I resisted including this, because only one session can actually write to the volume, but many can read from it. This is mainly for restore performance. It still doesn't address the queueing issue. For sequential files, multi-session write access would introduce multi-plexed data streams. I much prefer migration from random access disk if the alternative is long-term storage in a multi-plexed format. (bad netbackup memories)
Backing up directly to sequential devices makes sense for large files/nodes. However, we have hundreds of machines that only back up a few GB per night. Random access disk is best for this. The "Max size threshold" is ideal for controlling this. I really believe the disk and file devices are complements and not competitors. I bet IBM is developing file devices heavily because it is relatively new and not mature. I don't believe they are trying to supplant disk devices. The real file-device competitor is VTL and those are the features that IBM is pursuing (deduplication, etc) I don't think random-access disk is going anywhere. Regards, Shawn ________________________________________________ Shawn Drew Internet t...@networkc.co.uk Sent by: ADSM-L@VM.MARIST.EDU 09/21/2009 11:51 AM Please respond to ADSM-L@VM.MARIST.EDU To ADSM-L cc Subject Re: [ADSM-L] the purpose of "file" device class Just to be uber-picky, FILE volumes now do allow multiple sessions/processes to read/write concurrently to a single FILE volume from TSM 5.5 onwards ( http://publib.boulder.ibm.com/infocenter/tivihelp/v1r1/topic/com.ibm.itsmms munn.doc/anrsgd5515.htm#wq28). The big picture as I've read it is that IBM are perhaps angling the user-base towards using FILE volumes, and that new developments would be implemented against FILE technology rather than DISK. That being said, it's fair to say that many people are simply more comfortable with the ease, simplicity and habit of implementing and managing DISK volumes. /DMc -----Original Message----- From: ADSM: Dist Stor Manager [mailto:ads...@vm.marist.edu] On Behalf Of Shawn Drew Sent: 21 September 2009 15:58 To: ADSM-L@VM.MARIST.EDU Subject: Re: [ADSM-L] the purpose of "file" device class Disk Based (Random access) lets you have several sessions all sending data to it. This removes the need to queue backups like all the competitors. But it will fragment as data expires and there is no defrag for random access. File devices (Sequential access) do also fragment over time, just like tape, but you are able to run reclamation on them. But sequential access would cause queuing. They each have different pro's and con's which make them suited for different tasks. (long term vs short term storage) Regards, Shawn ________________________________________________ Shawn Drew This message and any attachments (the "message") is intended solely for the addressees and is confidential. If you receive this message in error, please delete it and immediately notify the sender. Any use not in accord with its purpose, any dissemination or disclosure, either whole or partial, is prohibited except formal approval. The internet can not guarantee the integrity of this message. BNP PARIBAS (and its subsidiaries) shall (will) not therefore be liable for the message if modified. Please note that certain functions and services for BNP Paribas may be performed by BNP Paribas RCC, Inc. No virus found in this incoming message. Checked by AVG - www.avg.com Version: 8.5.409 / Virus Database: 270.13.109/2384 - Release Date: 09/20/09 06:22:00