ZFS OpenZFS L2ARC on a budget

In April last year, I began using low-end flash (USB thumb drives) as L2ARC for a notebook with 16 GB memory. Very pleasing.



Yesterday, I got an older notebook with 4 GB memory. An opportunity to tell whether a similar approach will be worthwhile.

Early observations, with the cache device more than half full:

2022-06-12 19-29-29.png 2022-06-12 19-30-29.png

Code:
last pid:  2429;  load averages:  0.12,  0.08,  0.07; battery: 100%     up 0+00:48:38  20:07:06
36 processes:  1 running, 35 sleeping
CPU:  1.3% user,  0.0% nice,  1.2% system,  0.2% interrupt, 97.3% idle
Mem: 100M Active, 124M Inact, 1561M Wired, 1968M Free
ARC: 920M Total, 518M MFU, 13M MRU, 4096B Anon, 83M Header, 305M Other
     370M Compressed, 1007M Uncompressed, 2.72:1 Ratio
Swap: 16G Total, 16G Free

  PID USERNAME    THR PRI NICE   SIZE    RES STATE    C   TIME    WCPU COMMAND
 2227 sddm         16  20    0   321M   118M select   1   0:06   0.00% sddm-greeter
 2214 root          5  20    0   117M    43M select   0   0:02   0.00% Xorg
 2212 polkitd       7  27    0  2147M    24M select   1   0:00   0.00% polkitd
 2230 root          7  52    0    88M    18M select   1   0:00   0.00% bsdisks
 2194 root          2  52    0    71M    16M select   1   0:00   0.00% sddm
 2219 root          1  52    0    67M    16M select   0   0:00   0.00% sddm-helper
 2289 root          1  20    0    21M  9724K select   0   0:00   0.00% sshd
 2210 root         16  42    0    50M  8572K select   0   0:00   0.00% console-kit-daemon
 2156 root          1  20    0    21M  8444K select   1   0:00   0.00% sshd
 2233 root          4  20    0    35M  7644K select   1   0:00   0.00% upowerd
 1868 root          1  20    0    19M  7552K select   0   0:00   0.00% zfsd
 1694 root          1  20    0    21M  7396K select   0   0:00   0.00% wpa_supplicant
 2171 root          1  20    0    18M  7140K select   0   0:00   0.00% sendmail
 2174 smmsp         1  20    0    18M  6700K pause    1   0:00   0.00% sendmail
 2120 ntpd          1  20    0    21M  6656K select   1   0:00   0.00% ntpd
 2220 sddm          1  52    0    17M  4512K wait     0   0:00   0.00% ck-launch-session
 2292 root          1  20    0    14M  4308K pause    0   0:00   0.00% csh
 2074 messagebus    1  20    0    14M  4012K select   1   0:00   0.00% dbus-daemon
 2226 sddm          1  49    0    14M  3636K select   1   0:00   0.00% dbus-daemon
 2429 root          1  20    0    14M  3440K CPU1     1   0:00   0.00% top
 2225 sddm          1  52    0    13M  2856K wait     0   0:00   0.00% dbus-run-session
 1808 _dhcp         1  28    0    13M  2816K select   1   0:00   0.00% dhclient
 2021 root          1  20    0    13M  2748K select   1   0:00   0.00% syslogd
 1746 root          1   4    0    13M  2708K select   0   0:00   0.00% dhclient
 1743 root          1  23    0    13M  2636K select   0   0:00   0.00% dhclient
 2159 root          1  20    0    13M  2536K nanslp   0   0:00   0.00% cron
 2200 root          1  52    0    13M  2248K ttyin    0   0:00   0.00% getty
 2206 root          1  52    0    13M  2248K ttyin    0   0:00   0.00% getty
 2204 root          1  52    0    13M  2248K ttyin    0   0:00   0.00% getty
 2202 root          1  52    0    13M  2248K ttyin    0   0:00   0.00% getty
 2203 root          1  52    0    13M  2248K ttyin    1   0:00   0.00% getty
 2205 root          1  52    0    13M  2248K ttyin    1   0:00   0.00% getty
 2207 root          1  52    0    13M  2248K ttyin    1   0:00   0.00% getty
 2201 root          1  52    0    13M  2248K ttyin    1   0:00   0.00% getty
 1501 root          1  52    0    12M  2072K pause    0   0:00   0.00% adjkerntz
 1809 root          1  20    0    11M  1540K select   0   0:00   0.00% devd

Over the next few days I'll occasionally use Firefox, Dolphin and so on, to begin gaining a sense of how it feels after what's in L2ARC is a truer reflection of everyday desktop stuff …
 
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