Raid5 Sata Available In Thailand?

[Phil Conners]

I'm looking for a RAID5 SATA controller + port replicator. I find lots of options in USA (all made in Taiwan btw) but I'd rather try to avoid the hassle of trying to get it through customs here.

Although I have asked all the shops in Tukcom Pattaya they don't even know what I'm talking about.

Anyone know if/where I can find this in Thailand?

[Guest Reimar]

I'm looking for a RAID5 SATA controller + port replicator. I find lots of options in USA (all made in Taiwan btw) but I'd rather try to avoid the hassle of trying to get it through customs here.

Although I have asked all the shops in Tukcom Pattaya they don't even know what I'm talking about.

Anyone know if/where I can find this in Thailand?

Check with STC at Pantip Plaza. Tel.: 02 656 6127-8, 02 6565532

Shop is at Pantip 3. floor, Room: 325-6. Ask for Kuhn Visan. Ckeck also the Website at: http://www.stccom.com

[Firefoxx]

I remember seeing Promise RAID controllers being sold in Pantip. Perhaps it's the same place that Reimar is talking about. Mine, I got a friend to carry in.

[Phil Conners]

Had a google and found a discussion about SOHO "cheapo" raid5 solutions on Slashdot and it seems the consensus is the best solution is either to get good quality brand name controllers to be able to replace it if (when) it breaks - or simply make a cheap Linux based software raid box. I'm probably going to go with the latter. I've promised my daughter an LCD screen for her computer and Tukcom is giving one away with a PC for 9900 next weekend... might just take that and make it into a raid5 fileserver. It will probably be both cheaper and more reliable than a hardware solution

One question: If you start with a 3 drive raid5 setup, can you add more drives as you need more space without reformatting the whole thing?

PS. Just got this from STC: We have only SR6600-5S-U3, support raid 0,1,3,5,6 spare, 5 SATA drives and

Raid controller build-in, price is almost 60,000 baht.

Edited April 21, 2007 by Phil Conners

[autonomous_unit]

The behavior you are talking about is called "reshape" in the Linux software RAID lingo. It is apparently available as of kernel 2.6.17 and recent mdadm versions to support it. I'd suggest browsing around on these keywords "raid5 mdadm reshape" to get a feel for the state of things. Given that this is new support done in the past 6 months, I'd be cautiously optimistic about trying it. You do keep backups of your raid sets too, don't you?

In the past, I've always taken care to make a set of RAID5 volumes that span the same disk set, and keep my files split over multiple mount points. This way, I could manually reshape by shifting one volume's contents into free space on another volume, then destructively reshaping one volume at a time, formatting, and shifting the content back into place. This requires having enough free space to work with and some carefuly thought to make sure the whole activity will not paint you into a corner...

Some people even do this via LVM e.g. put one large, growable filesystem across a set of RAID5 volumes, so they can just unpin and restore one RAID5 section at a time underneath the single large LVM volume. This always seemed like one too many layers for my taste, as it obfuscates the risk of managing the free space underneath...

One note, all of these methods require a complete read/write cycle on all disks to rearrange the parity. Don't expect the reshape to go quickly. Making this slow process safe across crashes/reboots/etc has been one of the things making it slow for development of the feature.

[Guest Reimar]

Had a google and found a discussion about SOHO "cheapo" raid5 solutions on Slashdot and it seems the consensus is the best solution is either to get good quality brand name controllers to be able to replace it if (when) it breaks - or simply make a cheap Linux based software raid box. I'm probably going to go with the latter. I've promised my daughter an LCD screen for her computer and Tukcom is giving one away with a PC for 9900 next weekend... might just take that and make it into a raid5 fileserver. It will probably be both cheaper and more reliable than a hardware solution

One question: If you start with a 3 drive raid5 setup, can you add more drives as you need more space without reformatting the whole thing?

PS. Just got this from STC: We have only SR6600-5S-U3, support raid 0,1,3,5,6 spare, 5 SATA drives and

Raid controller build-in, price is almost 60,000 baht.

It looks like very expensive. But compare with Promise Controllers!

Have you take a look at: http://www.raidon.com.tw/SR6600-5S-U3_en.pdf ? If not you should do so and than you know where the price came from!

Professional system cost it's money, that's not new! Anyway it's everytime depends you need the thing's for what?!

STC is a company with mainly professional equipment and they didn't deal with "cheapo's"! An unlike many other dealers, STC has a exelent service for "after sales"!

And in my opinion, someone who's looking for professional staff looks for quality for money as well and not for "quantity"! What I mean is: Professional Eqipment is never cheap, has high quality, is sold in low quantity because of it's price and therefore isn't cheap! Products for "home use" produce in high quantity, in mainly lower quality and therefore sold for low price!

But again: take a look at real spec of the SR6600 and after that, count togehter how much a ifferent sys with exactly same spec will cost! I believe you'll wonder!

[Phil Conners]

It's just for private stuff, my mp3 and avi stash among other stuff ... no, can't be bothered to do backups of a TB worth of data doing some 4 GB at the time on DVDR's that may or may not be readable when they're needed. The objective is only to not lose stuff due to a broken disk.

I'm familiar with LVM, it's a fairly mature product so I'm not too worried about that. Will of course have to do some reading on the latest in software raid, that'll be for tomorrow tho, tonights for going out for the first time since songkran

Edited April 21, 2007 by Phil Conners

[think_too_mut]

I'm looking for a RAID5 SATA controller + port replicator. I find lots of options in USA (all made in Taiwan btw) but I'd rather try to avoid the hassle of trying to get it through customs here.

Although I have asked all the shops in Tukcom Pattaya they don't even know what I'm talking about.

Anyone know if/where I can find this in Thailand?

Is it a household use of disks?

Are you sure you want that kind of protection (RAID-5)?

Or only better performance (speed) for viewing/listening to large files?

[youngkiwi]

We have had very bad experiences with Promise RAID controllers. They are somewhat unreliable and I wouldn't recommend them. I suggest a 3Ware card.

[Phil Conners]

I think 3ware was also what was recommended on /.

Yes I'm quite sure I want raid5. No problem putting in a disk to get redundancy on 4.

[youngkiwi]

Do you really need RAID 5? With the large drives now available (up to 750GB - Western Digital), unless you have requirements for very large storage, you could go with a two drive RAID 1 array which offers complete redundancy. RAID 5 is more difficult to rebuild if you have a disk failure, in comparision to RAID 1 so for SOHO use, I'd suggest RAID 1 as an alternative.

If you are passing through Singapore, there are a number of speciality stores at Sim Lim Square (equivalent of Pantip Plaza) which have a wide range of RAID controllers/systems at rock bottom prices.

[endure]

Do you really need RAID 5? With the large drives now available (up to 750GB - Western Digital), unless you have requirements for very large storage, you could go with a two drive RAID 1 array which offers complete redundancy. RAID 5 is more difficult to rebuild if you have a disk failure, in comparision to RAID 1 so for SOHO use, I'd suggest RAID 1 as an alternative.

If you have a decent RAID controller with hotswap drives rebuilding a RAID5 array is no more difficult than pulling the old drive and sticking a new one in. If you can run to an extra hotspare drive it's not even time critical.

[youngkiwi]

From an administrative point of view, rebuilding a RAID 5 array can be much more difficult after disk failure, especially when a unrecoverable sector is found on any of the remaining drives.

[autonomous_unit]

I would argue that RAID5 is no worse than RAID1 in the case of "disk errors on the remaining disk(s)". You get that, and you are screwed and should have used RAID6 or and/or spare drives. The advantage of RAID5 is no more and no less that you get to have N-1 disks' worth of usable space. And, with software RAID5, you avoid the challenge of getting expensive replacement controllers. You can literally just toss the drives into any old Linux box and have the RAID volumes auto-detected and reassembled. I have been very happy running Linux software RAID5 volumes on fileservers running Red Hat and Fedora (just what I historically used).

Unlike some hardware RAID5, a good way to think of software RAID5 on Linux is that you are making individual RAIDed partitions and not an entire RAIDed disk. You do not usually create partitions within such a volume. You can even use different RAID levels on different slices. For example, my usual setup is to have a RAID1 set across all drives for holding /boot, and RAID5 sets for holding / and /home and so on. I configured the /boot to mirror and keep the other drives as spares, so it will automatically rebuild the mirror on a spare if one of the main mirror partitions were to fail. I manually install the bootloader (GRUB) to all drive's MBRs so that it can boot as long as I move one of the good drives to the controller port that the BIOS uses as the boot disk. I do not tend to operate the RAID5 sets with spares, because I usually do RAID5 with just three disks.

In practice, I've had one "catastrophic" failure on a fileserver that had been running unattended for months. One SATA controller port lost its marbles and disappeared from the OS, ejecting that drive from all RAID sets. Then, one of the remaining drives actually developed bad blocks before I noticed this! Then, to top it off, it got rebooted by an eager assistant and the OS tried to fsck the volume that was running with just the one good drive and the one with bad blocks. This caused it to break the array and since the other drive had been forgotten, that one no longer was in sync with the remaining good drive and rebuild was impossible.

The saving grace was that because each drive was sliced into partitions, only the / filesystem was destroyed in this process. The /home partitions on each of the remaining good drives were still untouched because the system tried to fsck the / filesystem first and never made those other writeable. So, reinstalling the OS was sufficient to recover and then let the OS rebuild the data volumes on a new replacement drive. As drives get larger, this use of smaller RAID5 slices is valuable as the drives often develop bad blocks in just small regions at first, and you do not need to eject all partitions immediately (even though you should replace the drive ASAP). This means there is less chance of multi-disk failures affecting a particular volume... you might be able to rebuild different volumes with their good partitions off of different mixtures of partially-bad drives.

Running LVM on top of this can help recombine the slices into larger spaces, but I personally would feel more confident with my bulk data split into separate file trees on each volume, so I can at least be certain to recover one sub-tree at a time if I really did not keep backups. In practice, I actually keep local backups on the same RAID set (to protect against accidental deletes) and then rsync-based mirrors to another similarly configured system at another location (to protect against OS corruption, fire, flood, etc).

One last comment: if you do go with software RAID, it is good to enable the periodic SMART tests that will cause drive surface scans to happen. This will help force bad blocks to be detected early, rather than the first time you try to access some infrequently used bulk data. This helps minimize the chance of data loss since you can replace the drive before more problems sneak up on you.

[youngkiwi]

It is a known fact that software RAID requires more cpu cycles and memory than a comparable hardware RAID system. Software RAID uses the system processor, and all raid functions are performed in the operating system device driver, while hardware RAID uses the onboard RAID controller processor which offers superior performance over software RAID.

While many users have implemented software RAID without issues, I would not recommend software RAID be used for production machines. If you are looking for the best reliability and performance, choose hardware RAID any day over software RAID alternatives. We exclusively use 3Ware RAID cards and speaking from experience, I can highly recommend them.

[autonomous_unit]

Yes, this software RAID discussion was predicated on budget solutions for home storage for very technical folks, not production business use. But, I guess I would question the use of nearly any of the RAID cards in a PC, once you cross the threshold from cheap commodity stuff. Things like the Apple X-Serve chassis are just too affordable and attractive once you really need some redundancy of controllers, power supplies, and even server hosts, and you're actually going to be managing a growing disk pool.

For geeks who want a cheap and effective RAID5 solution, and who can handle their own tech support, the Linux software RAID can be very nice. As Phil pointed out, it can be cheaper to outfit a fast enough PC to act as a network file server over gigabit ethernet, rather than bothering with storage cards which can start costing as much as the PC. This works great for "near-line" storage of movies, music, and digital photo archives where you do not need bleeding edge performance, but just cheap trustworthy storage.

My personal experience is that software RAID5 on locally attached disks is fast enough to not care about the CPU overhead on a modern Athlon64 or Core2 Duo system. And it is more than sufficient to fill gigabit ethernet to capacity using NFSv4, without the CPU ever scaling out of its lowest clock speed on the file server.

[endure]

From an administrative point of view, rebuilding a RAID 5 array can be much more difficult after disk failure, especially when a unrecoverable sector is found on any of the remaining drives.

If 2 drives fail it will make no difference whether you're using RAID5 or RAID1. As I said if you're using a decent RAID controller like an LSI or one of the HP controllers it's simply a matter of swapping the bad for the good. The controller will usually let you know that a drive is degrading long before it fails.

[steffi]

That's the guy with the big Malaysian fish in his shop right? I bought a firewire 400/800/USB2.0 enclosure from there last year. A truely satisfying experience. He probably won't have brandname brandname since a lot of what he sells is Taiwanese made. my enclosure was Mapower.

I'm looking for a RAID5 SATA controller + port replicator. I find lots of options in USA (all made in Taiwan btw) but I'd rather try to avoid the hassle of trying to get it through customs here.

Although I have asked all the shops in Tukcom Pattaya they don't even know what I'm talking about.

Anyone know if/where I can find this in Thailand?

Check with STC at Pantip Plaza. Tel.: 02 656 6127-8, 02 6565532

Shop is at Pantip 3. floor, Room: 325-6. Ask for Kuhn Visan. Ckeck also the Website at: http://www.stccom.com