Mark,
Questions, and some comments.
Questions:
What have you done to tune your zfs?
Do you use a ZIL? and or an L2ARC?
How much ram do you have?
What compression level are you using on zfs?
I reflexively put a ZIL on my system but I'm curious if anyone has
experimented with BackupPC performance on zfs with and without the ZIL.
Comments:
I built a backuppc on zfs system at my last job, but I took the opposite
approach on compression. I disabled compression and dedupe on zfs and
let BackupPC handle those jobs. I haven't seen load problems, but I do
notice that the tranfer speed reported by backuppc varies a lot between
different windows clients. Anywhere from 1.4 MB/s to 41 MB/s. This is
partly due to network speed since some machines are on Gb connections,
but most are on 100Mb. There also seems to be some dependence on the age
and condition of the windows boxes.
BackupPC reports 76486 Gb of fulls and 1442 Gb of incrementals.
zfs list shows 11.9 Tb allocated from the 65Tb pool for backuppc data.
Which gives me about a 6.4 fold reduction in storage, slightly less than
the roughly 7.5 fold reduction that you see. My data comes from user
files on 12 windows 7 machines.
This is a poor comparison since we have different data sets, but it
would appear that BackupPC's internal dedupe and compression is
comparable to, or only slightly worse than what zfs achieves. This in
spite of the expectation that zfs block level dedupe might find more
duplication than BackupPC's file level dedupe.
Russ Poyner
On 12/17/13 07:50, Mark Campbell wrote:20
> I too am using ZFS, and I can honestly say that ZFS works great, up to a
> point. rsync does seem to take up an inordinate amount of resources, but in
> a smaller shop like mine, it's been tolerable. I think it would work in a
> larger shop too, but the system resource requirements (CPU/RAM) would grow
> larger than what you would expect normally. I've had a couple of instances
> of performance issues in my setup, where over time, rsync was uploading data
> to the system faster than zfs could process it, and so I'd watch my load go
> through the roof (8.00+ on a quad core system), and I would have to stop
> BackupPC for an hour or so, so that ZFS could catch up, but other than that,
> this system has actually handled it fairly well.
>
> What I really like about ZFS though, is the deduplication coupled with
> compression. I've disabled compression in BackupPC to allow ZFS to properly
> do the dedup & compression (enabling compression in BackupPC kills ZFS' dedup
> ability, since it messes with the checksums of the files), and I'm getting
> numbers in the range of 4.xx deduplication. My ZFS array is 1.12TB in size,
> yet, according to BackupPC, I've got 1800GB in fulls, and 2400GB in
> incrementals. When I query the array for actual disk usage, it says I'm
> using 557GB of space... Now that's just too cool.
>
> Thanks,
>
> --Mark
>
>
> -----Original Message-----
> From: Tim Connors [mailto:tconnors AT rather.puzzling DOT org]
> Sent: Monday, December 16, 2013 10:00 PM
> To: General list for user discussion, questions and support
> Subject: Re: [BackupPC-users] What file system do you use?
>
> On Mon, 16 Dec 2013, Timothy J Massey wrote:
>
>> One last thing: everyone who uses ZFS raves about it. But seeing as
>> (on
>> Linux) you're limited to either FUSE or out-of-tree kernel modules (of
>> questionable legality: ZFS' CDDL license is *not* GPL compatible),
>> it's not my first choice for a backup server, either.
> I am using it, and it sucks for a backuppc load (in fact, from the mailing
> list, it is currently (and has been for a couple of years) terrible on an
> rsync style workload - any metadata heavy workload will eventually crash the
> machine after a couple of weeks uptime. Some patches are being tested right
> now out of tree that look promising, but I won't be testing them myself until
> it hits master 0.6.3.
>
> Problem for me is that it takes about a month to migrate to a new filesystem.
> I migrated to zfs a couple of years ago with insufficient testing. I should
> have kept on ext4+mdadm (XFS was terrible too - no faster than ext4, and
> given that I've always lost data on various systems with it because it's such
> a flaky filesystem, I wasn't gaining anything).
> mdadm is more flexible than ZFS, although harder to configure. With
> mdadm+ext4, you can choose any disk arrangement you like without being
> limited to simple RAID-Z(n) arrangements of equal sized disks. That said, I
> do prefer ZFS's scrubbing compared to mdadm's, but only slightly. If I was
> starting from scratch and didn't have 4-5 years of backup archives, I'd tell
> backuppc to turn off compression and munging of the pool, and let ZFS do it.
>
> I used JFS 10 years ago, and "niche buggy product" would be my description
> for it. Basically, go with the well tested popular FSs, because they're not
> as bad as everyone makes them out to be.
>
> --
> Tim Connors
>
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