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27

I hate to say "don't use SATA" in critical production environments, but I've seen this situation quite often. SATA drives are not generally meant for the duty cycle you describe, although you did spec drives specifically rated for 24x7 operation in your setup. My experience has been that SATA drives can fail in unpredictable ways, often times affecting the ...


23

SAS=SCSI=manageability, especially under load and also better prefailure diagnostics and tuning capability. Spendy and low capacity/£$€. SATA=value, capacity and adequate performance for many loads but be aware that 99%+ of SATA drives aren't designed to work 24/7/365 under duress. Also putting them under busy server workloads can dramatically affect their ...


19

Reevaluate where you're quoting these items and see what the realistic purchase prices are. I often deploy the HP StorageWorks D2700 and D2600 enclosures and populate them with HP-specific drives. I pay less than $1,000 US for each base unit (without disks). The real cost is in the disk drives. These are usually available in bundles with the enclosure ...


18

SAS is active. It is a Network. a 24 drive enclosure likely has 3 backplanes, each driving 8 drives, chained, and everyone of the them is ACTIVE. It has a full SAS Management chip. As such, it has a CPU, it has some RAM, it has Firmware on every of those backplanes. SuperMicro sells a 5.25" to 2.25" enclosure (put it into two 5.25" Slots) and it costs ...


16

A few items to help clarify SAS technology... SATA drives can connect to SAS ports. SAS drives cannot connect to SATA ports. Server-class hardware typically uses an embedded RAID controller or a separate RAID controller PCIe device. Most RAID controllers and SAS HBAs will use SAS connections (multilane or 4-lane SAS ports). Internally, these systems will ...


14

There are two separate parts to your question. Simplifying a bit, a disk consists of the hardware and the controller. Usually when people say "SAS" or "SATA" they are referring to the controller. In principle SAS is a more sophisticated protocol, though in practice for servers with up to say 8 disks there probably isn't much difference between them. Re the ...


14

In addition to the problems above, you may have additional issue running these drives in RAID configuration due to the lack of TLER. (If you are considering a model without.) This quote references desktops and the RAID Edition drives but I imagine the same to be true in the 2.5" line if you substitute in "notebook" and "enterprise" or "SAS" where ...


13

The Storageworks MSA60 enclosure has a "soft" power button. It does not power on automatically. When the power cables are connected, the unit defaults to a standby state. Here's the rear of the HP StorageWorks MSA60 enclosure... On the right side of the rear of the unit, there's a module next to the right power supply which has a soft power button in ...


12

The biggest difference? Failure-rate. Those 'enterprise' drives are warrantied for 5 years, whereas the cheaper ones are probably warrantied for less. Also look into the spec-sheets for them and look at their duty-cycles. The Enterprise drives are designed to run for 5 years straight, where the 'desktop' drives are designed to run 8 hours a day for 5 ...


12

How can a single disk bring down the array? The answer is that it shouldn't, but it kind of depends on what is causing the outage. If the disk were to die in a way that behaved, it shouldn't take it down. But it's possible that it's failing in an "edge case" way that the controller can't handle. Are you naive to think this shouldn't happen? No, I don't ...


12

It works. SATA discs are compatible with SAS. I have tons of them in SAS backplanes. Work like a charm.


12

2.5" hard drives have a much smaller platter diameter and thus there is a smaller mass that must be moved while friction is reduced as well. On the other hand, the operating range of the slider (which carries the heads) is smaller, which has a positive impact on access time if you compare 3.5" and 2.5" at equal rotation speeds and mechanical components. A ...


11

Marketing. 7.2K drives are slower and easier to produce, and with higher error thresholds which improves yields (and capacity). However, in terms of I/O operations each discrete disk can support, the 7.2K drives are markedly less performant than their faster brethren. Therefore they get the 'Nearline' moniker, as they'll hit I/O saturation much faster than ...


11

You have just learned two very important lessons the hard way: RAID is not a backup (and RAID 0 is just a way to increase your chance of failure). If you value your data, MAKE REGULAR BACKUPS and perform frequent restore tests to be sure you can get the data back. At this point if the failed drive isn't even recognized by your system your options are ...


11

This has been covered here... See the related links on the right pane of this question. Right now, the market conditions are such that you should try to use SAS disks everywhere you can. Enterprise SAS disks are your fastest and most resilient rotating media available at 10,000 and 15,000 RPM. Performance-optimized Nearline or Midline SAS are usually ...


11

Based on your problem description your issue isn't so much the server as the storage. You want a reliable, robust filesystem like ZFS that's designed to handle large storage capacity well, and has built-in management capabilities to make that end of the system easier to manage. As was mentioned in the comments, I'd go with ZFS for the storage pool (probably ...


9

SAS is largely an "enterprise" tech whereas USB is most definitely not (at least as far as storage goes, anyway). I'm guessing this is why you haven't found any suitable adapters. That said, you're going about this the wrong way. With a good backup regimen, you dont need the original hardware. So, get a good backup system in place and this issue is ...


9

The "SATA = 7.2K RPM, SAS = 10/15K RPM" mind-set is strong, and (in my opinion anyway) where most of the "SAS is faster than SATA" thinking comes from. There are some slight differences between SAS and SATA drives, notably in their on-board caching algorithms (NCQ vs. TCQ). However, the performance difference of equivalently specced hard-drives will be ...


9

IOPs is the difference your looking for in the "speed". The simple way to explain the difference is that SATA is half duplex and SAS is full duplex. SATA drives are dumb and have to communicate with the controller for operations. SAS drives are smart and only requests and returns use the bus. Depending on your usage case, spending more may not gain ...


9

Great answer by 1138 but one other aspect of note is that midline driveS usually do not have a '24/365' duty-cycle, this is often hard to spot in the specs but it means that if you drive the disks long and hard they'll fail FAR more frequently than you'd think. As an example we had a ~200 disk array full of 1TB MDLs and saw a >20% failure rate in the first ...


8

Your performance sounds about right. The P812 is a 6Gb card, and you're getting consistent 4Gb performance in a RAID10 configuration. Pretty strong, especially with only one enclosure and one pair of SAS channels in use. It shows both channels are actually being used, otherwise your performance would be closer to 375MB/s. In order to get more performance, ...


8

You're going to need a host with a SAS controller or an eraser appliance that supports SAS. As Chris S is pointing out, you can use SATA drives with SAS controllers, but not the other way around. As far as secure deletion, one pass with zeros will stop the amateurs, if you're worried about a TLA, make it one pass with random data, more if you're ...


8

I would avoid NAS's. It's just a 'paranoia' thing with me. If you have even 1k to spend, it'd be easy enough to build a basic system (Even new) and load it with 4 or 5 500GB drives, all raided together (My Personal Favourite is Raid-5). In Raid 5 you'd get near 1.5 TB's. If you just did Striping you'd get 2 ~ 2.5 TB's. And then you have a system you can use ...


8

From Wikipedia: SAS offers backwards-compatibility with second-generation SATA drives. SATA 3 Gbit/s drives may be connected to SAS backplanes, but SAS drives may not be connected to SATA backplanes.


8

I believe that Womble's comment to Peter Schofield is the best observation here...these aren't true SAS disks. No doubt you're being sold "nearline SAS", which is where they take a SATA disk and put a SAS interface on it. The drive mechanics are identical to the SATA version; only the interconnect has changed. When you plug a nearline SAS drive into a ...


8

My two cents: If you are concerned about the edge case failures that may occur with SATA hardware (specifically, lousy SATA controllers), spend the money on real SAS disks. These cards do what they say on the tin: They translate SAS (SCSI) commands to SATA commands, and even implement a few themselves (like power- and spinup-control). They do nothing else ...


8

Your question is somewhat interesting - in that there are actually 3 problems: A unit conversion problem Reserved blocks for the file system (visible by df) Reserved blocks for the file system (not visible by df) Note: I am going to use numbers pulled from one of my systems, not your numbers, since more information is required - the same math applies ...


8

The other guys have answered very well but I have a pet-subject that I like to roll out whenever this kind of thing raises its head - what's known as 'Duty Cycle'. 'Duty Cycle' is the workload that the disk manufacturer anticipates the disk will use and it designed to work most reliably at. For instance many 'enterprise' disks have a 100% 'duty cycle' - ...


8

The idea with ZFS is to let it known as much as possible how is disks are behaving. Then, from worst to better: Hardware raid (ZFS has absolutely no clue about the real hardware), JBOD mode (The issue being more about any potential expander: less bandwidth), HBA mode being the ideal (ZFS know everything about the disks) As ZFS is quite paranoid about ...


8

A few items... You obviously will not be able to address all of them with your existing P410 controller, but: *Do you need all 16 drives in one array?* I ask, because there isn't much utility in having that many disks in a single array unless you know your read/write patterns and are designing around it. If you don't need all 16 disks in a single array, ...



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