FreeNAS/ZFS/FreeBSD and MX500 SSD's

Kilobyte Kid

FreeNAS/ZFS/FreeBSD and MX500 SSD's

Hello Forum members!



Some older IBM disk shelves (24 bays, SAS 6Gb/sec) this is connected (Multipathed) to a Dell server with a SAS 6Gb/sec HBA. 



The server is an older Dell R810(power monster) and has 4x older L7555 series CPU's(64 cores) and 64GB of RAM and runs FreeNAS 11.2(still RC). Connectivity is 4x bonded ethernet to a decent but older ex4200 Juniper switch, this hardly matters though since the upstream internet connectivity is less than a gigabit and would be traversing NAT anyway.


The storage pool configuration of SSD's

To maximized available space, we have chosen a raidz2 and plan to run regular scrubs on the array and presently have only 1 pool consisting of 12 disks:


pool: shelf_1_ssd

state: ONLINE

  scan: resilvered 16.0M in 0 days 00:00:01 with 0 errors on Sun Nov 18 08:48:03 2018



NAME                                            STATE     READ WRITE CKSUM

shelf_1_ssd                                     ONLINE       0     0     0

  raidz2-0                                      ONLINE       0     0     0

    gptid/6b2fc271-4a50-11e8-a291-14feb5caaa4f  ONLINE       0     0     0

    gptid/726d7488-4a50-11e8-a291-14feb5caaa4f  ONLINE       0     0     0

    gptid/7ba6fb1b-4a50-11e8-a291-14feb5caaa4f  ONLINE       0     0     0

    gptid/8593cc2b-4a50-11e8-a291-14feb5caaa4f  ONLINE       0     0     0

    gptid/903739ba-4a50-11e8-a291-14feb5caaa4f  ONLINE       0     0     0

    gptid/9aa9b1ef-4a50-11e8-a291-14feb5caaa4f  ONLINE       0     0     0

    gptid/a6111a5e-4a50-11e8-a291-14feb5caaa4f  ONLINE       0     0     0

    gptid/b3ec8b57-4a50-11e8-a291-14feb5caaa4f  ONLINE       0     0     0

    gptid/c3887ae0-4a50-11e8-a291-14feb5caaa4f  ONLINE       0     0     0

    gptid/d3c396f4-4a50-11e8-a291-14feb5caaa4f  ONLINE       0     0     0

    gptid/e38b32d5-4a50-11e8-a291-14feb5caaa4f  ONLINE       0     0     0

    gptid/f118f9e2-4a50-11e8-a291-14feb5caaa4f  ONLINE       0     0     0



Use Case/Purpose


What my family members and I are hoping to achieve is some small amount of general purpose file storage (maybe a TB at most) and the rest will be devoted to Plex and archiving our independent DVD's/Bluerays into a Plex instance for each of us.  This should provide the disk throughput easily for streaming up to 8-10 30Mbps streams (half the SSD bandwidth) and the 64 cores should provide enough transcoding ability for our needs.



Q: My understanding of the Active Garbage collection feature is that the drive needs to be powered on, but not currently in use (I'm not sure how the drive knows this, but I'm interested as I assume the PHY on the drive would have already negotiated a link speed? not sure).  If that is correct, I would need to boot the server and pause it at POST for some amount of time?

Q: Is there a single SMART attribute would tell me what wear level the SSD's are presently at? Here are the ones that are seen by smartctl on the host system:


1 Raw_Read_Error_Rate

5 Reallocated_Sector_Ct

9 Power_On_Hours

12 Power_Cycle_Count

171 Unknown_Attribute

172 Unknown_Attribute

173 Unknown_Attribute

174 Unknown_Attribute

180 Unused_Rsvd_Blk_Cnt_Tot

183 Runtime_Bad_Block

184 End-to-End_Error

187 Reported_Uncorrect

194 Temperature_Celsius

196 Reallocated_Event_Count

197 Current_Pending_Sector

198 Offline_Uncorrectable

199 UDMA_CRC_Error_Count

202 Unknown_SSD_Attribute

206 Unknown_SSD_Attribute

210 Unknown_Attribute

246 Unknown_Attribute

247 Unknown_Attribute

248 Unknown_Attribute


2 Replies

Re: FreeNAS/ZFS/FreeBSD and MX500 SSD's

202 is the percentage worn. If you use a SMART tool that supports the drive you will see useful descriptions for them all.


The drive being not in use means not busy as opposed to not having a 'connection'.  So since it's a NAS it'll presumably be on all the time and see periods of none use overnight?  The drives should be set to not power down to take advantage of this.


It also sounds like your usage will be primarily read only?  Both wear and the erase/rewrite slow down that garbage collection counters are due to writing.

Kilobyte Kid

Re: FreeNAS/ZFS/FreeBSD and MX500 SSD's

Thank you for the information!  Much Appreciated!