Maximum dump size by tool
The dump size depends on the size of the system for which the dump is to be created.
All dump methods require persistent storage space to hold the kernel and user space of this system.
- kdump
- Initially uses the memory of the Linux® instance for which a dump is to be created, and so supports any size. A persistent copy can be written to any medium of sufficient size. While writing, the dump size can be reduced through page filtering and compression.
- DASD
- Depends on the disk size that is configured on the storage server. For example, you can use:
- 3390 DASD with 45 GB
- 3390 DASD with 1 TB
- Multi-volume DASD
- Can be up to the combined size of 32 ECKD DASD partitions. With the example DASD sizes of 45 GB
and 1 TB:
- 32 x 45 GB ≅ 1.4 TB
- 32 x 1 TB = 32 TB
- SCSI
- Depends on the capacity of the SCSI disk and which other data it contains. To write a large
memory dump to SCSI disk, you can use:
- z/VM® emulated FBA device that represents a real SCSI disk
- FBA disks can be defined with the CP command SET EDEVICE. These disks can be used as single-volume DASD dump disks. The SCSI disk size depends on your storage server setup.
- SCSI disk
- The SCSI disk size depends on your storage server setup. For SCSI dump partitions greater than 2 TB, you must use the GPT disk layout.
- NVMe disk
- For NVMe dump partitions greater than 2 TB, you must use the GPT disk layout.
- Channel-attached tape
- Depends on the tape drive. For example, IBM® TotalStorage™ Enterprise Tape System 3592 supports large dumps and also offers hardware compression. For large memory dumps, cartridges with up to 10 TB capacity are available.
- virsh dump
- Depends on the KVM host setup. The dump is written to a directory in the host file system. Size limits depend on the device that backs up this directory.
- VMDUMP
- Depends on the available spool space. The slow dump speed can lead to very long dump times for large dumps. Although technically possible, the slow dump speed makes VMDUMP unsuitable for large dumps.
- zgetdump live-system dump
- The dump can be written to any medium of sufficient size.