HP A3550A - High Availability Disk Arrays Model 20 Storage Enclosure User Manual page 341

SIMM Removal and Replacement
Note SIMMs must be equal in capacity and installed in pairs.
Caution Strap the ESD wrist strap to your wrist and ground it to the disk array chassis (or
suitable ground). Place the SIMMs on an ESD conductive sheet when they are
removed from their packaging. Use ESD kit P/N 5182-4119 (supplied with each array).
Caution In a single-SP configuration, data will be lost if the SP is not disabled and the unposted
data is not written to disk before the SP is removed. In a two-SP configuration, the data
is mirrored so the data is preserved. Hewlett-Packard recommends that the cache be
disabled before an SP is removed.
SIMM Removal and Replacement 7-17