Posts: 2
Joined: Wed Jun 08, 2016 6:07 pm

I/O performance question(s)

Fri Oct 12, 2018 3:28 pm

Hey everyone,

after having spent some time with Jehanne and Harvey running over Windows 10 (and I am really impressed), I have made the decision that I want to use "a Plan 9" as a backup server for my various web projects (and possibly my code repositories and my nextCloud, just in case).

A full backup of all of them would sum up to quite a couple of gigabytes, so I'd probably perform incremental backups every day or so - there rarely are enough changes to make those large - with a full backup every month. Now I "only" have to decide about whether to use a (cluster of) RPi(s) with 9Pi or to rent another server and wait for a self-hosting version of Harvey or Jehanne.

So what I want to know is:
- How well does 9Pi perform when downloading and writing large amounts of data to an attached HDD (or even two of them)?
- Would you suggest me to just don't do that and why? (Or encourage me. Please encourage me.)

Bakul Shah
Posts: 322
Joined: Sun Sep 25, 2011 1:25 am

Re: I/O performance question(s)

Sat Oct 13, 2018 1:13 am

You can use venti for backups -- it is a content addressable block storage. It is not the fastest but may be good enough if your incrementals are on the order of few hundred megabytes. You never do *full backup* every month as each unique block is written only once. The end result of each backup is a single hash value or fingerprint, that of the root block. Incremental backups are faster if the venti client is given the fingerpoint of a previous backup as it avoids sending a block to the venti server if it is already on the backup.

A full restore may be slow however. One limit is that a 'Pi is a USB2 device.

If you are backing up a unix system, you can use relevant tools from plan9port such as vac.

Posts: 2
Joined: Wed Jun 08, 2016 6:07 pm

Re: I/O performance question(s)

Sat Oct 13, 2018 1:29 am

The servers run illumos and FreeBSD, I guess that counts as "UNIX". :)

I hope I won't ever need a backup, so I'm fine with relatively slow restoring, assuming that I won't have to restore all servers on the same day... :D my major problem was my fear that fetching today's backups might be a slow task. But wouldn't downloading and writing be even slower?

I had not thought of venti en detail - so I could just log into my servers remotely, dump my databases and venti all changed blocks? Ah, too easy. :oops: About the relative size: One of the servers I want to "save" is exclusively dedicated to WordPress. A complete WordPress backup is an 1.5 GB .txz file - with minor changes every few days, never more than just one new picture or something. So my decision seems to boil down to the size of daily changes...

How many HDDs does 9Pi support?

Posts: 14
Joined: Mon Apr 29, 2013 11:57 am

Re: I/O performance question(s)

Mon Apr 27, 2020 7:10 pm

Would WormDrive fs, if it knew flash block rewrite size. Save wear on the SDcard
new file versions to memory blocksize, linux can r/o /boot, then overlay or RAID writes.

At least 9fs got the overlay out there. User space FUSE.
Pi 3B+ - Ham, Tech Net, Linux / Mac / PC, Programmer (for IF author).

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