cokernel_hacker

11 ms·

151.
by cokernel_hacker 14y ago
The most common implementation technique that I know of is to include a small constant number (~4) bytes of the actual name next to the hash.
152.
by cokernel_hacker 14y ago
Variable length keys are difficult to implement efficiently. The alternative is not doing file name lookups by key query which would damage performance in unpatholgical cases.
153.
by cokernel_hacker 14y ago
Sadly, this article gets some stuff about btrfs wrong. Allow me to clarify: * First off, btrfs does not use "hash tables". Instead, it uses hashes to create keys that index into B-Trees. The problem is that hash collisions are not handled w
154.
by cokernel_hacker 14y ago
As a professional storage engineer, your comment strikes my heart with horror. A reproducible bug that causes a crash/hang/loss of data in your file system in patently unacceptable. We labor to design a system that stores data safely to a s
155.
by cokernel_hacker 14y ago
I like write-anywhere/COW filesystems. Unfortunately the open source ones kinda blow due to interesting performance penalties (I'm looking at you, btrfs back ref management) or crazy memory usage/non-extent based systems/read-modify-write i
156.
by cokernel_hacker 14y ago
My apologies but what sciurus might be addressing and what I am talking about are addressing two very different things. There is a bug in ext4, https://lkml.org/lkml/2012/10/25/521 Note that this is dated after the "Wed, 24 Oct 2012 17:
157.
by cokernel_hacker 14y ago
I would rather not have byzantine relations between fragments of code make up the policy of my file system's metadata resiliency thank-you-very-much. I would rather prefer that stale journal replays be no-ops, even at the expense of making
158.
by cokernel_hacker 14y ago
This is symptomatic with one of my two big problems with journalling oriented file-systems. My problems with journalling are two fold: 1) They are very slow: 1a) You have a nice big sequential write into the journal, which is OK. 1b) A flus
159.
by cokernel_hacker 14y ago
The good ideas taken from plan9 aren't isolated to it and could have been fostered outside of it, perhaps speeding up adoption of those ideas.
160.
by cokernel_hacker 14y ago
> That's a strange way to describe research and experimentation (though not strictly incorrect). Many of the modern OS research papers that I have read take an existing solution and mess with it. As an example, many file system papers t
161.
by cokernel_hacker 14y ago
My general take from observing their culture is dogmatic vs pragmatic. plan9 and go are dogmatic, they exist because the status quo is bad and something must be done . This is not to say their ideas are bad! Some of them are great but ma
162.
by cokernel_hacker 14y ago
And "just" a 32x increase in flash size.
163.
by cokernel_hacker 14y ago
Mini-filters are FS level as are VFS solutions. How do you tell a thing that sits at the VFS level about multiple devices? You could probably do it, nothing storage engineers solve is unsolvable :) It certainly seems unnatural. Most of thos
164.
by cokernel_hacker 14y ago
StorSimple, 3PAR, etc. all appear to be appliances. What I am trying to get as is subtle so I will try to be a little bit more explicit. StorSimple can dominate the appliance it is made out of to provide its services. Fusion Drive cannot do
165.
by cokernel_hacker 14y ago
Tiered storage has been done before, this is true. However, they are dedicated systems. If "Fusion Drive" is at the OS level, that means it shares resources with the rest of the system which presents more/different challenges.
166.
by cokernel_hacker 14y ago
Not even sorta similar, "ReadyBoost" is a cache "Fusion Drive" provides the union of space. They are in the same vein of "hide the slowness of rotational media" but that is a pretty huge vein.
167.
by cokernel_hacker 14y ago
This is not a hybrid drive, it is two drives as evidenced by the picture of the iMac that Phil Schiller showed. This is more akin to "tiered storage" which has existed before, just not in the consumer space which prevents more/different cha
168.
by cokernel_hacker 14y ago
You are comparing "Momentus" a hybrid drive with "Fusion Drive" a tiered storage solution . Fusion Drive gives you a giant, huge SSD drive compared to Momentus' on-drive flash. We are talking about orders of magnitude in difference in fl
169.
by cokernel_hacker 14y ago
You are not correct, it is _not_ a cache but instead something that provides the union of storage between two drives. Remember, the examples have stuff _only_ on the SSD. Instead, this appears to be an implementation of so-called "tiered st
170.
by cokernel_hacker 14y ago
vector::emplace_back ameliorates by allowing new elements to be constructed in-place [1] [1] http://en.cppreference.com/w/cpp/container/vector/emplace_ba...
171.
by cokernel_hacker 14y ago
Transactional filesystems have been implemented at considerable expense. To be clear, I mention transactions at a high enough level to encompass deleting a subdirectory (most reasonably implemented filesystems have support for tiny transact
172.
by cokernel_hacker 14y ago
YAFFS is a log-structured filesystem, just like F2FS. Log-structuring gives you a data organization protocol. This protocol gives you an implicit crash-recovery story, there is no need for additional journaling on top of it. Journalling is
173.
by cokernel_hacker 14y ago
They are all cryptographers and at least three of them have deep academic backgrounds... Guido Bertoni: http://www.informatik.uni-trier.de/~ley/db/indices/a-tree/b/... Joan Daemen: http://www.informatik.uni-trier.de/~ley/db/indices/a-tre
174.
by cokernel_hacker 14y ago
Clang is a C/C++ compiler, it has nothing to do with linking! The lld [1] project aims to be a linker, it is still relatively young. [1] http://lld.llvm.org/
175.
by cokernel_hacker 14y ago
My competing definition includes safety and performance. Not about how the system works a single epsilon after an operation but perhaps reading data that we wrote last month, or last year and doing it using the hardware's resources efficien
176.
by cokernel_hacker 14y ago
I am afraid that is not even close to accurate. If you define "95% of problems" to be "reading and writing data such that data is read and written" sure, great. However, there are two little, minor things that file systems care about: perfo