Re: Re (2): Archiving on optical media
peter@easthope.ca writes:
> From: rhkramer@gmail.com
> Date: Mon, 28 Feb 2022 09:52:35 -0500
> > What has been your experience with reliability of SD cards for backup?
>
> My explanation was ambiguous. =8~| The primary medium here is SD.
> The backup is optical.
>
> The oldest SD card I have was purchased about 2012. The label was
> NextTech. Purchased via eBay from a seller in Ontario or Quebec. It's
> been reformatted 2 or 3 times over the years and still works. =8~)
> Recently parts of some files disappeared or showed garbled
> information. The card has served better than I expected. Probably due
> for retirement. =8~)
>
> Since 2012 I've purchased three Kingston 8 GB SDs. Two are used in
> mobile phones; one is system store in a OLPC XO 1.5. Those SDs
> continue to work with no apparent difficulties.
>
> General policy. Buy only name brands: Kingston, SanDisk, Lexar & etc.
> Buy only from local businesses maintaining a reputation in the
> marketplace. Noname cards only waste time and money.
>
Also, make sure the SD manufacturing technology has wear
leveling. Many cheap SDs do NOT. (They are manufactured in out dated
facilities.)
If used for backups, write the file, then write the check sum of the
file, (perhaps using something linke md5sum(1),) to the disk, with the
same file name plus an extension, so that md5sum can be used to check
the integrity of the data before installing the backup.
For long term archival data, use a new SD, and write once, (perhaps on
multiple SDs, for file reconstruction; any corrupt file on one SD can
probably be retrieved from another SD.) Store at STP for the plastics.
>
> Regardless of reliability of a specific medium, data preservation
> comes from a good backup system. =8~)
>
John
--
John Conover, conover@panix.com, http://www.johncon.com/
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