En tiempos de crisis describimos los puntos clave para diseñar una SAN de bajo coste.
- iSCSI
iSCSI es una alternativa a la clásica SAN de fibra óptica, siendo económica su implementación ya que no requiere de una infraestructura y tecnología adiccional Hardware de costosas HBAs y Switches de Fibra. Con sólo un switch ethernet ( o dos que aporten redundancia de acceso) y con un servidor con tarjetas Ethernet de Gigabit junto con unos discos ya tendrías una SAN. Los initiators y targets iSCSI en muchos sistemas vienen con la distribución, al igual que las soluciones de multicamino (multipath).
Existen otras alternativas a iSCSI también basadas en Ethernet como AoE (ATA over Ethernet) que al eliminar una capa de encapsulación de frames (IP) da mayor rendimiento.
- DISCOS
En la actualidad se diponen discos de buen precio y alta capacidad para una solución de bajo TIER. Un ejemplo podría ser 4 discos SATA de 3Gb/s , capacidad 2 TB, 64 MB de Caché y 7200 rpm con un total aproximado de 500€. Proporcionando aproximadamente unos 6 TB en RAID software con MDADM (solución de servidores Linux de RAID software) , que nos da una media de 111 euros por Tera tolerante a fallo (RAID).
Preguntadle a vuestro proveedor de SAN cuanto saldría una amplación de los TB en fibra … 😉
Aunque no es comparable una cabina de discos en fibra en cuanto a rendimiento debido a sus fenomenales características Hardware (tarjetas de fibra operando en modo target y procesadores dedicados, memoria caché del frontend y backend de los discos, …). Además sus discos tienen un rendimiento mayor, 15.000 rpm frente a los 7200 rpm que tienen los discos SATA, comparativamente pueden duplicar las I/Os y mejoras como gestión de colas o DIF T10. Según la necesidad de las aplicaciones del uso intensivo de disco podría ser adecuada una solución de bajo TIER.
- RAID
La tecnología RAID Hardware dejó de ser hace años exclusiva de entornos enterprise y cualquier placa de PC lleva integrado una controladora de discos SATA con soporte de RAID 0,1,5. Por otro lado los resultados del RAID por software (MDADM, ZFS, …) y los gestores de volúmenes (Logical Volumen Manager – LVM ,Solaris Volumen Manager – SVM ,Veritas Volume Manager – VxVM, ZFS, …) demuestran ser alternativa eficaz que complementan de forma segura y hacen flexible cualquier cambio posterior en el almacenamiento.
- MULTIPATH
Una solución SAN en iSCSI necesitaría de un switch ethernet para conectar los Initiator/s con los Target/s. Un diseño en SAN de fibra típico sería redundar HBAs y Switches de fibra proporcionando multicamino (multipah) al sistema eliminando puntos de fallo, se conseguiría de esta forma prevenir de cualquier fallo Hardware la continuidad de acceso a los discos. Esta tolerancia a fallos también es posible realizarse por analogía en iSCSI, redundando tarjetas y switches ethernet, acompañado de un software multipath propio de la distribución o usando nativamente el multipath iSCSI.
- SAN/NAS
Cualquier sistema UNIX/Linux dispone de soporte para protocolos fibra e iSCSI y combinar con cualquier protocolo de compartición de ficheros como SMB o NFS. Ésto nos permitiría crear un servidor que centraliza el almacenamiento en el CPD redireccionándolo a ethernet sobre protocolos de bloques (iSCSI) o de ficheros (SMB,NFS).
También existen soluciones enterprise con esta funcionalidad basadas en software abierto tales como NexentaStor, OpenFiler o FreeNAS.
- Sistemas de Ficheros con reservas
El acceso de diferentes servidores a los mismos volúmes (típico en clústeres) necesitan tener un control de acceso y reservas de forma que haya coherencia en las modificaciones en el sistema de ficheros. Ésto se puede conseguir eligiendo un sistema de ficheros de tipo disco compartido (Share Disk File System) como GFS (REDHAT) o VMFS (VMWARE).
- Controladoras Activo/Activo Activo/Pasivo
Soluciones software tipo IET en servidores linux sobre las tarjetas ethernet del servidor como Enterprise Target iSCSI proporcionará un comportamiento análogo al típico de las controladoras de cabinas de discos en fibra.
- Soporte
El tema más delicado ya que el soporte SAN va en función de la interoperabilidad entre fabricantes destacando los elementos siguientes:
Sistema Operativo – Multipath – HBA-Drivers – Switch – Almacenamiento – Modos del multipath
Y debido a que el diseño de cada elemento en su totalidad no se ajusta a los mismos estándares se necesita una certificación previa entre diferentes fabricantes.
Esta situación cambia bastante en un entorno iSCSI siendo un protocolo/estandar bien definido con una implementación precisa, que crea un marco de interoperatibidad mucho mayor.
Aún así, hablamos de la infrestructura que contiene los datos de una empresa, y si algo en su CPD debe de tener soporte es este almacén de datos. Por lo que el final de este diseño propuesto puede variar bastante si no se quiere contratar soporte … incluyento por ejemplo soluciones de backup, Alta disponibilidad (HA) con replicación síncrona entre dos cabinas de discos, … todo un tema a desarrollar y cuya implementación en producción es aconsejable que deba superar toda una fase de testeo intensivo y planes robustos de contingencia.
Lo aconsejable es buscar soporte en alguna solución tipo Openfiler, siendo una de las soluciones más flexibles que cumple los puntos propuestod … aunque no olvidar que hay que mirar la interoperabilidad con lupa y como ejemplo VMWARE no la certifica para sus servidores ESX.
Por otro lado si se elige una implementación de un target iSCSI sobre un sistema operativo, ésta solución no tiene porqué dejar de ser soportada por la distribución, ejemplo de ellos son: RHEL que incluye desde la versión 5.3 soporte para esta característica integrando SCSI Target Framework proyecto integrado en la linea principal de desarrollo del Kernel y mantenido por el creador de IET u OpenSolaris/Solaris Express 11 con el proyecto COMSTAR.
En Almacenamiento Abierto hemos diseñado cabinas de discos para entornos de producción con las siguientes características:
Ubuntu Server / SCST / LVM2 / MDADM (RAID 5) / HOT SPARE / ESX/ESXi 4/ MULTIPATH Nativo iSCSI/ SATA
Su aplicación para entornos de producción es un punto de interés fuerte por eso le hemos dedicado una serie de artículos sobre el proyecto SCST.
Si estás interesado en una implementación de targets SCST de bajo Tier certificado para VMWARE u otro entorno quizás te podamos ayudar, o si ya has implementado una o estás en en el proceso, nos gustaría conocer tu experiencia.
Hi my loved one! I wish to say that this article is awesome,
great written and include approximately all important infos.
I’d like to look more posts like this .
Its such as you learn my mind! You seem to grasp so much about this,
like you wrote the e book in it or something.
I think that you simply could do with some p.c.
to drive the message home a little bit, but instead of that, this is magnificent blog.
An excellent read. I’ll definitely be back.
Excellent, what a web site it is! This webpage gives helpful data to us, keep it up.
It’s fantastic that you are getting ideas from this post as well as from our discussion made
here.
Appreciate the recommendation. Will try it out.
If you would like to get a good deal from this
paragraph then you have to apply such techniques to your won web site.
Thank you for some other informative site. Where else could I
am getting that type of information written in such an ideal approach?
I’ve a undertaking that I’m simply now working on, and I’ve been on the look out for
such information.
Hi! I’m at work browsing your blog from my new apple
iphone! Just wanted to say I love reading through your blog and look forward
to all your posts! Carry on the excellent work!
I am regular visitor, how are you everybody? This post
posted at this web page is really pleasant.
Woah! I’m really loving the template/theme of this website.
It’s simple, yet effective. A lot of times it’s hard to get that «perfect balance» between user friendliness and visual appearance.
I must say that you’ve done a amazing job with this.
Additionally, the blog loads super fast for me on Opera.
Superb Blog!
Ahaa, its nice discussion on the topic of
this paragraph here at this blog, I have read all that, so
now me also commenting here.
Outstanding quest there. What occurred after?
Thanks!
It’s remarkable to visit this web site and
reading the views of all colleagues regarding this post,
while I am also zealous of getting familiarity.
It’s amazing in support of me to have a web site, which is good designed for my knowledge.
thanks admin
Hello my loved one! I want to say that this post is awesome,
nice written and come with approximately all vital infos.
I’d like to look extra posts like this .
wonderful submit, very informative. I ponder why the other specialists of this sector don’t realize this.
You should continue your writing. I’m confident, you’ve
a great readers’ base already!
This is really interesting, You are a very skilled blogger.
I have joined your feed and look forward to seeking more of your fantastic post.
Also, I have shared your website in my social networks!
I’ll immediately snatch your rss feed as I can not
in finding your e-mail subscription link or newsletter
service. Do you’ve any? Please let me realize in order that I may subscribe.
Thanks.
Hmm is anyone else encountering problems with the images on this blog loading?
I’m trying to determine if its a problem on my end or if it’s
the blog. Any feedback would be greatly appreciated.
Hello, I enjoy reading all of your article. I wanted to write a
little comment to support you.
Very nice article, exactly what I needed.
Thanks in favor of sharing such a pleasant thought,
paragraph is fastidious, thats why i have read it fully
Spot on with this write-up, I seriously believe that this web site needs much more attention. I’ll probably
be back again to read more, thanks for the info!
Hello, i think that i noticed you visited my web site thus i got here to return the favor?.I’m trying to find
issues to improve my site!I suppose its good enough to use
a few of your concepts!!
Useful info. Lucky me I discovered your website by accident,
and I am surprised why this twist of fate didn’t came
about earlier! I bookmarked it.
Howdy very nice website!! Guy .. Excellent .. Wonderful ..
I’ll bookmark your website and take the feeds additionally?
I’m satisfied to search out numerous useful info
here within the put up, we need work out extra strategies in this regard, thanks for sharing.
. . . . .
I know this if off topic but I’m looking into starting my own weblog and was curious what all is needed to get
set up? I’m assuming having a blog like yours would cost
a pretty penny? I’m not very internet smart so I’m not 100% positive.
Any recommendations or advice would be greatly appreciated.
Thank you
Magnificent beat ! I wish to apprentice at the same time as you amend your web site, how could i subscribe for
a blog website? The account helped me a applicable deal.
I have been a little bit acquainted of this your broadcast
offered vivid transparent concept
Hello there! This is my first visit to your blog! We are a team of volunteers and starting a new initiative in a community in the same niche.
Your blog provided us valuable information to work on. You have done a wonderful
job!
Excellent way of telling, and nice piece of writing to get information on the topic of my presentation focus, which i am going to convey in school.
Good replies in return of this matter with firm arguments and explaining the whole thing about that.
I like the valuable information you supply on your articles.
I’ll bookmark your blog and take a look at once more right here regularly.
I am quite sure I will be informed lots of new stuff right here!
Best of luck for the following!
Your style is unique compared to other folks I’ve read stuff
from. I appreciate you for posting when you have the opportunity, Guess I will just bookmark this web
site.
Excellent post! We will be linking to this particularly great content on our website.
Keep up the good writing.
I got this website from my pal who told me about this
web page and at the moment this time I am visiting this site
and reading very informative articles here.
I love your blog.. very nice colors & theme.
Did you design this website yourself or did you hire someone to do it for you?
Plz reply as I’m looking to create my own blog and would like to find out
where u got this from. appreciate it
Your mode of explaining everything in this paragraph is genuinely fastidious, every one be
able to easily be aware of it, Thanks a lot.
I couldn’t resist commenting. Very well written!
Aw, this was a very good post. Spending some time and actual effort to generate a very good article… but what can I say… I hesitate
a lot and never manage to get nearly anything done.
Thanks in support of sharing such a good opinion, article is fastidious, thats why i have read it entirely
Nice weblog here! Also your site rather a lot up fast!
What web host are you the usage of? Can I get your affiliate link in your host?
I desire my site loaded up as fast as yours
lol
This post is truly a nice one it assists new the web people, who are wishing in favor of blogging.
This site truly has all the information and facts I needed about this subject and
didn’t know who to ask.
Very energetic blog, I loved that bit. Will there
be a part 2?
I really like your blog.. very nice colors & theme. Did you make
this website yourself or did you hire someone to do it for you?
Plz reply as I’m looking to design my own blog and would like to
find out where u got this from. many thanks
Great delivery. Great arguments. Keep up the amazing work.
Hey There. I found your blog using msn. This is a very well written article.
I’ll be sure to bookmark it and come back to read more of your useful info.
Thanks for the post. I’ll certainly return.
You ought to be a part of a contest for one of the
best sites on the web. I’m going to highly recommend this website!
I love what you guys are usually up too. This sort of clever
work and exposure! Keep up the very good works guys I’ve included you guys to our blogroll.
I’ve been exploring for a bit for any high quality articles or blog posts in this
kind of area . Exploring in Yahoo I at last stumbled upon this site.
Reading this information So i am satisfied to convey that I have an incredibly excellent
uncanny feeling I came upon exactly what I needed. I
so much surely will make sure to do not put out of your mind this site and provides it a look on a constant
basis.