[zfs-discuss] ZFS, SSD mirror (without using whole disk)

fermulator fermulator at sympatico.ca
Sat Jan 16 07:42:24 EST 2016


Hey all,

I read here about ZFS's TRIM support on SSDs
http://www.open-zfs.org/wiki/Features#TRIM_Support

What I'm wondering is if we have a non-whole-disk utilization of ZFS on 
mirror pool consisting of 2x SSDs, can ZFS still issue TRIM commands to 
the underlying device?
The SSDs are older, so I'm concerned about maintaining the health of the 
devices.

For example, consider if we were running the root filesystem on ZFS 
mirror SSDs; this site does not currently discuss booting from 
whole-disk root volumes:
https://github.com/zfsonlinux/pkg-zfs/wiki/HOWTO-install-Ubuntu-14.04---15.04-to-a-Native-ZFS-Root-Filesystem
so, at the moment, I've setup my root volume with a sliver for boot, the 
rest for ZFS... bad idea?

$ sudo zpool status
   pool: zfsmain
  state: ONLINE
status: Some supported features are not enabled on the pool. The pool can
     still be used, but some features are unavailable.
action: Enable all features using 'zpool upgrade'. Once this is done,
     the pool may no longer be accessible by software that does not support
     the features. See zpool-features(5) for details.
   scan: none requested
config:

     NAME STATE     READ WRITE CKSUM
     zfsmain ONLINE       0     0     0
       mirror-0 ONLINE       0     0     0
         ata-KINGSTON_SNV425S264GB_07MA20034453-part1 ONLINE       0     
0     0
         ata-KINGSTON_SNV425S264GB_07MA20035331-part1 ONLINE       0     
0     0

errors: No known data errors

   pool: zstorage
  state: ONLINE
   scan: none requested
config:

     NAME STATE     READ WRITE CKSUM
     zstorage ONLINE       0     0     0
       mirror-0 ONLINE       0     0     0
         ata-WDC_WD6400AAKS-00A7B2_WD-WCASY7751034 ONLINE       0     
0     0
         ata-WDC_WD6400AAKS-00A7B2_WD-WMASY5518479 ONLINE       0     
0     0

errors: No known data errors

$ sudo gdisk /dev/disk/by-id/ata-KINGSTON_SNV425S264GB_07MA20034453
GPT fdisk (gdisk) version 0.8.8

Partition table scan:
   MBR: protective
   BSD: not present
   APM: not present
   GPT: present

Found valid GPT with protective MBR; using GPT.

Command (? for help): p
Disk /dev/disk/by-id/ata-KINGSTON_SNV425S264GB_07MA20034453: 125045424 
sectors, 59.6 GiB
Logical sector size: 512 bytes
Disk identifier (GUID): 4E92D2E6-B310-4EC9-9652-319DC6336612
Partition table holds up to 128 entries
First usable sector is 34, last usable sector is 125045390
Partitions will be aligned on 2048-sector boundaries
Total free space is 2669 sectors (1.3 MiB)

Number  Start (sector)    End (sector)  Size       Code Name
    1            2048       125028351   59.6 GiB    8300 zfs
    2       125028352       125044735   8.0 MiB     EF02 grub

Command (? for help): q

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