Summary: FAST works on the storage group level, it means all your volumes can be located in a different pool in spite of their size or amount. For instance if FAST mechanism decided according skew to move 50% of extents of one volume to EFD and another part (50%) of that volume on SATA, it will work. So FAST looks on the storage groups and all extents within all volumes like one big entity with a lot of extents. That's why possible to have situation when only volume could be: - only on one pool (level) - on 1st and 3rd level (2 and 3, 1 and 2 too). So storage group for him is like one big volume.  In another hand, if space (on pool) is not enough for promotion/demotion of extents the FAST will keep trying to follow policy. In case if it is not able to follow policy (migrate groups of extents) it will stay as is (keep extents on old places and wait, when space will be enough for promote/demote). Also FAST looks on the response time of pool before moving of extents, for more information please read there: [URL]
Hello Experts! Could you please tell me how it can be according next output if we have the FAST policies like this: Policy A:    10% EDF - 10 % FC - 80% SATA Policy B:     15% EDF - 15 % FC - 70% SATA and output: [IMAGE] the device 09c1 and 061e are bound to SATA pool and as you can see the extents are allocated on SATA and EDF only? How is it possible? We have strong rules for FAST and as I understand all extent should be allocated according these rules: (for Policy A) - 10% extents should follow to EDF, 10% to FC and 80% to SATA respectively. On the screen shot I don't see allocation for FC pool at all. Could you please explain?  And one more question regarding pools and FAST. For instance we have 3 pools - EDF, FC and SATA. and free space on them EDF - 1 gb, FC - 5 gb and SATA - 100gb. and the same FAST policy - 10% EDF - 10% FC and 80% SATA. I bind new volume 100gb to FC pool (Max. Subscription limit allows me to do that and don't think about PRC for this example) and host does write to volume and within 10 min all 100 GBs have been written to volume. Of course almost all of extents will be written to SATA pool (am I right?) and then how the FAST will transfer extents if we have so strong policy? it can allocate 10 gb on EDF and 10 gb on FC pools, there are not enough space. which is the behavior of  FAST in this situation? Thank you!  Message was edited by: evgenym
How does FAST move the extent?