Specifications
Escala Tower PL & S, E, T System Hardware
Chapter 3: External Storage and SAN Subsystems 42/116
9es3s1c3.doc
Rev 5.9
02/12/2003
3.14.3. RAID Group Binding Rules
RAID0: 3 to 16 drives per group (3 to 10 for DAS1300)
RAID1: always 2 drives per group
RAID1/0: 4 to 20 drives per group (4 to 10 for DAS1300)
RAID3: always 5 drives per group
RAID5: 3 to 16 drives per group (3 to 10 for DAS1300)
In a DAS1300, or in a DAS 2000 Series with more than 5 drives per group, a very small risk of single
point of failure exits at internal SCSI bus level.
When configured in RAID1 RAID3 or RAID5 an amount of capacity of one disk is used for redundant
data storage.
3.14.4. Number of Power Modules
DAS1300:
The second power supply is an option, power redundancy is only assumed with it. Add the second
power supply with 2SPs or with the cache option. NOEMIE will set the option as default. You may
remove it to get a lower price, but availability will become poor.
DAS2900 and DAS3200/DAS3500:
The third power supply will be delivered with every subsystem.
3.14.5. Number of Storage Processors (SP)
The second SP is recommended for higher availability (associated or not with the second SCSI
connection) and for performance over 10 drives.
For high availability, it is mandatory to have the mirrored cache option.
For DAS2900, the single SP configuration is able to manage up to 15 disks without internal I/O
saturation (short random I/Os).
3.14.6. Mirrored Cache
The mirrored cache option needs the dual SP configuration, 5 disk drives or more, and the Battery
Backup Unit. The memory modules are provided by pairs. Memory size is 32 or 64 MB per SP. A 2-
MB space will be reserved for internal use on the DAS1300. The DAS2900 and DAS3200/DAS3500
need a 4-MB reserved space.
3.14.7. Single Board Cache
The single board cache option is available in single SP configuration, 5 disk drives or more, and the
Battery Backup Unit. The memory size is limited to 32 MB for every model. A 2-MB space will be
reserved for internal use on the DAS1300. The DAS2900 and DAS3200/DAS3500 need a 4-MB
reserved space.