In this blog post we will cover the Vaulting technology related to the EMC Symmetrix V-Max and the DMX-4 technology. Vaulting is a key feature added on DMX-3 series of machines, which was further extended into the DMX-4’s and now the Symmetrix V-Max Systems. With power outages or major power fluctuations or other critical environmental conditions (temperature, water, fire and environmental hazards) in data centers, the vaulting technology saves all the data during the shutdown of the machine offering additional safety features with the customer’s data in transit (channels, cache — memory, etc).
Vaulting wasn’t available on the Symmetrix 3, 5 & 8 series of machines neither on the DMX nor the DMX-2 technology. With those machines, as a power hit, power fluctuation or environmental issue would be sensed; the BBU (battery backup unit) power would kick in keeping the machine in an online state for 3 minutes. During this time, all the I/O to and from the host is aborted; anything sitting in the cache is de-staged and written to disk drives. At that point, the entire machine goes into a DD (dead) state leaving itself offline (powered on but non-operational) or turning itself off if it’s a power outage.
With the DMX-3, DMX-4 and V-Max systems, since the number of cabinets has expanded; it becomes crucial that the data be saved before the Symmetrix turns itself offline or off. The concept of BBU has now changed to SPS (Standby Power Supply) modules that are locally attached to DAE’s (in Storage cabinets) and also in the System bay, that will keep the Symmetrix running for 5 minutes. During this time, the Symmetrix cuts off all I/O from the host, then lets the cache in the machine sync for consistency and then de-stage all the data from the cache — memory to the vault drives.
With the DMX-4 and V-Max as the memory is mirrored, it copies all the mirrored memory data to vault drives, creating literary two copies of the same data. In the later part of the blog post we will discuss what the rules of vaulting are and how is this technology deployed within the customers EMC Symmetrix storage environment.
The official definition of vault operation as referenced by EMC is: The vault operation is triggered when the Symmetrix system is powered down or transitioned offline or when environmental conditions initiate a vault situation.
During a power up procedure after the shutdown (vaulting), the hardware initializes and restores all the data in the cache – memory from the vault drives which verifies its integrity. Before another vault operation can be initialized, the SPS (Standby Power Supply’s) will have to be charged, which might take hours.
To read the blog post on EMC Serial Numbers, please see here
The following are the Vault requirements within the V-Max Systems
- Each director pair (2 — odd / even) on the V-Max system will require 200GB of vault space, that is 40 x 5GB chucks of dedicated vault data space
- The vault drives are M1 devices with not Raid or mirroring protection
- The vault drive cannot to be used by any host and is reserved for the Symmetrix
- Vault drives cannot be configured by Timefinder/Snap, virtual or dynamic sparing
- The data space created by the vault drives will be almost equivalent to the size of the cache — memory installed on the machine
- As mentioned in the previous blog post on enterprise flash drives, EFD’s cannot be used for vaulting operations
- For permanent sparing, 5 vault drives per loop are essential