Tim:
>>> Have we got to the stage where the default install options for
>>> Fedora work fine with a SSD, or should I be tweaking something?
Rick Stevens:
> For many users, LVM is somewhat irrelevant. I use LVM because I often
> end up expanding filesystems by adding PVs to the VGs the LVs are
> built on (lots of acronyms there!), but my use cases are outside the
> normal desktop users.
Yes, I think most users will only have a single drive. And if they do
add another drive, chances are that they don't want to pretend that
they're one bigger drive. Not to mention the fun and games of dealing
with a system when half of a large virtual drive dies and takes out all
your data.
> The "annoyances" when moving the drive to another system can be
> reduced by naming the LVs logically--typically I use the host name as
> part of the LV and VG names. Therefore if I have to move an LV from
> host "bigdog" to host "hamster" there's little chance of a name
> collision.
I've done that kind of thing in the past. But if you forget, name
clashes aren't insurmountable (pun intended), but a pain to have to
deal with. But even with unique naming, just mounting LVM is more
hassle than other schemes. You can't just double click on a drive icon
and have the system work it out for you, as if you'd plugged in a USB
stick. Or, at least on *my* system, that's never worked. I had to use
command line tools to discover the drive and the names of its parts,
then manually mount the volume then group as two more steps.
> My recommendations for SSD:
>
> Use ext4 filesystems (they don't poke the journal as much as
> JFS or Btrfs).
I went for EXT4 as being closer to what I'm familiar with. I think
only BTRFS and LVM were the other two options presented by the
installer.
> Reduce swappiness ("vm.swappiness=1" in /etc/sysctl.conf)
I'll have to look into that, I've read about it long ago, but forgotten
all about it. The quick summary on Wikipedia gives a small range of
example values, that does sound like it's at the extreme end, though I
don't know much actual difference 1 verses 10 versus 60 does.
On my system I have
cat /proc/meminfo
MemTotal: 4045280 kB
MemFree: 1792672 kB
MemAvailable: 2767436 kB
Buffers: 106176 kB
Cached: 1062820 kB
SwapCached: 0 kB
Active: 1410028 kB
Inactive: 572900 kB
Active(anon): 695352 kB
Inactive(anon): 163560 kB
Active(file): 714676 kB
Inactive(file): 409340 kB
Unevictable: 48 kB
Mlocked: 48 kB
SwapTotal: 8388604 kB
SwapFree: 8388604 kB
Dirty: 152 kB
Writeback: 0 kB
AnonPages: 813968 kB
Mapped: 377180 kB
Shmem: 44992 kB
Slab: 158444 kB
SReclaimable: 111848 kB
SUnreclaim: 46596 kB
KernelStack: 7952 kB
PageTables: 39580 kB
NFS_Unstable: 0 kB
Bounce: 0 kB
WritebackTmp: 0 kB
CommitLimit: 10411244 kB
Committed_AS: 4347292 kB
VmallocTotal: 34359738367 kB
VmallocUsed: 0 kB
VmallocChunk: 0 kB
HardwareCorrupted: 0 kB
AnonHugePages: 0 kB
ShmemHugePages: 0 kB
ShmemPmdMapped: 0 kB
CmaTotal: 0 kB
CmaFree: 0 kB
HugePages_Total: 0
HugePages_Free: 0
HugePages_Rsvd: 0
HugePages_Surp: 0
Hugepagesize: 2048 kB
DirectMap4k: 173696 kB
DirectMap2M: 4020224 kB
So I don't know what amount of using swap I need to be able to do.
> Put things that change a lot (swap, /var/log, /tmp) on rotating
> media or RAMdisk to reduce writes to SSD
I only have one disk in the system, so swap is on the SSD, I see the
system automatically set up a tmpfs for /tmp, and /var/log is just an
ordinary directory.
> Use fstrim periodically
That I've briefly looked at, and it's confusing as to whether it's
actually worth using it.
> And MOST important:
>
> Back the sucker up REGULARLY AND OFTEN! SSDs tend to die
> suddenly and typically without much warning and it's quite
> difficult (if not impossible) to recover any data on them.
I tend to not store important stuff on client computers. It makes
updating easier, and I can carry on working on stuff on any PC, rather
than be tied to the one I stored things on.
> I like SSDs. I like their speed. I don't trust them much with
> critical data.
This is the first time I've used one. I was very surprised by the 13
second cold boot up of the new installation. I haven't had a computer
come up that fast since my old Amiga 1200.
I wonder what the longevity is for SSDs that aren't being used (*),
compared to hard drives.
* Such as backing up something and putting the SSD on a shelf.
--
[tim@localhost ~]$ uname -rsvp
Linux 4.11.11-300.fc26.x86_64 #1 SMP Mon Jul 17 16:32:11 UTC 2017 x86_64
Boilerplate: All mail to my mailbox is automatically deleted.
There is no point trying to privately email me, I only get to see
the messages posted to the mailing list.
ZNQR LBH YBBX!
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