[ale] backup/restore mail from USB external drive

Thu Feb 13 14:46:06 EST 2014

If performance is your main driver why in God’s name are you using NAS vs SAN anyway?

Jeffrey C. Lightner
Sr. UNIX Administrator

DS Waters of America, Inc.
5660 New Northside Drive NW
Suite 250
Atlanta, GA  30328

P: 678-486-3516
C: 678-772-0018
F: 678-460-3603
E: jlightner at water.com

From: ale-bounces at ale.org [mailto:ale-bounces at ale.org] On Behalf Of Jeff Hubbs
Sent: Thursday, February 13, 2014 1:18 PM
To: ale at ale.org
Subject: Re: [ale] backup/restore mail from USB external drive

Because the probability of having an unrecoverable read error on RAID5 rebuild starts to come up off the peg and RAID6 isn't much better.

Since they came on the market, I've found that NASses both cheap (e.g., LaCie) and expensive (IBM-rebadged NetApp where you paid extra by the protocol) aren't worth spit.  Sure, they work (sort of - I got a LaCie guy to admit to me once that their NFS implementation was badly broken but they didn't really care), but the sorts of things you may expect to do administratively, like make fast copies internally, scan for viruses, or search for files (for instance, because someone had an errant mouse drag that moved their quarterly report spreadsheets to God-knows-where) are ruinously slow.  To give you some idea, I once replaced said rebadged NetApp - that cost about $40,000 - with a SuperMicro-based Gentoo Linux file server with a mix of SAS and SATA drives in 24 slots in the front, two SSDs inside, two SAS controllers (with RAID10 with the RAID1 pairs split across controllers so a controller would die and you still wouldn't lose the volume), and two four-core CPUs.  All that plus a warm-swap machine, spare mobo, spare CPUs, power supplies, NICs, disk controllers, and RAM (to heck with waiting for some schmoe from e.g. IBM's field service contractor to find your site and replace parts in a machine he might have never seen before anyway) cost about $25K, and it could scan its main shared-space volume with clamav at over 200MiB/s.  In-slot NICs were bonded for I/O (the on-mobo NICs were not used in order to reduce the risk to the mobo).  It was NFSv3-ready, had Samba of course, and daemons for anonymous chrooted FTP and rsync - and there was talk at one time of having it serve out CVS (it'd might as well!).

So when you talk to me about what RAID configuration I'd recommend for 12x2TB drives in a NAS, I'm thinking of the operational risks you've baked into your IT resources just by having a NAS in the first place and wondering whether or not RAID nuances would matter all that much at the end of the day.  Ask yourself this:  even if it were just half full, how long would it take you to do a complete read for backup-making purposes?  See, in this day and age, it's real easy to have giant amounts of storage and therefore giant amounts of stuff being stored, all connected to everything else by what are very tiny pipes, relatively speaking.

On 2/12/14, 6:43 PM, Ray Vastly wrote:

Why should you avoid raid 5 or 6 when using large hard disks? What Raid configuration would you recommend for 12 HDDs each 2 TB in a NAS?
On Feb 12, 2014 6:40 PM, "Jeff Hubbs" <jhubbslist at att.net<mailto:jhubbslist at att.net>> wrote:
On 2/12/14, 5:00 PM, Lightner, Jeff wrote:
<snip>

You really should be using RAID6 or RAID10 rather than RAID5 as it is even more redundant (i.e. can survive 2 disks failures).
And you shouldn't be using RAID5 or RAID6 at all if your drives are 750-1000GB or larger.

Mail and database servers would be two good places to make use of snapshotting filesystems.  Note that some email systems that use message stores go insane if the message store is not in the state that the rest of the email system presumes it's in, so you have to make sure that your backup/recovery scheme doesn't capture messages and message metadata/index in different states.

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