size of the diskpools? If not, are there things I have not thought about? The backup-service is separated from the original data by a dedicated building located 1 Km away from the original! I think we have a lot of benefits: * quicker restores * no waiting for the availability of tapeunits * less administrative overhead * migration from disk --> tape * no reclamation * less processor use * the admininistrative window will decrease, so the backup window can increase * no ATL * No tape-units * Easy exctending of storage capacity * ...........? I am aware this is a strange idea, but why not? with regards, Fred de Rooij Corus Information Services - Enterprise Services % +31 (0) 251 492215 - Fax : +31 (0) 251 471153 Email: [EMAIL PROTECTED]
