Shopping for an enterprise array? Let’s play 20 questions, Part 2

Here is the second batch of enterprise storage array questions you can ask prospective vendors. Of course depending on your specific requirements, you will likely have additional questions, and some in this list may not be relevant.

Array Partitioning (Virtual Arrays)

Note: Array partitioning is a fairly rare feature on arrays which let you chop up an array into smaller virtual arrays for the purpose of delegated administration. This could be useful for multi-tenant arrays where various business units have data stored on the same physical array but business policies require separate administrators manage their ‘slice’ of the array. Administrator “A” could be prohibited from even seeing LUNs or storage ports assigned to business unit “B”. Healthcare, financial, and Government industries come to mind.

1. Does the array support any type of array administrative ‘partitioning’?
2. How many partitions are supported, and what can you scope (physical disks, host ports, LUNs, general array config changes, replication sets, etc.)
3. Does it support role based administration for each partition?

WAN Data Replication

1. What type of data replication options does the array support? (Synchronous, asynchronous, periodic, etc.)
2. If 1K of data is changed, what is the smallest increment of data that is replicated?
3. Does the array have any replication de-duplication or WAN optimization built-in to minimize bandwidth usage?
4. Does the array support 1 to N, N to 1, or multi-hop data replication?
5. What protocols can be used for data replication (iSCSI, FC, FCP, etc.)?
6. If you reverse the replication roles, such as recovering from a disaster and failing back to the primary data center, is a full re-sync needed or can the array do delta syncs?
7. If the WAN link goes down between replication partners, how are incoming writes handled? Are they written to a journal, is write order preserved?
8. If a journal is used, is it stored in memory or on disk?
9. What happens if the journal wraps around?
10. Certified for use with any WAN optimizers (Riverbed, Cisco, etc.)?
11. How many replication consistency groups are supported per array and how many LUNs in each group?
12. Is concurrent bi-directional replication supported?
13. Can a volume be concurrently replicating and snapshot?
14. Can a read-write snapshot be replicated?
15. Can thin volumes be replicated?
16. What is the maximum number of mirror pairs?
17. Can mirror pairs use different RAID types? (Replicate RAID-1 volume to a RAID-5 volume)

RAID and Drive Intermix Support

1. Are there restrictions on mixing RAID levels within the array?
2. Are there restrictions on mixing drive types within the array? (FC, SATA, FATA, SAS, SSD)
3. What are the RAID types and disk group options? (RAID 1, 2+2, etc.)
4. Can you limit RAID groups to a specific set of physical disks?
5. Are any array functions limited during a failed drive rebuild?
6. Does the array use traditional RAID disk groups for storing data, or does it use virtual RAID where blocks of data are scattered throughout the array?
7. Can the array wide stripe a single LUN over dozens or hundreds of drives?
8. Does the wide striping require the use of meta-LUNs or require manual configuration?
9. If SATA drives are used, is any type of read after write required for data verification?

Data Integrity and Security

1. Does the array calculate end-to-end checksums for all data to verify integrity?
2. Does the array store any checksum data with each block that is verified on read/write?
3. Does the array have any type of data at rest encryption?
4. Background disk scrubbing/verification of data?
5. Data shredding/secure delete conforming to DoD standards?
6. Support SMART enabled disks?
7. Is the array compatible with NetApp Decru or Brocade SAN encryption devices?
8. Does the array support SSH for remote CLI control?
9. Has the array or software been common criteria certified?
10. Does the array have any FIPS certifications?

Installation and administration

1. Can the customer install, configure, and perform routine maintenance on the array?
2. Under what circumstances must a factory technician perform maintenance?
3. How much professional services are recommended for a typical installation?
4. Can all configuration be done via a GUI, or is command line/scripting needed?
5. Can the customer place the array into their own rack?
6. Can other equipment co-exist in your racks? (SAN switches, tape library, etc.)
7. Do you ever need to manually balance LUNs, host port assignment, controller ports, disk groups, etc. to ensure optimal and even performance?
8. Is there any support for ‘dark sites’ where a customer must do the install and all maintenance?
9. If the array is not connected to the internet, is there a stand-alone facility to alert operators on array failures or predicted failures?
10. Can the customer retain failed hard drives, and how does this impact the warranty?


1. Does the array support hot firmware updates?
2. What type of interruption is there during hot firmware updates? (ports taken temporarily offline, controller reboot, etc.)
3. Is data distributed such that an entire shelf/magazine failure would not cause data loss?
4. Target hardware availability (how many 9s)?
5. What type of internal redundancy is there?
6. What components can be replaced hot?

VMware ESX Integration

1. Does the array have an VMware ESX specific integration software/features, such as a vCenter snap-in?
2. Does the array support application aware (VSS) snapshot integration with VMware VMs?
3. Is the array certified for VMware SRM?
4. Any roadmap for value added features to vStorage?
5. If the array is ALUA, does it support ALUA round robin access with vSphere?
6. Are there any array specific vSphere multi-pathing add-ons or enhancements?
7. Does the array support NPIV?

Windows Server Integration

1. Hardware VSS provider (server 2003/2008 x64)?
2. MPIO driver (server 2003/2008 x64)?
3. When will server 2008 R2 be supported?
4. Does all of the management software support being installed on server 2008 x64?
5. Any type of advanced application recovery for SQL 2005/2008 and Exchange 2007?
6. Management packs for MS Operations Manager 2007 to support alerting on array hardware faults or performance warnings?
7. Does your management software support Windows AD authentication and support Windows groups for role based access?
8. Powershell interface?


1. Support SMI-S, if so, what version?
2. Upgrade path to next model? (forklift, in place, non-disruptive, etc.)
3. Any deep integration with a particular backup vendor? (Netbackup, CommVault, etc.)
4. IPv6 support for iSCSI or management?
5. What version of SNMP is supported?
6. If there’s an integrated service console, what OS does it run?
7. What type of power and outlets does the array require?
8. Built-in data deduplication?
9. Does the array support virtualizing external or third-party arrays?
10. Are there yearly software or hardware maintenance fees?
11. What are software licenses based on? (Capacity, per array, etc.)
12. Are there performance monitoring and alerting tools?

That wraps up my list of questions you can grill your storage vendor with. On the surface many arrays will appear to have the same or similar features but when you start to peel back the onion and dig deep into the array, you will often discover limitations. It’s important you discover these limits early on so you can decide which ones are show stoppers and which ones you can live with.

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