A few thoughts: Migrate/Archive The three purposes of HSM migration are to 1) compress the data so that the footprint is smaller, 2) move it to a lower cost media so that the TCO is lower and 3) move the data to an offline media that doesn't consume online UCBs. When considering bringing all of your data back online, you need to consider the impact of all three. 1) Assuming 3:1 compaction, you'll need 3x the online storage. With zEDC, that will vary on both what you can get on the primary storage and the ML2 storage. 3) For larger shops, the number on online UCBs is a factor. It's not a factor for smaller shops.
Some clients have selected to go to an all HSM ML1 environment to still get the advantage of zEDC compression on inactive data. (You may be utilizing zEDC for primary storage, but that is only available for nonVSAM data). These clients utilize the lowest cost disk and utilize the value of zEDC compression to minimize the footprint. Another thing to consider with an all disk environment is your 'relief valve'. It's simple to migrate data to tape as a means of ensuring that you always have enough space on your primary storage for growth. If you only have primary storage, what is your exception handling case when you have unexpected growth and no migration tiers to which to move your inactive data? How quickly can you bring more primary storage online? Another option is DS8000 transparent cloud tiering. This enables you to migrate inactive data to cloud object storage, with minimal cpu since the DS8K is doing the data movement. If not a primary means of migrating data, it is a very good option for a 'relief valve'. Backup Regardless of the replication technique that you are using (synchronous/asynchronous), you need point-in-time copies of your data for logical corruption protection. If a data set is accidentally or maliciously deleted, replication quickly deletes it from all copies. Also, if data becomes logically corrupted, it is instantly corrupted in all copies. So, you have to have a point-in-time backup technique for all of your data. You need as many copies as you want recovery points. One copy doesn't give you much security. Keeping n copies on disk can get pricey and consume alot of storage. Also, you need to replicate the n PiT copies to all of your sites so that you can do a logical recovery after a physical fail over. This makes the cost add up even more quickly. TCT is another good option for this. You can keep 1 or 2 copies on disk and then have HSM migrate/expire the older backup copies to cloud object storage which is then available at all of your recovery sites. Glenn Wilcock DFSMS Chief Product Owner ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN
