Unity Whitepapers Flashcards
What are the first 4 drives in Unity?
system drives
What are system drives used for in Unity?
contain copies of data used by the OS
What are the limitations for Unity system drives?
can be used in Pools for user data
cannot be used as traditional hot spare for non-system drive
What is the minimum number of drives in a Unity XT?
5
How are system drives configured in Unity XT?
RAID 1/0 (2+2)
How many lanes are on the 12Gb SAS ports in Unity XT?
4-lane configuration
What is the front-end connectivity on Unity XT 380SPs?
2x CNA ports
What are the connectivity options for the CNA ports on Unity 380?
16/8/4GB FC
10GbE Optical SFP/TwinAx/1GbE
What is specific about CNA optical connectivity for Unity 380?
full iSCSI offload - relieves SP
What does Unity 380 XT have for management connectivity?
1GbE BaseT management port
1GbE service port
can be customized to match environment MTU
Where is the DPE connected to on Unity 380 XT ?
Bus 0
What is the M.2 drive used for in Unity SPs?
serves as backup device in the event of SP failure
memory contents of SP’s cache are written to Mi2 so it can be recovered once SP is restored
also holds boot image to run OS
What happens if their’s an SP and M.2 failure?
cache data can be recovered from the peer SP
How many cooling module failures can Unity XT SP handle?
single cooling module fault out of 5 per SP
if second module fails the SP will save cache content and shutdown to prevent overheating
What is the BBU in Unity XT?
provides power to SP if cabinet power is lost
What is something that is in addition to Unity XT 480 and higher SP models?
optional 4 port mezz card
25GbE Optical/10GbE BaseT
How is the DPE connected on Unity XT 480 and higher?
Bus 99
How is the first expansion port connected on Unity XT 480?
Bus 0
What are power supply options on Unity XT?
DC - 380/480
AC - all models
What are the DAE options on Unity XT?
25-Drive 2U DAE using 2.5” drives
15-Drive 3U DAE using 3.5” drives
80-Drive 3U DAE using 2.5” drives
What are the capacity options on UnityVSA?
10,25,50,350TBs
What is specific about Unity file data?
can make unified pool - don’t need to separate it out
What is required in Unity before creating a file system?
creation of a NAS Server
What is the makeup of a NAS Server in Unity?
each is logically separate - clients of one NAS can’t access data on another
What is true about link aggregation in Unity?
same speed
same duplex settings
same MTU size
When is link aggregation not supported on Unity?
not supported for iSCSI since multipathing is used for block access
What is fail safe networking (FSN) in Unity?
extends link failover into the network by supporting switch level redundancy
What is the relationship between link aggregation and FSN?
FSN provides extra layer of protection - link aggregation protects against port failure - FSN protects against full switch failure
What is the range of file system size in Unity?
3GBs - 256TBs
What do all thin file systems in Unity have regardless of size?
1.5GB reserved for metadata
all file systems in Unity thin by default - can make thick if want to
What is the default block size in Unity XT file systems?
8KB
What are the quota limits in Unity XT?
Soft limit (GB)
*Grace period (time)
*Hard limit (GB)
when soft limit is reached timer begins - if enough space isn’t reclaimed before timer runs out no new storage can be written to file system
What is 2 way vs 3 way NDMP?
2 way = file system backup that transfers data over FC directly to backup device - must use FC switch in between
3 way = file system backup that transfers backup data over network
What is MetroSync on Dell Unity XT?
ability to create remote synchronous replication sessions for file storage resources
NAS Servers
file systems
VMWare NFS datastores
What version of Unity doesn’t support synchronous replication?
UnityVSA (b/c it doesn’t have FC connectivity - synchronous replication based off first FC port on Unity)
What are the features of MetroSync on UnityXT?
snapshot replication
snapshot schedule replication
cabinet level failover
asynchronous replication to a third site
What is the benefit of snapshot schedule replication?
ensures destination system has same snapshot schedules applied as the source system in case of failover
What is cabinet level failover?
single command to initiate a simultaneous failover of all synchronously replicated NAS Servers and their associated file systems in parallel
should only be used when source system goes down
What can’t synchronous replication be used for in Unity XT?
local replication of file systems within same array
When is asynchronous replication used in Unity XT?
transporting data over long distances
replicate file resources locally between pools
How is asynchronous replication supported on Unity XT?
for file and block workloads and every model
What types of asynchronous replication are available on Unity XT?
one directional
fan-out
cascade
mixed
What is one-directional replication?
single resource replicating to a single destination resource
A →B
What is fan-out replication?
single resource replicating to up to four different destination systems
A →B and A →C
What is cascade replication?
single resource replicating to second system and from there replicating to a third system
A →B →C
What is mixed replication?
leveraging a combination of both cascade and fan-out or fan-out and cascade
A →B and B →C and B →D
What are proxy NAS servers in Unity XT?
ability to access all the file system/snapshot data on the destination NAS server through SMB and NFS
read only even if snapshot accessed is read/write =
When can proxy NAS servers be used on Unity XT?
works for both synchronous and asynchronous replication
for synchronous replication the destination file system isn’t fully mounted and not accessible
What are read/write SMB proxy shares on Unity XT?
ability to create SMB shares for writable and read only snapshots on the destination NAS server
designed to enable DR testing without any impact to ongoing replication session
works with both synchronous and asynchronous replication
What is file level retention (FLR) on Unity XT?
enables the ability to lock files - prevents them from being modified or deleted until a specific retention date
What systems does Unity XT support native file import?
VNX1 and VNX2
What is EMCopy?
command line tool developed by Dell for file data migration
What is Robocopy?
tool for performing Windows host based file replication
What is Rsync?
used to transfer file data for Linux users
What is PowerPath Migration Enabler?
migration tool for block data from legacy Dell systems
What Unity system doesn’t support data reduction?
UnityVSA (since data reduction requires write caching capabilities)
What is the required flash in a pool to enable data reduction?
more than 10%
What is the relationship between replication and data reduction on Unity XT?
asynchronous and synchronous operations support data reduction
both source and destination system can have it enabled/disabled
How does data reduction work on Unity XT?
data saved and written to system cache - write acknowledged w/ host
cache sends data to DR algorithm during flush and algorithm determines if savings are possible
space allocated on storage resource for data set - data saved to disk
What happens before data is sent to the data reduction algorithm in Unity XT?
first segmented into 8KB blocks
What happens in a read operation with data that has been reduced?
data must be recreated within System Cache in its original form so it can be sent to host
When can you enable data reduction on a storage resource in Unity?
at any time
What is Local LUN Move (aka Move)?
used to move data from a supported source Block resource to a target block resource within the same system
can be within the pool or between pools - between one data reduction pool and another non-data reduction pool
What is the relationship between data reduction and D@RE?
not impacted by D@RE as all data reduction operations occur on data residing in system cache before hitting backend disks
data decrypted before being sent to system cache in read operations
What is a thin clone?
read/write copy of a thin block storage resource that shares blocks with the parent resource
What are the drive partnership group rules?
same type drives but can be different sizes (SSD Flash 3 600GB can go with SSD Flash 3 1.6TB)
in spinning disk - different RPMs get put in different partnership groups (10Ks separated from 15Ks even if same size)
different flash types are in separate drive partnership groups
what is the max number of drives in a drive partnership group?
64
what is the mininimum number of drives in a drive partnership group based on?
RAID type + stripe width
What happens when a drive partnership group is full?
another minimum number of drives is needed to create the next drive partnership group with the same RAID type and stripe width
What are drive extents and what determines there size?
portion of a drive GBs in size - either for user data or spare space
determined by drive type (EX: all SSD Flash 3 drives have same size extents but 400GB drive has less extents of that size than 800GB size)
What is the order of creation in Unity Dynamic Pools?
drive partnership group
drive extent
RAID extent
private RAID group
private LUN
What is the minimum number of drives in a RAID 5 dynamic pool?
6 (4+1) + 1 hot spare
What is the minimum number of drives in a RAID 6 dynamic pool?
7 (4+2) + 1 hot spare
What is the minimum number of drives in a RAID 1/0 dynamic pool?
3 (1+1) + 1 hot spare
What is the spare drive rule in Unity XT?
1 per 32 OF A GIVEN TYPE
EX:
9x 600GB SAS 15K
9x 1200GB SAS 10K
9x 1800GB SAS 10K
3 total spares:
1x 600GB SAS 15K
1x 1200GB SAS 10K
1x 1800GB SAS 10K
27x 1200GB SAS 10K
1 total spare:
1x 1200GB SAS 10K
For what Unity XT features are thin storage objects recommended?
data reduction
snapshots
thin clones
asynchronous replication
What is SAN Copy?
provides one time migration of block resources from a third party array over iSCSI or FC
What is the relationship between RAID and pool tiers?
single RAID protection chosen for each tier
once RAID protection is selected and pool created the RAID protection can’t be changed
What are the performance metrics of the extreme performance tier in Unity XT?
user response = less than 1 - 5 milliseconds
multi-access response = less than 10 milliseconds
What are the performance metrics of the performance tier in Unity XT?
user response = 5 milliseconds
multi-access response = 10 - 50 milliseconds
What are the performance metrics of the capacity tier in Unity XT?
user response = 7-10 milliseconds
multi-access response = less than 100 milliseconds
How do capacity (NL-SAS) drives handle large block IO?
leverages system cache for sequential and large block IO
more efficient servicing
What are the strengths of the extreme performance (flash) drives in FAST VP?
extremely fast access for reads
handles multiple sequential workloads better than SAS or NL-SAS
What are the strengths of the SAS/NL-SAS drives in FAST VP?
sequential reads leverage prefetching of data
sequential writes leverage system optimizations favoring drive
What should you keep in mind with flash drives in FAST VP?
writes perform slower than reads
heavy concurrent writes affect read performance
single threaded large sequential IO performance equivalent to SAS
What should you keep in mind with NL-SAS drives in FAST VP?
long response times typically seen for heavy write workloads
How is data sliced up in FAST VP?
256MB slices
How is data sliced up in FAST CACHE?
64KB blocks
Where is the memory map located in Unity XT?
resides in DRAM memory and on system drives to maintain high availability
What is a FAST Cache promotion?
operation of copying data from spinning media to a location within FAST Cache
How is a read performed with FAST Cache?
IO request sent down
scans to see if its in system cache
not there - looks at memory map to see if its in FAST Cache
if not goes to down to drives - drives copy data to system cache for host to receive
How is a write performed with FAST Cache?
system cache receives write
held temporarily to see if memory map can locate a copy of the new write on FAST Cache
if it is it’s written directly to FAST Cache if not its sent to the drives and acknowledge by cache and host
What is page cleaning in FAST Cache?
occurs when FAST Cache needs to synchronize the contents of a page with the data’s location in the pool
done to reduce the number of dirty pages to give spare space
What are the drive sizes and number of drives needed for each Unity model for FAST CACHE?
Unity XT 380 400 GB 800 GB (4 Drives)
Unity XT 480 400 GB 1.2 TB (6 Drives)
Unity XT 680 400 GB 3.2 TB (16 Drives)
Unity XT 880 400 GB 6 TB (30 Drives)
What is the operational difference between FAST Cache and FAST VP?
frequently accessed data on spinning drive is COPIED to FAST Cache
data is PHYSICALLY MOVED between pool tiers in FAST VP
What is the timing difference between FAST Cache and FAST VP?
FAST Cache is always active
FAST VP relocation occurs during user specified relocation window
Where is system cache positioned vs FAST Cache?
system cache = closest to CPU / lowest latency
FAST cache = between system cache and pool drives
What is system cache best suited for?
sequential IO
IO larger than 64KB
zero fill requests
high-frequency access patterns
What is FAST Cache best suited for?
random IO
IO smaller than 64KB
data with a high locality
What is the size difference between system cache and FAST cache?
fixed 8KB page size (system cache)
fixed 64KB page size (FAST cache)
What is the availability difference between FAST Cache and system cache?
contents of system cache are volatile - BBU powers system in failure until all dirty pages copied to the mSATA drive
contents of FAST Cache are non-volatile and can withstand power loss
What is Redirect on Write snapshots in Unity XT?
after snapshot is taken new writes to snapped storage resource to the primary storage are redirected and written to a new location within the storage pool
What is benefit of Redirect on Write snapshots in Unity XT?
no need to define separate protection space or to copy data to a separate location before writing to snapped blocks
new data is simply written to a new location in the same pool
What is a consistency group?
allows admins to provision multiple LUNs within a crash consistent group which allow LUNs to be uniformly protected at same PIT
What is necessary for site to site replication between Unitys?
the source and destination storage resource must be of the same type:
LUNs
Consistency groups
VMware VMFS datastores
Thin clones
File systems and VMware NFS datastores
What are the replication options for synchronous replication on Unity?
one-directional
bi-directional
What is the relationship between VLANs and asynchronous replication?
can do replication interfaces on different VLANs for multi-appliance replication
What are the asynchronous replication types that are supported by Unity XT?
one-directional
bi-directional
one-to-many
many-to-one
What is bridged file replication in Unity XT?
A single file resource simultaneously replicating synchronously and asynchronously to two systems, while the destination system for the synchronous replication is also asynchronously replicating to a third system
What is the limitation of mixed file replication?
combination can be configured if each resource doesn’t exceed four total replication sessions
What is a limitation for any advanced file replication topology?
can’t configure a replication session to a resource that is already a replication destination for another resource
At what level is advanced replication topologies managed?
NAS Server level
What are the memory configurations for each model?
380 = 128GB
480 = 192GB
680 = 384GB
880 = 768GB
What are the FAST Cache configurations for each model?
380 = 800GB
480 = 1.2TB
680 = 3.2TB
880 = 6TB
