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3.7 (1) |
Written by Mike
May 14, 2008
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NexentaStor 2.1 introduces a new capacity licensing scheme. If your appliance's version is 2.0 or older, please refer to The Old Schema below.
Starting with the version 2.1, NexentaStor Enterprise Edition imposes a simple unified capacity based limitation - a limit on the total physical ("raw") storage space, excluding hot spares, log devices and cache devices.
For instance, let's say you have 8 (eight) 1TB drives. The following table illustrates a few possible examples of deploying these drives, and the resulting licensed capacity:
configuration
|
storage space counted towards license limit
|
1) single volume (ZFS pool) with no spares, cache or log devices |
8TB
|
2) multiple volumes with no spares, cache and log devices
|
8TB
|
3) single volume with 6 drives in a RAIDZ configuration and 2 hot spares
|
6TB
|
4) two volumes with 4 drives total in MIRROR configurations, 2 hot spares and 2 SSDs slogs
|
4TB
|
5) single volume with 4 drives in a RAIDZ2 configuration, 2 spares, 1 log and 1 cache device |
4TB
|
Therefore:
- ZIL slogs (a.k.a. log) devices, L2ARC (a.k.a. cache) devices, AND spare drives are NOT counted.
- Your appliance's licensed storage capacity is simply a sum of all ("raw") drive sizes, excepting logs, caches and spares.
- And finally, unlimited site license does not have any capacity limitation.
The Old Schema
Enterpise Editions of NexentaStor 2.0 and prior versions impose capacity based limitation - a limit on total storage space. On a technical level, total storage space is a sum of 'size' properties of all appliance's data volumes, as reported by ZFS 'zpool' command. The system volume is not included.
When choosing a particular license, please also take into account the fact that usable capacity is always less than the total capacity. In particular:
- Usable capacity of a non-redundant configuration is approximately a sum of all disk sizes. Note that a certain percentage of space will be utilized by ZFS metadata. Note also that using non-redundant configurations is not recommended.
- N-way mirror of disks size X each can hold X bytes. For instance, a mirror based on 3 disks (that is, a 3-way mirror) of size 500GB each can approximately hold 500GB. In other words, the maximum reported used size for this configuration will not exceed 500GB. The same comments wrt ZFS metadata apply.
- A raidz1 group of N disks size X each can hold approximately (N-1)*X bytes. For instance, a raidz1 based on three 500GB disks can approximately hold 1000GB or 1TB. User data on a raidz1 volume occupies exactly the space required for both the data and the parity. For instance, creating 1MB file in a (2 + 1) configuration will reflect itself as approx. 1.5MB of used storage. The same comments wrt ZFS metadata apply.
- A raidz2 group of N disks size X each can hold approximately (N-2)*X bytes. Same comments apply.
The following exampe shows 4 drives ~1.2TB size each, combined into one volume with total resulting capacity of 4.5T:
nmc$ show lun
LUN ID Device Type Size Volume Mounted Remov Attach
c3t0d0 sd4 scsi 1187.3GB tier2 no no DAS
c3t1d0 sd5 scsi 1187.3GB tier2 no no DAS
c4t0d0 sd19 scsi 1187.3GB tier2 no no DAS
c4t1d0 sd20 scsi 1187.3GB tier2 no no DAS
nmc$ show volume tier2 status
volume: tier2
state: ONLINE
scrub: none requested
config:
NAME STATE READ WRITE CKSUM
tier2 ONLINE 0 0 0
c3t0d0 ONLINE 0 0 0
c3t1d0 ONLINE 0 0 0
c4t0d0 ONLINE 0 0 0
c4t1d0 ONLINE 0 0 0
nmc$ zpool list tier2
NAME SIZE USED AVAIL CAP HEALTH ALTROOT
tier2 4.50T 3.98T 532G 88% ONLINE -
Second example shows a 40 drive volume (each drive ~0.5TB) based on 4 RAIDZ2 groups, each having 10 drives. (Only the first one of those 4 RAIDZ2 groups is shown here, to save space.) The total capacity of this configuration is 18.1T, as shown below.
nmc$ show lun
LUN ID Device Type Size Volume Mounted Remov Attach
c0t0d0 disk4 scsi 476.9GB tier2 no no DAS
c0t1d0 disk10 scsi 476.9GB tier2 no no DAS
c0t2d0 disk15 scsi 476.9GB tier2 no no DAS
c0t3d0 disk20 scsi 476.9GB tier2 no no DAS
...
...
NAME STATE READ WRITE CKSUM
tier2 ONLINE 0 0 0
raidz2 ONLINE 0 0 0
c0t0d0 ONLINE 0 0 0
c0t1d0 ONLINE 0 0 0
c1t0d0 ONLINE 0 0 0
c1t1d0 ONLINE 0 0 0
c5t0d0 ONLINE 0 0 0
c5t1d0 ONLINE 0 0 0
c7t0d0 ONLINE 0 0 0
c7t1d0 ONLINE 0 0 0
c8t0d0 ONLINE 0 0 0
c8t1d0 ONLINE 0 0 0
nmc$ zpool list tier2
NAME SIZE USED AVAIL CAP HEALTH ALTROOT
tier2 18.1T 9.96T 8.17T 54% ONLINE -
See also: