Gentoo Archives: gentoo-user

From: Mick <michaelkintzios@×××××.com>
To: gentoo-user@l.g.o
Subject: Re: [gentoo-user] Safeguarding strategies against SSD data loss
Date: Mon, 27 Oct 2014 15:22:42
Message-Id: 201410271522.32452.michaelkintzios@gmail.com
In Reply to: Re: [gentoo-user] Safeguarding strategies against SSD data loss by Rich Freeman
1 On Monday 27 Oct 2014 13:13:00 Rich Freeman wrote:
2 > On Mon, Oct 27, 2014 at 7:11 AM, Alan McKinnon <alan.mckinnon@×××××.com>
3 wrote:
4 > > On 27/10/2014 11:24, Mick wrote:
5 > >> I'm starting a new thread so as to not hijack the one about alternative
6 > >> kernels, but continue with something Volker raised.
7 > >>
8 > >> On Sunday 26 Oct 2014 23:25:50 Volker Armin Hemmann wrote:
9 > >>> as others have written already: ssd.
10 > >>>
11 > >>> With a caveat: if an ssd dies, it will die suddenly. Without a warning.
12 > >>> Usually 5 minutes before the start of your weekly or monthly backup
13 > >>> run. And that is first hand experience.
14 > >>
15 > >> I haven't yet started using SSD and have wondered what sort of a system
16 > >> should I set up to guard against such instantaneous catastrophic
17 > >> failures. I am interested to hear what strategies people deploy to
18 > >> avoid data loss with SSDs, especially on laptops that don't have the
19 > >> luxury of raid redundancy.
20 > >>
21 > >> With spinning drives I use tar and rsync at regular intervals. There
22 > >> have been a few rare cases where a drive failed without prior notice -
23 > >> the last one after a reboot. In such cases I am prepared to live with
24 > >> the risk of some data loss, on machines where raid is not an option.
25 > >
26 > > Without some form of redundancy that would be your best strategy -
27 > > decent and frequent backups
28 >
29 > It isn't the most mature solution, but btrfs send has a lot of
30 > potential here. One of the main costs of backups is the need to walk
31 > all the data that you intend to backup to find changes. Rsync can do
32 > wonders with minimizing bandwidth, and something like duplicity which
33 > uses librsync can do wonders to minimize the size of serializing that
34 > in files, but both require reading the entire filesystem.
35 >
36 > Btrfs send can serialize a set of changes in the filesystem by reading
37 > only the btree nodes and extents that have changed. It is fairly
38 > close to a git pull in that sense, though git doesn't use balanced
39 > trees. That would greatly reduce the IO cost of frequent backups.
40 > You would just periodically create a new snapshot, do a send between
41 > the last snapshot and the new one, and once you've confirmed
42 > successful completion of that you'd delete the old snapshot.
43 >
44 > Of course, IO seeks aren't nearly as expensive on an SSD as they are
45 > on a hard drive. I haven't really done a lot of rsync on ssds while
46 > using them so I can't really vouch for how much the IO impacts
47 > operations.
48 >
49 > But yes, backup and RAID are really your only options for SSD failure
50 > as far as I can see it. That and limiting the amount of data that
51 > can't be re-generated. If you just save the world file and all of
52 > /etc you could probably rebuild a Gentoo install fairly quickly on a
53 > new drive, and then you're just left with /home and whatever else you
54 > happen to have installed that sticks stuff in /var that you care
55 > about.
56
57
58 Thanks Rich, I have been reading your posts about btrfs with interest, but
59 have not yet used it on my systems. Is btrfs agreeable with SSDs, or should I
60 be using f2fs:
61
62 http://www.phoronix.com/scan.php?page=article&item=linux_314_ssdfs&num=1
63
64 --
65 Regards,
66 Mick

Attachments

File name MIME type
signature.asc application/pgp-signature

Replies

Subject Author
Re: [gentoo-user] Safeguarding strategies against SSD data loss Rich Freeman <rich0@g.o>
Re: [gentoo-user] Safeguarding strategies against SSD data loss Volker Armin Hemmann <volkerarmin@××××××××××.com>