ZFS - Building, Testing, and Benchmarking
by Matt Breitbach on October 5, 2010 4:33 PM EST- Posted in
- IT Computing
- Linux
- NAS
- Nexenta
- ZFS
If you are in the IT field, you have no doubt heard a lot of great things about ZFS, the file system originally introduced by Sun in 2004. The ZFS file system has features that make it an exciting part of a solid SAN solution. For example, ZFS can use SSD drives to cache blocks of data. That ZFS feature is called the L2ARC. A ZFS file system is built on top of a storage pool made up of multiple devices. A ZFS file system can be shared through iSCSI, NFS, and CFS/SAMBA.
We need a lot of reliable storage to host low cost websites at No Support Linux Hosting. In the past, we have used Promise iSCSI solutions for SAN based storage. The Promise SAN solutions are reliable, but they tend to run out of disk IO long before they run out of disk space. As a result, we have been intentionally under-utilizing our current SAN boxes. We decided to investigate other storage options this year in an effort to improve the performance of our storage without letting costs get completely out of hand.
We decided to spend some time really getting to know OpenSolaris and ZFS. Our theory was that we could build a custom ZFS based server for roughly the same price as the Promise M610i SAN, and the ZFS based SAN could outperform the M610i at that price point. If our theory proved right, we would use the ZFS boxes in future deployments. We also tested the most popular OpenSolaris based storage solution, Nexenta, on the same hardware. We decided to blog about our findings and progress at ZFSBuild.com, so others could benefit from anything we learned throughout the project.
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Mattbreitbach - Tuesday, October 5, 2010 - link
Indeed you can, which is one of the most exciting parts about using software based storage appliances. Nexenta really excels in this area, offering iSCSI, NFS, SMB, and WebDAV with simple mouse clicks.MGSsancho - Tuesday, October 5, 2010 - link
or a single command!FransUrbo - Wednesday, January 11, 2012 - link
Would be really nice to see how ZoL compares. It's in no way optimized yet (current work is on getting the core functionality stable - which IMHO it is) so it would have no chanse against OpenSolaris or Nexenta, but hopfully it's comparative to the Promise rack.http://zfsonlinux.org/
gfg - Tuesday, October 5, 2010 - link
NAS is extremely cost effective in a data center if a large majority of NFS/CIFS users are more interested in capacity, not performance. NDMP can be very efficent for backups, and the snapshots/multi-protocol aspects of NAS systems are fairly easy to manage. Some of the larger Vendor NAS systems can support 100+TB's per NAS fairly effectively.bhigh - Wednesday, October 6, 2010 - link
Actually, OpenSolaris and Nexenta can act as a SAN device using COMSTAR. You can attach to them with iSCSI, FC, Infiniband, etc. and use any zvols as raw scsi targets.JGabriel - Wednesday, October 6, 2010 - link
Also, "Testing and Benchmarking"?Doesn't that mean the same thing and isn't it redundant? See what I did there?
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Fritzr - Thursday, October 7, 2010 - link
This is similar to the NAS<>SAN argument. They are used in a similar manner, but have very different purposes.Testing. You are checking to see if the item performance meets your need & looking for bugs or other problems including documentation and support.
Benchmarking. You are running a series of test sets to measure the performance. Bugs & poor documentation/support may abort some of the measuring tools, but that simply goes into the report of what the benchmarks measured.
Or in short:
Test==does it work?
Benchmark==What does it score on standard performance measures?
lwatcdr - Friday, October 8, 2010 - link
I am no networking expert so please bear with me.What are the benfits of a SAN over local drivers and or a NAS?
I would expect a NAS to have better performance since it would send less data over the wire than a SAN if they both had the same physical connection.
A local drive/array I would expect to be faster than a SAN since it will not need to go through a network.
Does it all come down to management? I can see the benefit of having your servers boot over the network and having all your drives in one system. If you set up the servers to boot over the network it would be really easy to replace a server.
Am I missing something or are the gains all a matter of management?
JohanAnandtech - Sunday, October 10, 2010 - link
A NAS has most of the time worse performance than a similar SAN since there is a file system layer on the storage side. A SAN only manages block and has thus less layers, and is more efficient.A local drive array is faster, but is less scalable and depending on the setup, it is harder to give a large read/write cache: you are limited by the amount of RAM your cache controller supports. In a software SAN you can use block based caches in the RAM of your storage server.
Management advantages over Local drives are huge: for example you can plug a small ESXi/Linux flash drive which only contains the hypervisor/OS, and then boot everything else from a SAN. That means that chances are good that you never have to touch your server during its lifetime and handle all storage and VM needs centrally. Add to that high availability, flexibility to move VMs from one server to another and so on.
lwatcdr - Monday, October 11, 2010 - link
I but that layer must be executed somewhere I thought that decrease in data sent over the physical wire would make up for the extra software cost on the server side.Besides you would still want a NAS even with a SAN for shared data. I am guessing that you could have a NAS served data from the SAN if you needed shared directories.
I also assume that since most SAN are on a separate storage network that the SAN is mainly used to provide storage to servers and than the servers provide data to clients on the lan.
The rest of it seems very logical to me in a large setup. I am guessing that if you have a really high performance data base server that one might use a DAS instead of SAN or dedicate a SAN server just to the database server.
Thanks I am just trying to educate myself on SANs vs NAS vs DAS.
Since I work at a small software development firm our sever setup is much simpler than the average Data center so I don't get to deal this level of hardware often.
However I am thinking that maybe we should build a SAN and storage network just for our rack.