LWN: Comments on "Red Hat Enterprise Linux 7.4 released"

OpenLDAP server deprecated?

dpal — Mon, 28 Aug 2017 20:43:05 +0000

Hello,

Let me clarify last comment a bit.
Red Hat does not offer 389-ds as a supported option. The bits are there in RHEL and used and supported in context of IdM or Red Hat Directory Server product but not if installed by themselves.
If you need a solution that serves your identity management needs - IdM is the one. It is included with RHEL subscription without extra cost. If you need a directory server as a back end for your applications Red Hat Directory Server is the way to go. It is a separate product with a price tag. If you need a simple LDAP server for development or testing in many cases IdM can fit the bill. If you want an LDAP server for back end for an application and plan to use it in production you probably want a dedicated dev/test RHDS environment anyways. If you want something to play with you can use 389-ds package on RHEL which will not be supported but will work or you can use CentOS in this case. In general there is plenty of options for every taste. If some use case is missing or some of the assumptions about the use of LDAP server functionality is wrong, Red Hat will be grad to hear your feedback, just open a support case or post a comment here.

Thank you,
Dmitri

Btrfs has been deprecated?

anton — Mon, 21 Aug 2017 17:05:25 +0000

We recently played around with Btrfs and RAID1, and what we saw looked somewhat rough (it's relatively easy to get the filesystem into an unrecoverable read-only state; then you have to copy the data over), but we did not experience data loss. You can read about our experience here.

Btrfs has been deprecated?

Wol — Sun, 13 Aug 2017 14:47:38 +0000

And, not being a storage device, MD does not see this as its responsibility.

Yes, it might be a nice addition, but it's added complexity, and it would need somebody to step up to the plate and implement it (plus it would require mucking about with the layout - there may or may not be somewhere to store the fact that stripes are empty or in use).

Cheers,
Wol

Btrfs has been deprecated?

matthias — Wed, 09 Aug 2017 07:45:47 +0000

This would work for large TRIM requests. However, TRIM requests are at block granularity. To properly track, which stripes have valid data, MD would need to store for each block whether it has valid data. Otherwise, it cannot tell whether some TRIM request has removed the last used block from a stripe.

Btrfs has been deprecated?

meuh — Tue, 08 Aug 2017 15:39:32 +0000

FS -> (DM ->) MD -> HDD

If FS initiate TRIM request (discard), beside forwarding the request to HDD, MD can record that one or more stripe are not storing useful information any more (such flag would be invalided by a write on the stripe). Going to the status of each stripes during recover, MD can process only the useful part of the RAID array.

Btrfs has been deprecated?

jhhaller — Thu, 03 Aug 2017 19:11:12 +0000

As a different guess, Ceph is evolving to no longer require an underlying filesystem, and Red Hat would rather support Ceph.

But, having put together a BTRFS RAID 5, I wouldn't recommend it, even if the data loss problems get fixed. Scrubbing a large RAID 5 filesystem is interminably slow. BTRFS is happy to let all writes go to RAM until a flush is requested. At that point, the system comes to a grinding halt while all that data is written out to the drives.

Btrfs has been deprecated?

Wol — Thu, 03 Aug 2017 08:30:57 +0000

Sorry, I don't get it.

md-raid works at the partition level. It knows nothing, cares nothing, about the file system above it so even if you sent a discard to md it wouldn't have a clue what to do with it.

Cheers,
Wol

Btrfs has been deprecated?

Wol — Thu, 03 Aug 2017 08:29:17 +0000

So how on earth does ZFS get around that issue? And anyway, no a mdraid does not necessarily cause that problem at all! Yes I would certainly advise against using raid-5 for a large (5 or more) disks array, because losing a disk puts the array in a state of no redundancy.

But firstly if the failed disk is even partially recoverable, that will massively reduce the stress on the array. (As always, we need developers - getting that to work seamlessly is on the hit list of jobs needing doing :-(

Secondly, if you've been scrubbing the array like you're supposed to, you know very well that the array is good and will have no trouble coping with a rebuild.

And thirdly, how on earth is ZFS supposed to know what is on the failed disk, other than by doing a scan of the rest of the disks, stressing them in exactly the same way as md-raid!?

(And yes, md-raid does scan the entire underlying partition like you suggest, but there are easy - if controversial - ways round that.)

Cheers,
Wol

Btrfs has been deprecated?

joib — Thu, 03 Aug 2017 04:14:20 +0000

> I think is related to acquisition of Permabits by Redhat.

phoronix (yes, sigh), reports that RH is developing stratis, which is some kind of management daemon + API/CLI tying together LVM + XFS. Perhaps the Permabit stuff too one day. http://phoronix.com/scan.php?page=news_item&px=Strati...

OpenLDAP server deprecated?

evad — Thu, 03 Aug 2017 00:02:12 +0000

Its been 'deprecated' or at least discouraged for many years in RHEL (since v5 IIRC). They prefer customers to use 389-ds instead, or Red Hat Directory Server.

Btrfs has been deprecated?

quotemstr — Wed, 02 Aug 2017 23:37:54 +0000

Discard ought to be provide exactly the right information to md, right?

OpenLDAP server deprecated?

kbrantley — Wed, 02 Aug 2017 21:51:58 +0000

Anyone have any insights as to why the OpenLDAP server has been depreciated?

On the authentication front I get it; they're really pushing IdM and rightfully so (anonymous LDAP access isn't enough these days, and IdM does all of the security for you out of the gate). But, there are a lot more uses of OpenLDAP than just identity management...

Btrfs has been deprecated?

wx — Wed, 02 Aug 2017 21:25:32 +0000

> If you want RAID6, use md/raid6 (or "hardware RAID") underneath btrfs.

No, don't do that.

In an md raid, a disk failure will cause the contents of the _entire_ disk to be resynced as md does not differentiate between used and unused disk space - only the filesystem one layer up has that info. With today's disks a resync takes ages and puts a lot of stress on the other disks in the array significantly increasing the risk of additional drive failures in the worst possible situation: in an already degraded state.

Customers who understand and care about these issues are already using ZFS (not necessarily under Linux) and have no reason to switch. At the end of the day there's just no business case for Red Hat in btrfs besides catering to customers who absolutely insist on using Linux but are afraid of legal trouble wrt the CDDL (which Canonical decided would not happen a while back and which hasn't happened to Canonical yet, at least not on public record).

Btrfs has been deprecated?

nix — Wed, 02 Aug 2017 20:53:49 +0000

reflinking via CoW's been working well for a while now, since 4.9 or thereabouts.

Btrfs has been deprecated?

cesarb — Wed, 02 Aug 2017 12:55:35 +0000

> Does anybody know the reasons for this decision?

A comment at HN explains the probable reason: https://news.ycombinator.com/item?id=14909843

Red Hat Enterprise Linux 7.4 released

evad — Wed, 02 Aug 2017 10:12:07 +0000

Not just Chrome - all the 'top' web browsers except Safari require ALPN now.

Btrfs has been deprecated?

danieldk — Wed, 02 Aug 2017 09:50:20 +0000

And AFAIK they are adding support for CoW:

https://lkml.org/lkml/2016/10/12/176

Btrfs has been deprecated?

richard77 — Wed, 02 Aug 2017 06:53:06 +0000

I think is related to acquisition of Permabits by Redhat.
https://www.redhat.com/it/about/press-releases/red-hat-ac...

Red Hat Enterprise Linux 7.4 released

imgx64 — Wed, 02 Aug 2017 06:01:41 +0000

OpenSSL has been updated to 1.0.2k from 1.0.1. This means that serving HTTP/2 will finally work again with Chrome! (it used to work until Chrome 51 where they removed support for NPN, and instead required ALPN for HTTP/2. ALPN was added in OpenSSL 1.0.2).

Btrfs has been deprecated?

smckay — Wed, 02 Aug 2017 02:18:45 +0000

How many btrfs devs does Red Hat employ? How many xfs devs? How many Red Hat customers are using xfs vs. btrfs, and what customer delta would they get from promoting btrfs to supported? In short, what's the cost/benefit on including btrfs in the set of configurations they support?

I know the answer to exactly zero of these questions but I suspect their answers are relevant to RH's decision to dump btrfs.

Btrfs has been deprecated?

neilbrown — Tue, 01 Aug 2017 23:15:02 +0000

> I'd guess it's due to Btrfs' RAID being unfinished and dangerous for several years:

That may be a good reason to disable btrfs RAID support. It doesn't seem like a good reason to dump btrfs altogether. If you want RAID6, use md/raid6 (or "hardware RAID") underneath btrfs.

Btrfs has been deprecated?

flussence — Tue, 01 Aug 2017 22:51:43 +0000

More specifically, I'd guess it's due to Btrfs' RAID being unfinished and dangerous for several years: https://btrfs.wiki.kernel.org/index.php/Status

It's an okay FS on my desktop, and I guess it works for Facebook where they can afford to do RAID6 at the building level, but this sucks hard for anyone wanting to use it on a normal-sized server.

Btrfs has been deprecated?

Paf — Tue, 01 Aug 2017 20:01:10 +0000

More than that, XFS is currently the default option for the root filesystem and the other created-by-default file systems/partitions.

Btrfs has been deprecated?

jhoblitt — Tue, 01 Aug 2017 19:54:32 +0000

In the interim xfs has become a first class citizen, moving from a rhel add-on to supported in the base distro. I presume xfs has quite a large installation base (I have certainly used it heavily in the past for large filesystems) among rhel customers. It might be as simple as limiting the number of supported filesystems.

Btrfs has been deprecated?

dany — Tue, 01 Aug 2017 19:43:12 +0000

From experience (btrfs+directIO), I bet on data loss/corruption scenarios. Can be something else of course.

Btrfs has been deprecated?

ubhofmann — Tue, 01 Aug 2017 18:55:23 +0000

I'm surprised by the paragraph below:

"The Btrfs file system has been in Technology Preview state since the initial release of Red Hat Enterprise Linux 6. Red Hat will not be moving Btrfs to a fully supported feature and it will be removed in a future major release of Red Hat Enterprise Linux."

Does anybody know the reasons for this decision?