Combination Chemotherapy, Total Body Irradiation, and Donor Blood Stem Cell Transplant in Treating Patients With Secondary Myelofibrosis

Inclusion Criteria: * Diagnosis of primary of secondary myelofibrosis with transplant indication by Dynamic International Prognostic Scoring System (DIPSS)-plus (\> intermediate-1) * Patients \>= age 50 must have a comorbidity score (hematopoietic cell transplant-comorbidity index \[HCT-CI\]) \< 4 (Sorror) * Patients can be in chronic phase (CP) with bone marrow (BM) blast count =\< 15% as long as no evidence of disease acceleration per principal investigator (PI) and treating physician's opinion or after progression to acute myeloid leukemia (AML) and achieved =\< 5% BM blasts (morphologic complete remission \[CR\] prior to transplant) * Lack of an human leukocyte antigen (HLA) matched donor or need to proceed fast to transplantation when a patient does not have an immediately available matched unrelated donor (typed by high-resolution in the registry) * Performance status \>= 70% (Karnofsky); patients \> 50 years should have adequate cognitive function; any concerns regarding cognitive function should be addressed by a geriatrician/neurologist * Alanine aminotransferase (ALT)/aspartate aminotransferase (AST)/bilirubin =\< 5 X upper limit of normal (ULN) * Measured creatinine clearance \> 60 mls/min * Left ventricular ejection fraction (LVEF) \>= 50% * Corrected carbon monoxide diffusing capability (DLCOc) \>= 50% * No active infections * Prior treatment with JAK2 inhibitor therapy is not excluded; a JAK2 inhibitor will need to be stopped 1-2 days prior to starting conditio…