Specifications

Escala Tower PL & S, E, T System Hardware
Chapter 3: External Storage and SAN Subsystems 36/116
9es3s1c3.doc
Rev 5.9
02/12/2003
3.3. The 3.5" SCSI-2 Disk Modules
All DAS models support high performance 4.2GB (7200RPM), 8.8GB (7200RPM) and 17.8GB disk
drives. Up to 30 Winchester disk units can be configured in the 3000 Series, up to 20 disk units in the
2000 Series, up to 10 disk units in the DAS 1000 Series. The disks within the storage system can be
configured as either individual disks, RAID 0 groups, RAID 1 or RAID 1/0 pairs, RAID 3 or RAID 5
groups. Any or all of these modes of operation can be configured concurrently. This allows the tuning
of the DAS 1000, 2000 and 3000 Series to adapt to specific attributes of a given application.
A small amount of disk capacity will be used to save the write cache when a power failure occurs.
Each disk drive is housed in a hot plug disk module. Each module consists of a disk drive, a drive
carrier, and a regulator PCB. In redundant RAID configurations, when a disk failure occurs, any
module can be removed from a logical group without halting operation of the array. When drive
replacement is done, data is automatically rebuilt on the new disk.
On redundant RAID configurations global sparing is another area where the DAS 1000, 2000 and
3000 Series offers significant benefit. Global sparing allows the user to designate one or more spares
which will satisfy the requirements of any redundant logical group within the subsystem. By initiating
a rebuild on the global spare, the disk array essentially heals itself; thereby re-establishing disk level
redundancy, minimizing the impact of degraded mode operation, and minimizing exposure to double
failures within a single group.
Manufacturers specify disk capacities in GB. One gigabyte (GB) is 1,000,000,000 bytes (ten to the
ninth). Under AIX, volume sizes are given in MB (two to the twentieth) with the convention: one MB
is 1024 x 1024 bytes. A 5-percent difference in size appears between both measurements of the same
space. For example a 4.2 GB disk (4.2 x 10**9 bytes) will be viewed as a 4,091 MB volume at AIX
level.
3.4. The DAS 3000 Series Cabinet
DAS3500 discontinued as of 30 June 1999.
DAS3200 discontinued as of 30 September 1999
The DAS 3000 deskside cabinet includes space for 5 to 30 replace-under-power (hot plug) disk drives,
two Storage Control Processors, one mid-plane, three DC power supplies, and one cooling assembly to
support the array's operation and replace-under-power features. DAS3200/DAS3500 cabinets manage
room for a Battery Backup Unit for write cache security.
Hot plug technology results in dynamic expansion ability. Users can expand capacity or add any other
component while the system remains on line and operating.
There is no difference between the cabinet models.
The DAS3500 subsystems is connected to the host either via a copper connection (limited to 30
meters) or via an optic fiber connection using an Media Interface Adapter (MIA) depending on the
distance between the Host and the DAS3500.
The distance is up to 10Km by using Link Extender box and suited optic fiber connection (9µ).