[QUOTE=ewmayer;525001]Speaking of raining hard, hurricane Dorian, now category 5 and the second-strongest Atlantic hurricane since 1950, is [url=https://www.aol.com/article/weather/2019/09/01/hurricane-dorian-strengthens-to-category-5-storm/23804896/]pounding the Bahamas[/url]. Besides 185mph sustained winds, "Over two or three days, the slow-moving hurricane could dump as much as 4 feet (1.2 m) of rain."[/QUOTE]

The governor of Florida [URL="https://www.foxnews.com/media/hurricane-dorian-florida-climate-change-rick-scott"]has this to say[/URL]:

[quote]"We know the climate's changing and we know our storms seem to be getting bigger," he said. "The last four years as governor, I had four of them. And now, we have them my first year out... we don't know what the cause is -- but we've got to react to it... We've put money into dealing with things like sea-level rise... we've got to continue to figure this out."[/quote]

More on the situation with the tides reinforcing the storm surge:

[url=https://www.treehugger.com/natural-sciences/what-king-tide.html]What is a king tide?[/url] | TreeHugger

Reading one of the Guardian stories on hurricane Dorian, I came upon mention of a Caribbean delegation viewing the devastation in the Bahamas. The leader of the delegation caught my eye.[INDENT][QUOTE]Our colleague Oliver Laughland is in Nassau as Bahamians grapple with the devastation Hurricane Dorian has brought to the country.
Laughland [URL="https://www.theguardian.com/world/live/2019/sep/05/hurricane-dorian-carolinas-latest-live-updates-bahamas-us?page=with:block-5d714f768f08143ee1ae0e09#block-5d714f768f08143ee1ae0e09"]reports[/URL]:

I’m at the [URL="https://www.theguardian.com/world/bahamas"]Bahamas[/URL] National Emergency Management Agency headquarters in Nassau where a delegation of Caribbean leaders just departed for a fly over trip to see the destruction on Abaco Islands.[INDENT] Mia Mottley, prime minister of Barbados is part of the delegation and took a minute to talk to the Guardian about her thoughts on hurricane Dorian’s links to the climate crisis. She did not pull her punches.

‘We are on the front line of the consequences of climate change but we don’t cause it,’ she said.
‘And the vulnerability that attaches therefore to us is a matter we’re trying to get the international community to deal with consistently.’
[/INDENT]Follow the Guardian’s Hurricane Dorian [URL="https://www.theguardian.com/world/live/2019/sep/05/hurricane-dorian-carolinas-latest-live-updates-bahamas-us"]live blog[/URL] for more updates from Laughland in Nassau.

[/QUOTE][/INDENT]

[QUOTE=kladner;525282]Mia Mottley, prime minister of Barbados is part of the delegation and took a minute to talk to the Guardian about her thoughts on hurricane Dorian’s links to the climate crisis. She did not pull her punches.[/QUOTE]

Yeah... Our Prime Minister is a serious woman who speaks her mind!

On Sunday my pile of bargainhardware.co.uk computers stopped responding. Yesterday I noticed that the (rather expensive 10Gbit SFP) switch on top didn't admit to any of its ports being connected; I unplugged the cluster and plugged it in again, and got a loud bang, a bad smell, and tripped the circuit-breaker for the outbuilding and the circuit-breaker for the whole outbuilding on the main distribution board.

And two of the other Linux boxes haven't come back cleanly from the unexpected power cut.

I fear fib(1475) will not be factored as quickly as I was hoping.

[QUOTE=fivemack;526044]On Sunday my pile of bargainhardware.co.uk computers stopped responding. Yesterday I noticed that the (rather expensive 10Gbit SFP) switch on top didn't admit to any of its ports being connected; I unplugged the cluster and plugged it in again, and got a loud bang, a bad smell, and tripped the circuit-breaker for the outbuilding and the circuit-breaker for the whole outbuilding on the main distribution board.

And two of the other Linux boxes haven't come back cleanly from the unexpected power cut.

I fear fib(1475) will not be factored as quickly as I was hoping.[/QUOTE]
Oh dear.

My recent experience is nowhere near as bad as yours. On returning home I upgraded all the UK kit's operating systems. Tedious but ultimately successful. However, the 4TB disk which holds all the household system's backups is dying. Many difficult-to-read blocks and 188 bad ones. Took 48 hours just for the bad block scan. The filesystem appoears to have minor damage and it's already taken 18 hours to run; $DEITY knows when it will finish.

Just ordered three 2GB disks which will be put into a RAID-5 array under zfs. I'm just hoping I can get around 1.1TB off the old disk and onto the new.

[QUOTE=xilman;526048]Oh dear.

My recent experience is nowhere near as bad as yours. On returning home I upgraded all the UK kit's operating systems. Tedious but ultimately successful. However, the 4TB disk which holds all the household system's backups is dying. Many difficult-to-read blocks and 188 bad ones. Took 48 hours just for the bad block scan. The filesystem appoears to have minor damage and it's already taken 18 hours to run; $DEITY knows when it will finish.

Just ordered three 2GB disks which will be put into a RAID-5 array under zfs. I'm just hoping I can get around 1.1TB off the old disk and onto the new.[/QUOTE]But where are your backups? You [i]do[/i] have backups, right?

[size=1]RAID ain't a backup solution either.[/size]

[QUOTE=xilman;526048]Oh dear.

My recent experience is nowhere near as bad as yours. On returning home I upgraded all the UK kit's operating systems. Tedious but ultimately successful. However, the 4TB disk which holds all the household system's backups is dying. Many difficult-to-read blocks and 188 bad ones. Took 48 hours just for the bad block scan. The filesystem appoears to have minor damage and it's already taken 18 hours to run; $DEITY knows when it will finish.

Just ordered three 2GB disks which will be put into a RAID-5 array under zfs. I'm just hoping I can get around 1.1TB off the old disk and onto the new.[/QUOTE]That was a surprise: under 15 minutes longer to wait.

[QUOTE=retina;526049]But where are your backups? You [i]do[/i] have backups, right?

[size=1]RAID ain't a backup solution either.[/size][/QUOTE]This disk holds the backups for all the other systems. The originals are still in place, AFAIK.

Please don't try to teach me how to suck eggs. I've been taking backups in a professional capacity for over thirty years. How many other people here can read data taken in 1982 and copied from 8" CP/M format floppies all the way through to the current 4TB WD-Red drive? Essentially every email I've sent and received in the last 25 years is still available on live storage. The exceptions are spam and some contents of some publicly available mailing lists. When one of my systems is retired its disk is generally kept for a few years in case I need to use it as a backup. Yes, I do still have 8" floppy drives and a bunch of their disks. I've no idea whether they are still usable without having to go to inordinate trouble.

I've been using RAID systems for about 25 years. That is within 5 years or so of the term being defined. I am well aware that RAID is not in itself a backup solution; it can be a valuable but inessential part of a backup solution. The point of my plan to use RAID for the backup storage is resilience against failure of any one disk in the set which is used to hold the backups.

A backup system has to have a termination condition for the recursion implied by a perceived need to have a backup to use in case a higher-level backup fails. My risk analysis and cost-benefit analysis indicates that a single-level master back-up scheme is appropriate. Within that master are monthly snapshots of each of the component file systems which have been backed up. These snapshots are not backups either; they are archives. Until I run out of disk space, which is essentially never because doubling available storage is a manageable expense, those snapshots are kept "forever".

When the disks have been installed and populated the old 4TB disk will be put into storage for a year or two before being scrapped or reformatted and used for scratch storage of unimportant data. such as images of CDs and DVDs which are difficult to mount in bulk and generally not very fast to access.

[QUOTE=xilman;526048]Took 48 hours just for the bad block scan. The filesystem appoears to have minor damage and it's already taken 18 hours to run; $DEITY knows when it will finish.

Just ordered three 2GB disks which will be put into a RAID-5 array under zfs. I'm just hoping I can get around 1.1TB off the old disk and onto the new.[/QUOTE]

Please forgive me if I'm telling you how to chew gum, but...

Personally, [URL="https://www.gnu.org/software/ddrescue/"]ddrescue[/URL] has saved my butt *many* times. Also, I prefer RAID-6 over RAID-5. Nice to have the array fully utilized, rather than simply "hot spare(s)".

[QUOTE=chalsall;526058]Please forgive me if I'm telling you how to chew gum, but...

Personally, [URL="https://www.gnu.org/software/ddrescue/"]ddrescue[/URL] has saved my butt *many* times. Also, I prefer RAID-6 over RAID-5. Nice to have the array fully utilized, rather than simply "hot spare(s)".[/QUOTE]There is a trade-off.

Having two parity disks in a classic RAID array impacts write performance over having only one. There is an argument that if you have a "spare" disk it should be kept cold because spinning it takes power, leading to extra thermal load on the enclosure, and mechanical wear (or electrical wear if it's a SSD).

Having two parity disks means that you need to purchase an extra disk. Whether it is better to use it for data storage or for parity is another risk-assessment and cost-benefit exercise. If the likelihood of a further disk failure during a RAID-5 rebuild is unacceptably high, don't use RAID-5. I estimate that the risk is sufficiently low for my purposes so I can start with three disks.

Sloppy nomenclature alert: I've been using the term "RAID-5" when I really mean "RAID-Z1". The Wikipedia article for [URL="https://en.wikipedia.org/wiki/ZFS#RAID_(%22RaidZ%22)"]zfs[/URL] has a good description of how it all works and, in particular, how RAID-Z1 circumvents some of the shortcomings inherent in RAID-5.

Anyway, if I had four disks I'd use a pair of mirror vdevs.

Thank you for reminding me about ddrescue.