A new snapshot of a storage volume is created by suppressing write requests. Once pending write requests from the computing nodes are completed, storage nodes create a new snapshot for the storage volume by allocating a new segment to the new snapshot. Subsequent write requests to the storage volume are then performed on the segments allocated to the new snapshot. A block map records segments where current data for an LBA of a slice of a storage volume is stored. Block maps may be written to a storage device in order to free memory. Block maps may be read back into memory when needed. Writing and reading of block maps may be performed upon fragments of block maps. On restarting of the storage node, block maps may be restored from block maps stored in the storage device.