Adaptec Zero Maintenance Cache Protection in detail
Caches on RAID controllers accelerate write accesses. Without protection, however, cache content is lost in the event of a power failure. If the cache currently contains file system metadata, there is a risk that the entire contents of the file system will be lost due to the loss of the cache content.
In the past only BBUs were used for cache protection (see RAID Controller and Hard Disk Cache Settings and Battery Backup Unit (BBU/BBM) Maintenance for RAID Controllers. Adaptec offers an alternative solution with Zero Maintenance Cache Protection for Adaptec RAID Controller. In the long run, this solution is cheaper than a conventional RAID controller with the running costs of BBU maintenance.
MegaRAID controllers offer a similar technology with CacheVault.
How it works
With traditional RAID controllers, a BBU (Battery Backup Unit) protects the contents of the cache. The cache content is preserved because the cache modules are powered by the battery during a power outage. If the battery is empty (usually after 72 hours at the latest), the cache content is also lost.
ZMCP does not use a rechargeable battery. The cache content is protected by the following system:
- A double layer capacitor is connected to the RAID controller.
- This capacitor is fully loaded automatically during server startup.
- In the event of a power failure, the RAID controller uses the power of the capacitor to write the entire contents of the cache (512 MB or 1 GB, depending on the model) to a non-volatile flash memory (similar to a USB stick). Since 4 GB flash memory is usually the cheapest of the quantities produced worldwide, these are installed on the controller. But only 512 MB or 1 GB are needed.
Controller with ZMCP
Adaptec offers the following controllers with ZMCP:
Controller | ZMCP cache protection with |
---|---|
Adaptec SmartRAID 3162(-8i und -8i /e) Controller | ASCM-17F (ZMCP module and capacitor onboard)[1] (6th Gen ZMCP) |
Adaptec SmartRAID 3100 Controller | ASCM-35F (onboard ZMCP module with external capacitor)[1] (5th Gen ZMCP) |
Adaptec Series 8Z RAID Controller 12 Gb | AFM-700 (onboard ZMCP module with external capacitor)[2] (4th Gen ZMCP) |
Adaptec Series 8 RAID Controller 12 Gb | AFM-700[3] (3rd Gen ZMCP) |
Adaptec Series 7 RAID Controller 6 Gb | AFM-700 (3rd Gen ZMCP) |
Adaptec Series 6 RAID Controller 6 Gb | AFM-600 (2nd Gen ZMCP) |
Adaptec Series 5 RAID Controller 3 Gb | ZMCP (Adaptec Series 5Z models) |
Advantages
Adaptec ZMCP offers the following benefits:
- maintenance-free (no renewal of the BBU)
- permanent cache protection (BBU batteries hold data for max. 72 hours)
- less waste heat compared to the battery of a BBU
- lower costs over the lifetime of the server (no BBUs to purchase and replace)
Comparison ZMCP - BBU
The following table shows some differences between ZMCP and a BBU:
Property | RAID controller with ZMCP | RAID controller with BBU |
---|---|---|
Maintenance schedule |
|
|
Maintenance window |
|
|
max. reaction time in case of power failure to prevent data loss |
|
|
Charging time |
|
|
Time until cache protection is available |
|
|
Special requirements |
|
|
Disposal |
|
|
Further Information
- FAQs zu ZMCP (adaptec.com)
- The ABC of Zero-Maintenance Cache Protection (adaptec.com)
- Whitepaper: Adaptec Zero-Maintenance Cache Protection (adaptec.com)
- tweaktown.com: Adaptec Zero-Maintenance Cache Protection Explained (tweaktown.com)
References
- ↑ 1.0 1.1 Zero Maintenance Cache Protection (microsemi.com)
- ↑ Zero-Maintenance Cache Protection Technical Brief (microsemi.com)
- ↑ Adaptec Flash Module 700 Kit (AFM-700) 3rd Gen Zero-Maintenance Cache Protection (adaptec.com)